This Schlieren image of a butane torch shows the flow structure of the gas as it burns Schoegl’s invention could help shortcut the design process About LSU’s Office of Innovation & Technology Commercialization For licensing inquiries, contact techlicensing@lsu.edu Boom Supersonic has released Schlieren imagery of the shock waves created by its XB-1 demonstrator aircraft during test flights last month NASA researchers on the ground used Schlieren photography to visualize the shock waves created during XB-1’s second supersonic flight on February 10, 2025. In January XB-1 became the first independently developed jet to fly faster than the speed of sound and the first civil supersonic jet built in America NASA teams also collected data on XB-1’s acoustic signature at one location on the flight route Boom’s analysis of the data found that no audible sonic boom reached the ground as the jet flew at supersonic speeds “This image makes the invisible visible—the first American-made civil supersonic jet breaking the sound barrier,” said Blake Scholl “We also confirmed that XB-1 made no audible sonic boom which paves the way for coast-to-coast flights up to 50% faster.” Taking Schlieren images requires ideal conditions and timing Boom Chief Test Pilot Tristan “Geppetto” Brandenburg positioned XB-1 at an exact time in a precise location over the Mojave Desert to enable NASA to photograph XB-1 flying in front of the sun documenting the changing air density around the aircraft at speeds exceeding Mach 1 the XB-1 team rapidly developed avionics software to guide the pilot to the specific points in space that XB-1 would have to fly through in order to eclipse the sun NASA used ground telescopes with special filters that detect air distortions Efforts conducted by both NASA and Boom while modeling the expected flight parameters of XB-1’s supersonic flights estimated a very high likelihood of operating at Mach cutoff in which a sonic boom refracts in the atmosphere and never reaches the ground This effect is achieved by breaking the sound barrier at a high enough altitude with exact speeds varying based on atmospheric conditions Sonic boom data was captured with microphones and sound pressure level recording devices positioned in limited strategic locations in relation to the flight path Boom’s assessment of this type of data from XB-1’s supersonic flights demonstrates that supersonic flight without the disturbance of a sonic boom is possible This aligns with research previously conducted by NASA in efforts to bring supersonic commercial travel to the public Boom plans to use data collected from XB-1’s test flight program to bring what it is terming “boomless cruise” to the supersonic airliner it is developing The Mach 1.7-capable Overture airliner will carry up to 80 passengers with a range of 4,900 miles (7,885km) The aircraft will be powered by three non-afterburning The company has 130 orders and pre-orders from United Airlines Boom completed construction on the Overture Superfactory in Greensboro which will scale to produce 66 Overture aircraft per year Get the 'best of the week' from this website direct to your inbox every Wednesday Metrics details Non-linearities in organic exciton-polariton microcavities represent an attractive platform for quantum devices progress in this area hinges on the development of material platforms for high-performance polariton lasing and ultimately strategies for electrical pumping we show how introducing Schlieren texturing and a rough intra-cavity topography in a liquid crystalline conjugated polymer enables strong in-plane confinement of polaritons and drastic enhancement of the lasing properties In high-Q distributed Bragg reflector microcavities polariton lasing was observed at unprecedented thresholds of 136 fJ per pulse Morphology tuning also permitted polariton lasing in more lossy metallic microcavities while maintaining a competitive lasing threshold The facile fabrication of these cavities will drastically reduce the complexity of integrating polariton lasers with other structures and the high conductivity of metallic mirrors may provide a route to electrical pumping this also enabled out-of-equilibrium Bose-Einstein Condensation (BEC) This additional level of control over the light path within the cavity might therefore provide an alternative strategy to also achieve lateral confinement in polariton lasers therefore making it a favorable environment for multiple scattering events at the microscopic scale we introduce Schlieren textures with characteristic domain sizes <10 µm in films of the LCCP poly(9,9-dioctylfluorene) (PFO) using a scalable bottom-up approach Using a subtle interplay between the local dipole orientation and the intra-cavity topography originating from these Schlieren textures we achieve in-plane confinement of polaritons discontinuities in refractive index at domain boundaries together with an average roughness for the active layer of Ra = 2.6 nm lead to a drastic improvement in polariton laser performance This performance increase allows us to replace the electrically insulating distributed Bragg reflectors (DBRs) that are conventionally used to form the microcavity by highly conductive metallic mirrors Metallic mirrors were previously unsuitable for polariton lasers due to their lower reflectivity (e.g. ~95% reflectivity for silver compared with >99.9% for DBRs) The deposition of metallic mirrors via thermal evaporation is substantially simpler and more rapid (tens of minutes) than the fabrication of DBRs metallic mirrors also offer a direct pathway for charge injection in future electrically pumped polariton lasers We then elucidate the specific role of the rough topography of the cavity and utilize the improvement in threshold afforded by the Schlieren texture to realize anisotropic polariton lasing in a hybrid metal/DBR cavity with a threshold of \({P}_{{{{\rm{th}}}},{{{\rm{Ag}}}}/{{{\rm{DBR}}}}}=2.67\,{{{\rm{pJ}}}}\) per pulse as well as in a metal/metal cavity with \({P}_{{{{\rm{th}}}},{{{\rm{Ag}}}}/{{{\rm{Ag}}}}}=15.19\,{{{\rm{pJ}}}}\) per pulse the performance of the purely metallic polariton laser is on par with current state-of-the-art DBR-based polariton lasers Careful analysis of the hallmarks of polariton lasing—in particular linewidth and blue-shift—for the different types of mirrors reveals a subtle interplay between lasing threshold and surface roughness a Illustration of protocol for forming Schlieren textured active layers of PFO with 15% β-phase content Chemical structure of the β-phase chain conformation of PFO shown in blue Polarized transmission optical micrograph of the resulting film placed between a crossed polarizer (P) and analyzer (A) pair No light is transmitted when the exciton transition dipole moment lies perpendicular to either the polarizer or analyzer while maximum transmission occurs when the transition dipole moment lies at 45° relative to both the analyzer and polarizer b Polarized optical micrograph (top) and corresponding emission under non-resonant polarized excitation (false color The dashed red circle indicates an area of confined emission c Proposed working principle of the Schlieren textured polariton laser: Rough intra-cavity topography combined with local orientation gives rise to in-plane confinement with the cavity mirrors providing vertical feedback d Schematic structure of the dielectric DBR/DBR and metallic Ag/Ag cavities used in this study which showed the confinement of the electric field in a circular region of diameter d ~ 3 µm The calculated field overlaps with one of the aligned micro-domains with its amplitude decreasing sharply outside of the domain’s borders similarly to what was observed in the experiment a AFM measurement performed on the surface of the DBR/DBR Schlieren cavity showing an average roughness Ra = 2.6 nm b TMCs of the reflectivity of DBR/DBR cavities with aligned 15% β-phase PFO at the design thickness for a resonance at 2.65 eV (red line) and assuming a 3 nm thickness increase over the design thickness (blue line) The calculation was performed for light polarized parallel to the alignment of the PFO transition dipole moment c Calculated LP energy profile for a randomly generated film topography with a correlation length and amplitude matching the Schlieren cavity measured in (a) d FDTD simulation of the normalized squared electric field 1443 fs after excitation for the LP energy profile shown in (c) e Superposition of data from (c and d) illustrating how the electric field is confined to regions of lower LP energy Taken together with the polarization-resolved experimental data above we conclude that both the micro-domain alignment and the intra-cavity topography contribute to confining the polaritons in-plane in the Schlieren cavity f) show the corresponding real space emission; scale bars The excitation polarization was vertical (\({\phi }_{{{{\rm{pump}}}}}=0^\circ\)) An intensity color scale is given on the right-hand side of each panel The weak background emission observed for the Ag/DBR and Ag/Ag cavities is associated with non-localized emission emanating from the surroundings of the confined spot; it is more visible for the Ag/DBR and Ag/Ag cavities as the excitation pulse energies used for these are more than one order of magnitude higher than for the DBR/DBR cavity no emission was observed when the excitation polarization was set to \({\phi }_{{{{\rm{pump}}}}}=90^\circ\) while keeping the same excitation spot on a 0°-oriented domain; this illustrates how the strong anisotropy of the system enables polarization selection Emission spectra collected over an angular range \(\theta \in [-2^\circ ;2^\circ ]\) for increasing excitation pulse energy transitioning from spontaneous LP emission to polariton lasing LP linewidth (dashed line) and blue-shift of LP peak (solid line) for the DBR/DBR (e) The dashed vertical lines indicate the polariton lasing thresholds for each cavity as determined in (a) the excitation polarization was set to \({\phi }_{{{{\rm{pump}}}}}=0^\circ\) The dependence of integrated emission on excitation energy was analyzed further by fitting a kinetic model for the time evolution of the populations of reservoir excitons An estimate for \({\tau }_{{{{\rm{LP}}}}}\) is obtained from the linewidth of sub-threshold LP emission at \(\theta=0^\circ\) and is referred to as \({\tau }_{{{{\rm{LP}}}}-\exp }\) and Ag/Ag cavities and the corresponding kinetic parameters The radiative decay times fitted with the kinetic model \(({\tau }_{{{{\rm{LP}}}}-{{{\rm{fit}}}}})\) are in close agreement with the decay times extracted from the linewidth of the LP emission below threshold \(({\tau }_{{{{\rm{LP}}}}-\exp })\) increases with the introduction of the Ag mirrors; fDBR/DBR = 0.03 achieved for a DBR/DBR cavity with an active layer of macroscopically aligned 15% β-phase PFO (\({P}_{{{{\rm{th}}}},{{{\rm{Aligned}}}}}=2.23\,{{{\rm{pJ}}}}\)) losses increase further when the top Ag mirror is evaporated directly on the rough polymer layer as the metal film formation is prone to nanocluster formation the density of these lasing spots appears to be lower especially for electrical injection pumped polariton lasing a situation where a high number of scattering events (i.e. a short optical free path) compared to the effective wavevector would halt the propagation of polaritons tuning of the cavity topography might allow to observe a transition between a propagating and halted flow of polaritons PFO was supplied by the Sumitomo Chemical Company The peak molecular weight was \({M}_{{{{\rm{pPFO}}}}}=50\times {10}^{3}\) g mol−1 Ta2O5 and SiO2 were sputtered from >99.99% oxide targets (Angstrom Engineering) The substrates used were display-grade glass (Eagle XG The Rabi-splittings for the Ag/DBR cavity were then approximated using an evenly weighted sum of the DBR/DBR and the Ag/Ag values to give \({{\hslash }}{\Omega }_{1-{{{\rm{Ag}}}}/{{{\rm{DBR}}}}}\approx\) 0.95 eV and \({{\hslash }}{\Omega }_{2-{{{\rm{Ag}}}}/{{{\rm{DBR}}}}}\approx\) 0.1 eV 1 nm Al (as seed layer) was deposited by electron beam physical vapor deposition and Ag was deposited by thermal evaporation in a vacuum chamber (Angstrom EvoVac) at a base pressure of 1 × 10 − 7 mbar Al was used as a wetting layer to improve percolation and optical quality of the thin Ag films SiO2 and Ta2O5 were deposited by radiofrequency magnetron sputtering at a base pressure of 10−7 Torr using 18 standard cubic centimeters per minute (sccm) Argon flow at 2 mTorr process pressure and 18 sccm Argon together with 4 sccm Oxygen flow at 4 mTorr process pressure for SiO2 and Ta2O5 The additional oxygen flow during Ta2O5 deposition prevents the formation of unwanted sub-oxides A layer of PFO was spin-coated using 24 mg mL−1 PFO in toluene solution for the DBR/DBR cavity with an initial acceleration of 1000 rpm s−1 the sample was placed on a precision hotplate (Präzitherm Gestigkeit GmbH) in an inert environment and the temperature was raised from 25 °C to 160 °C at a rate of approximately 30 °C min−1 The upper temperature was then held for 10 min followed by rapid quenching to room temperature by placing the sample on a metallic surface to induce the nematic phase Schlieren texture in the PFO film approximately 15% β-phase fraction was induced in the by exposing the films to a saturated toluene vapor environment for 24 h The thicknesses of the films and thus of the active layers in the final cavity were controlled using a profilometer (Dektak Bruker) on simultaneously prepared reference samples the top DBR or Ag mirror was deposited following the same process described above AFM measurements were performed using a JPK Bruker NanoWizard 4 mounted on a Nikon Eclipse Ti2 inverted microscope FDTD simulations of the in-plane component of \({\left|{{{\boldsymbol{E}}}}\right|}^{2}\) were performed to reproduce the localization of exciton-polaritons inside the active layer The simulations were performed using the FDTD 3D Electromagnetic Simulator from Lumerical-Ansys The data generated in this study are openly available via the St Andrews Research Portal at https://doi.org/10.17630/7382ac95-03eb-4456-ad70-2f3fd1aeae88 Direct determination of the exciton binding energy of conjugated polymers using a scanning tunneling microscope The photovoltaic response in poly(p-phenylene vinylene) thin-film devices Exploring light-matter interaction phenomena under ultrastrong coupling regime Ultrastrong light-matter coupling in electrically doped microcavity organic light emitting diodes Observation of ultrastrong-coupling regime in the Fabry–Pérot microcavities made of metal mirrors containing Lemke dye Ultrastrongly coupled exciton-polaritons in metal-clad organic semiconductor microcavities Room-temperature polariton lasing in an organic single-crystal microcavity Nonlinear interactions in an organic polariton condensate Room-temperature Bose-Einstein condensation of cavity exciton-polaritons in a polymer An exciton-polariton laser based on biologically produced fluorescent protein Room-temperature superfluidity in a polariton condensate A room-temperature organic polariton transistor Single-photon nonlinearity at room temperature Low threshold room temperature polariton lasing from fluorene-based oligomers Low-threshold exciton-polariton condensation via fast polariton relaxation in organic microcavities Ultrafast polariton population build-up mediated by molecular phonons in organic microcavities Longitudinal optical phonon-assisted polariton laser Enhanced light-matter interaction and polariton relaxation by the control of molecular orientation Efficient anisotropic polariton lasing using molecular conformation and orientation in organic microcavities High-performance planar microcavity organic semiconductor lasers based on thermally evaporated top-distributed Bragg reflector Photonic confinement in laterally structured metal-organic microcavities Properties and applications of random lasers as emerging light sources and optical sensors: a review Random lasing in low molecular weight organic thin films Unidirectional high-intensity narrow-linewidth lasing from a planar random microcavity laser Dierking, I. Textures of Liquid Crystals. Textures of Liquid Crystals https://doi.org/10.1002/3527602054 (2003) Sackmann, H. & Demus, D. The polymorphism of liquid crystals. 2, 81–102. https://doi.org/10.1080/15421406608083062 (1966) On the schlieren texture in nematic and smectic liquid crystals Packing and uniaxial alignment of liquid crystalline oligofluorenes Two-photon laser-written photoalignment layers for patterning liquid crystalline conjugated polymer orientation Room-temperature exciton-polariton condensation in a tunable zero-dimensional microcavity Polariton laser using single micropillar GaAs-GaAlAs semiconductor cavities Quantum wires in multidimensional microcavities: effects of photon dimensionality on emission properties Zero- and π-states in a periodic array of deep photonic wires Mechanisms of blueshifts in organic polariton condensates Thermalization of fluorescent protein exciton-polaritons at room temperature Polariton condensation in an organic microcavity utilising a hybrid metal-DBR mirror Lasing of Tamm states in highly efficient organic devices based on small-molecule organic semiconductors Polariton Bose-Einstein condensate from a bound state in the continuum Relating chain conformation to the density of states and charge transport in conjugated polymers: the role of the β-phase in poly(9,9-dioctylfluorene) How β-phase content moderates chain conjugation and energy transfer in polyfluorene films Anderson localization of electromagnetic waves in three dimensions Absence of diffusion in certain random lattices Cavity quantum electrodynamics with Anderson localized modes Random nanolasing in the Anderson localized regime Anderson localization in steady states of microcavity polaritons Efficient bosonic condensation of exciton-polaritons in an H-aggregate organic single-crystal microcavity Enhanced and polarization-dependent coupling for photoaligned liquid crystalline conjugated polymer microcavities Azobenzene sulphonic dye photoalignment as a means to fabricate liquid crystalline conjugated polymer chain‐orientation‐based optical structures Topological insulator vertical-cavity laser array Download references Anna Popczyk for her help with the AFM measurements and Prof Donal Bradley and the Sumitomo Chemical Company for provision of PFO F.L.R acknowledges funding from the Alexander von Humboldt Foundation through a Humboldt Fellowship acknowledges funding from the European Union Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No This research was financially supported by the Alexander von Humboldt Foundation (Humboldt Professorship to M.C.G.) Open Access funding enabled and organized by Projekt DEAL Humboldt Centre for Nano- and Biophotonics wrote the manuscript with input from all authors The authors declare no competing interests Nature Communications thanks the anonymous reviewers for their contribution to the peer review of this work Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41467-025-55875-1 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science Too many automated requests from this network Home → Science → News The coolest thing about this flight is that there was no sonic boom the Boom Supersonic XB-1 test jet roared past Mach 1 NASA captured the moment in a striking image a vivid display of air rippling around the aircraft an optical technique that reveals changes in air density It is a dramatic visual for a future where supersonic commercial travel might return to the limelight after the retirement of the Concorde in 2003 The photograph shows the XB-1 streaking across the sky its silhouette framed by vivid orange streaks and pale yellow exhaust trails the visual fingerprints of an aircraft pushing through the sound barrier is the fact that the technology is over a century old Schlieren photography was first developed in 1864 and relies on the principle that changes in air density — caused by pressure this technique has been mostly confined to lab experiments due to special requirements like a collimated (made parallel) light beam The modern version of this technique is called Background Oriented Schlieren (BOS) which uses a natural textured background (in this case the desert floor) and advanced digital imaging to produce Schlieren images “This image makes the invisible visible,” said Blake Scholl this flight produced another milestone: there was no audible sonic boom on the ground “We confirmed that XB-1 made no audible sonic boom,” Scholl said Sonic booms have long been a barrier to overland supersonic flights The Concorde was banned from virtually every country in the world because of the thundering noise and France allowed the Concorde to enter their airspace and then only to cities in close proximity to the ocean — NYC Boom Supersonic managed to cancel out the loud boom by employing clever flight dynamics When a jet breaks the sound barrier up there This speed difference bends the sound waves upward and prevents the effects from reaching the ground If Boom can consistently minimize or eliminate these booms it could convince regulators to lift restrictions opening the door to faster coast-to-coast flights The XB-1’s success is a critical step toward Overture Designed to carry 64 to 80 passengers at Mach 1.7 and Japan Airlines have placed 130 orders and pre-orders for the aircraft Supersonic travel has always been fraught with false starts and challenges the Boeing 2707 promised a supersonic future only to be derailed by cost overruns and regulatory hurdles while iconic and with over 50,000 flights under its belt limited by its noise and high operating costs But Boom Supersonic is betting that new technologies will make the difference this time The XB-1 is made almost entirely from carbon fiber composites making it lighter and stronger than its predecessors Its augmented reality vision system replaces the Concorde’s heavy droop nose improving pilot visibility without adding weight And Overture is designed to run on sustainable aviation fuel (SAF) aligning with the industry’s push toward greener travel “The advent of digital engineering is a huge enabler for why supersonic flight’s coming back,” Scholl told CNN propulsion: Those are the big three areas where we’ve made huge progress versus Concorde.” © 2007-2025 ZME Science - Not exactly rocket science © 2007-2025 ZME Science - Not exactly rocket science the first civil aircraft to go supersonic over the continental United States "This image makes the invisible visible — the first American made civil supersonic jet breaking the sound barrier." NASA and Boom Supersonic just released an incredible photo capturing a shockwave emanating from the dark silhouette of the supersonic XB-1 aircraft while it traveled in front of the sun during a Feb 10 test flight during which it broke the sound barrier three times It required ideal conditions and perfect timing Chief test pilot Tristan "Geppetto" Brandenburg cut a path to a precise spot over the Mojave Desert while NASA snapped the shot "Thanks to Geppetto's exceptional flying and our partnership with NASA we were able to capture this iconic image," Scholl continued The photo is a Schlieren image Developed in 1864 by German physicist August Toepler to study supersonic motion Schlieren photography is used in today's aeronautical engineering The method can reveal how light bends around differences in air pressure during supersonic flight The XB-1 team made software using NASA data to guide the pilot on a path where the aircraft could eclipse the sun NASA got the photograph using ground telescopes with special filters that detect air distortions That's why the shockwaves around the aircraft are visible in the photograph NASA also gathered sound data from the test flight. Boom Supersonic analyzed the data and found that no audible sonic boom reached the ground. This is notable, because supersonic flights that make sonic booms over populated areas in the U.S Boom Supersonic plans to make a supersonic airplane with a sonic boom that won't disturb people on the ground This airplane would reduce cross-country flight times "We confirmed that XB-1 made no audible sonic boom," Scholl said in the same statement "which paves the way for coast to coast flights up to 50% faster."  —  Boom Supersonic XB-1 jet breaks sound barrier on historic test flight (video)  — Boom Supersonic's XB-1 jet breaks sound barrier 3 times on final test flight (video, photos)  — NASA's new supersonic X-59 jet hits the afterburner (photos) Now Boom Supersonic will take what they learned from the tests and start building a supersonic airliner called Overture Boom Supersonic finished building its super factory in Greensboro North Carolina which will eventually pump out 66 Overture aircraft per year and Japan Airlines already have orders and pre-orders in for the supersonic airliner Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com. Julian DossettSocial Links NavigationJulian Dossett is a freelance writer living in Santa Fe He primarily covers the rocket industry and space exploration and in addition to science writing, contributes travel stories to New Mexico Magazine He graduated from Texas State University in San Marcos in 2011 with a B.A He owns a large collection of sci-fi pulp magazines from the 1960s you will then be prompted to enter your display name Drone pilot who flew over Vandenberg Space Force Base sentenced to 4 months in jail NASA's X-59 quiet supersonic jet clears 'major hurdle' ahead of 1st flight (photos) US House space committee wants a standard lunar clock NASA has released a new image providing photographic evidence of Boom Supersonic's XB-1 prototype aircraft breaking the sound barrier it used a special imaging technique to record the historic event A frustrating aspect of many technological achievements is that you often have to take someone else's word that it happened at all Did Sir Edmund Hillary and Tensing Norgay reach the summit of Mount Everest in 1953 Did Jacques Piccard really visit the bottom of the Mariana trench in 1960 Did Neil Armstrong and Buzz Aldrin set foot on the Moon in 1969 you end up with the old joke that in order to fake the Moon landing you still had to build and launch the giant rocket so the only money the alleged fraud saved was the catering bill We nailed it.During XB-1’s second supersonic flight, we partnered with @NASA to take this Schlieren image of XB-1 pushing through the air at supersonic speeds. Here’s the shot, captured by NASA teams on the ground. It documents the changing air density around XB-1 and the… pic.twitter.com/89HFHQ30W3 it is nice to have direct evidence of something being pulled off instead of just reels of telemetry data In the case of Boom achieving the first commercial supersonic flights the company teamed up with NASA to capture images of the aircraft blasting past Mach 1 using a technique called Schlieren optics you may have seen examples of this technique in school science textbooks to show bullets in flight or the turbulence from the air rising from a candle flame it's more than a way of making cool pictures to entertain bored students waiting for the bell to ring It also provides scientists and engineers with valuable information There are any number of ways to achieve Schlieren images but its basics boil down to using a set of special lights which is reflected onto a screen or through a camera lens to create a very stable image The clever bit is that this image remains stable until the air around it is disturbed like by lighting a candle or having an object flying by at supersonic speeds This produces subtle changes in air pressure The Schlieren image can detect and make these visible because such changes change the air's refractive index and deflects light we can see the heat rising off a human arm or the air being pushed by a butterfly's wings It's all very dramatic and makes for some great science documentary footage it was also confined to the lab bench because of the complicated set up required to create things like the culminated light beam and the necessary background Then around 2000, DLR Göttingen developed a variant called Background Oriented Schlieren (BOS) that uses a natural textured background and digital imaging to produce Schlieren images without the need for special lighting or complex optical bench set ups It achieves this by using a stable background like the desert floor that can be divided into a speckle pattern This is recorded as a reference image and then when an aircraft like the XB-1 flies through the area the displaced air disturbs the pattern which can be measured and turned into an image by way of painfully complicated cross-correlation algorithms The result: XB-1 going supersonic caught on film That may be a nice snap for the history books engineers can confirm and enhance the sonic-boom-deadening properties for the XB-1's airframe It can also be used to look at helicopter rotors or propeller blades and record how aircraft flying in formation disturb one another by mixing air streams And maybe give future students more cool pictures to look at Source: Boom Aerospace with help from the steady flying of Boom Supersonic chief test pilot Tristan “Geppetto” Brandenburg just released a visualization of the phenomenon The company’s XB-1 “Baby Boom”—a demonstrator that is about one-third the size of Overture, a supersonic, SAF-powered airliner it is developing for 64 to 80 passengers—is the first independently built jet to break the sound barrier it eclipsed Mach 1 six times across two test flights But you wouldn’t be able to tell from the ground Boom conducted its test flights under a special flight authorization ‘Thou shalt not exceed Mach one,’” Blake Scholl NASA teams on the ground used specialized telescopes to deploy the Schlieren photography technique which captures changing air densities around a supersonic aircraft as it eclipses the sun to visualize shockwaves while Boom devised avionics software that guided Brandenburg to the exact spot he needed to hit The maneuver also required precise timing and conditions We nailed it.During XB-1’s second supersonic flight, we partnered with @NASA to take this Schlieren image of XB-1 pushing through the air at supersonic speeds. Here’s the shot, captured by NASA teams on the ground. It documents the changing air density around XB-1 and the… pic.twitter.com/89HFHQ30W3 “This image makes the invisible visible—the first American made civil supersonic jet breaking the sound barrier,” Scholl said in an update Monday “Thanks to Geppetto’s exceptional flying and our partnership with NASA we were able to capture this iconic image.” According to Boom, the partners’ analysis “estimated a very high likelihood of operating at Mach cutoff.” The data collected from the effort, the firm said, will help it add boomless cruise capability to Overture, planned as the company’s successor to the famed Concorde Fifty-six years ago on Sunday, Concorde made its maiden voyage. It was retired in 2003 But Boom hopes to bring supersonic commercial flight back by the end of the decade—including operations over land The company claims boomless cruise has the potential to reduce U.S if the FAA can be swayed to change its rules Regulations prohibit all supersonic flights over land Scholl believes it will be “pretty easy” to convince regulators the provision is outdated The Boom CEO said those efforts are already underway Like this story? We think you’ll also like the Future of FLYING newsletter sent every Thursday afternoon. Sign up now By 2025-03-03T21:20:00+00:00 US aeronautics agency NASA managed to capture the Boom Supersonic XB-1 research aircraft as it broke the sound barrier during its final flight on 10 February The flight – the XB-1’s second in excess of Mach 1 – was the last in a series of test sorties by the aircraft conducted to support Boom’s development of the proposed Overture airliner One of the aims of the flight over the Mojave desert was to acquire a Schlieren photograph of the jet at supersonic speed Schlieren photography involves imaging light which has been refracted by changes in the air temperature or pressure Such techniques enable the shockwaves generated by the aircraft to be visualised but the process required NASA to capture the XB-1 passing in front of the sun using ground telescopes fitted with filters Schlieren imaging shows XB-1 flying in excess of Mach 1 over the Mojave desert “This image makes the invisible visible – the first American-made civil supersonic jet breaking the sound barrier,” says Boom Supersonic chief Blake Scholl NASA also obtained acoustic data from the aircraft which demonstrated the ‘boomless cruise’ principle under certain speed and atmospheric conditions Scholl claims the data confirms XB-1, which had also flown supersonically on 28 January is intended to provide an avenue for Overture to achieve overland supersonic flight – currently banned by the US FAA owing to sonic boom disturbance Electric aircraft propulsion specialist Wright Electric is preparing to begin ground testing with the M2500 electric engine it is developing to power commercial aircraft having completed construction of a test stand that will accommodate the trials controllers temporarily lost ability to ”see hear or talk to” pilots flying jets to and from Newark US carrier JetBlue Airways has shed innovation arm JetBlue Ventures to aviation investment group Sky Leasing in a bid to focus more on “core airline operations”.  Lilium’s collapse has claimed another victim with German battery supplier CustomCells – which had pledged to fund the electric air taxi developer’s revival – now itself facing insolvency AALTO has claimed a new stratospheric flight record with its Zephyr High Altitude Platform Station with one of its vehicles having remained airborne for more than two months Qatar Airways’ cargo division is to be the launch customer for the Boeing 777-200LR freighter conversion programme established by US-based Mammoth Freighters The disclosure follows the initial test flight of the prototype converted aircraft (N705DN) following its modification at Aspire MRO in Fort Worth FlightGlobal is the global aviation community’s primary source of news analytics and advisory services to connect the aviation community globally and help organisations shape their business strategies identify new opportunities and make better decisions faster Site powered by Webvision Cloud member-first insights and commentary on the global aviation industry A 28-year-old construction worker died in an accident at work in Schlieren ZH on Wednesday morning The Zurich cantonal police confirmed a corresponding report by BRK News to Keystone-SDA The accident occurred during formwork work on a large construction site An emergency call was made at around 8.20 am FC Union Berlin women's team will face FC Schlieren in their last mid-season friendly The game against the Swiss second division side will be played on Sunday at the Fritz-Lesch Sportsplatz on Dörpfeldstraße FC Union Berlin women's team will face FC Schlieren in their last mid-season friendly FC Schlieren ended their own three-month winter break with a 4-1 defeat to FC Küssnacht at the end of November 2020 Liga will kick off at the end of February for them with a game against FC Lugano Union also lost their second friendly of the winter despite having created more chances against Polish champions Pogon Sczeczin and taking the lead through Naika Reissner.  Ultimately the efficient Polish team managed to turn the game around FC Schlieren have been playing in the National League B since 2012 and are currently in 3rd place the side in blue and yellow are eight points behind the leaders Yverdon Sport FC a separate promotion round takes place in Switzerland after the regular season A return to the top Swiss league after 13 years is therefore still possible the team from the Zürich suburbs will also complete a five-day training camp in the Turkish resort of Side in February They have been coached by the Italian Alessandro Vicedomini since 2021 Union Berlin head coach Ailien Poese will have to do without Sophie Trojahn "We are looking forward to the game of the winter preparation," said Union's head coach "We want to bring the content of the training week onto the pitch again in competition create good scoring chances and take them."  Kick off is at 11:30 am on Sunday at the Fritz-Lesch-Sportplatz on Dörpfeldstraße Union will provide information about the game via the club's live ticker as well as offering updates in English on Twitter Metrics details Light emissions and Schlieren structures were simultaneously observed from streamers produced by tens of kilovolts 1.2/50 μs impulses representing the high voltage component of lightning applied across a 4 cm air gap between a variety of electrode geometries and a ground plane in an unconfined environment The results demonstrated that the light emissions and Schlieren structures coincide along the same streamer filaments but on different timescales; the light existing only during the microsecond timeframe impulse whereas the Schlieren continued to develop into the millisecond timeframe moving towards the centre of the air gap whilst diffusing into the surrounding air within 100 ms the Schlieren structures outside the arc remained visible Streamer formation theory for high voltage impulses is subsequently refined to include the observed Schlieren mechanism Lightning is one of the most powerful and destructive naturally occurring electrical phenomena and the protection of vital infrastructure such as power transmission and transportation from strikes and destructive effects is of great importance it can be very demanding to carry out detailed studies of the underlying mechanisms and characteristics of lightning and related phenomena in the natural environment Laboratories have been developed to study the high current and high voltage components individually which are often used to represent the physically destructive aspects through joule heating and electric field breakdown effects in both conducting and insulating materials This is because the production of a combined high current and high voltage arc as seen in a natural lightning strike are beyond the capabilities of any existing laboratory generator A laboratory high voltage component can consist of impulses up to the megavolt magnitude range but most frequently tens to hundreds of kilovolts are used which last hundreds of microseconds be used to understand whether a power substation component may fail by creating a fault-like overvoltage condition a lightning strike on one part of a power network can result in partial or full discharge events in other parts of the network Applying a high voltage induced field to test such components can determine the insulation strength of an insulating gap such as air or a solid insulation material and provide statistical evidence as to the likelihood of an electrical breakdown to ground The mechanism by which the air breakdown would occur is through the formation of transient streamers within the air gap between the high voltage electrode and ground which could create a conductive channel between the two They are sometimes used interchangeably to derive characteristics but are rarely used simultaneously Although both light and Schlieren imaging can be used to observe the structure and shape of streamers with both being a result of streamer formation the underlying mechanisms for each are very different The emitted light is a result of either the recombination of atoms or Bremsstrahlung radiation and is often visible to the naked eye as a blue-white flash which can be captured by a wide range of cameras Schlieren is an optical effect within the air caused by localised density changes typically from thermal or shock effects and is much harder to see but is sometimes visible by observing light from an external source being refracted at differing angles through the Schlieren mirrors and/or lenses are typically required to capture the effect reliably on camera The voltage waveform was recorded via a capacitive voltage divider with a ratio of 27,931:1 V and resolution in the volts range connected between the high voltage generator and electrode whereas the current was measured by a current transducer with a ratio of 0.1:1 A and resolution in the milliamps range positioned around the isolated earth lead connecting the ground plane to earth A pair of synchronised cameras designed to trigger at the same time as the application of the high voltage impulse were used to simultaneously capture the resulting streamers The cameras captured a series of still images at a rate of 21,000 fps resulting in each image lasting 47.62 µs with a timing error of 10.0 µs between them The first camera was positioned to observe directly the visible light emitted from the streamers whereas the second was positioned to observe the Schlieren effect through a specialised optical setup consisting of an LED point light source two 13 cm diameter biconvex lenses and a knife edge It is important to note that the images from the Schlieren camera are those of air density differentials with larger differentials being more prominent Experiments were carried out to observe both the visible light emissions and Schlieren structures of the resulting streamers The lens on the second camera was then adjusted and a second set of experiments were carried out to observe the development of the Schlieren structures over a longer period Schlieren structures were also observed during several electrical breakdowns All images were enhanced using post-processing image subtraction and brightening techniques Light emissions and Schlieren structures for positive and negative high voltage impulses applied to round flat and point electrodes opposite a ground plane All images are the first frame following the high voltage impulse which were all 0.4 kV below the experimentally determined breakdown voltages The images have been enhanced by image subtraction and 40% brightness increase for clarity The high voltage impulse profile, conforming to the BS60060-1 electrical standard17 (red) and the current profile exhibiting small spikes consistent with a relatively small flow of charge from ionisation of the air (green and zoomed area) Schlieren structures over time for a positive high voltage impulse applied to round, flat and point electrodes opposite a ground plane. The applied peak voltage impulse for each, which were all 0.4 kV below the experimentally determined breakdown voltages, are displayed above each image. The images have been enhanced by image subtraction and 40% brightness increase for clarity. Schlieren structures over time for a negative high voltage impulse applied to round Schlieren does exists but is only barely visible near the corners of the electrode the Schlieren structures were found to continue developing into the millisecond timeframe along filaments which connect between the previously energised electrode and the ground plane Data from the current transducer showed that there was no charge flow greater than the approximately 0.5 A noise level of the current transducer during this period indicating that if any charge were flowing then it would be very low not only along the filaments but also at both the high voltage electrode and ground plane This is reminiscent of the filaments seen in the light emission images presented in the previous section despite the light only being emitted in the first frame and the high voltage impulse having completely diminished by the fourth frame at 190.43 µs The Schlieren structures then expand in a perpendicular direction to their alignment whilst moving towards the centre of the air gap in a parallel direction eventually dissipating into the surrounding air over tens of milliseconds before disappearing completely within 100 ms the Schlieren structures can be considered a longer-lived imprint of the short-lived streamers within the air The perpendicular expansion of the filaments and movement of brighter regions towards the centre of the air gap of the Schlieren structures over time for round, flat and point electrodes, as measured from the data presented in Figs. 4 and 5 Schlieren structures over time for a positive high voltage impulse applied to round flat and point electrodes opposite a ground plane when an electrical breakdown has occurred The first images in each case are saturated These images have been enhanced by image subtraction and The electrode geometry has also affected the streamer formation as expected with the point electrode producing a smaller number of more direct streamer filaments and the flat and round geometries producing a larger spread of streamer filaments Proposed mechanism for the formation of positive and negative streamers between a pulsed high voltage electrode and ground plane across an air gap (a) Free electrons accelerated towards/away from the electrode creating ions (b) electrons accelerate and collide with more molecules creating an avalanche (c) recombination of ions and Bremsstrahlung radiation emitting light along forming filament structures the density change is maintained along the filaments creating a Schlieren imprint and (f) opposing regions of space charge move towards each other while the Schlieren imprint then diffuses into the surrounding air the results have demonstrated that light emissions and Schlieren structures coincide along the same streamer filaments with Schlieren more prominent around the electrode and ground plane where the field intensity is higher The high voltage impulse peaked at 50 μs and was fully dissipated by 300 μs whereas light was emitted only within approximately 100 μs The Schlieren continued to develop into the microsecond timeframe moving towards the centre of the air gap whilst diffusing into the surrounding air and fully dissipating within approximately 100 ms Such knowledge is important for the understanding and improved design of the insulation strength of insulation gaps subject to high voltage lightning impulse particularly using the longer-lived Schlieren imprint to understand streamer formation and where a failure or electrical breakdown of the insulation may occur this is important for the design and manufacture of gas insulated switchgear to better understand partial and full discharge events which can lead to rapid insulation failure result in widespread power distribution failures An illustration of the experimental setup The Schlieren system consists of the (a) bright LED light source (e) visible light camera and (h) a flat plane background The high voltage system consists of the (f) electrode and (l) oscilloscope for reading current and voltage An illustration of (a) the measurement of the movement of brighter regions near the electrode and ground plane towards the middle of the air gap and (b) the perpendicular expansion of the filaments The conductivity produced in gases by the motion of negatively charged ions In Advances in High Voltage Engineering (eds Haddad D.) (The Institute of Engineering and Technology The role of photoionization in positive streamer dynamics Role of photoionization processes in propagation of cathode-directed streamer Effects of photoionization on propagation and branching of positive and negative streamers in sprites Diagnostic techniques for is charges and plasmas In Electrical Breakdown and Discharge Gases NATO Advanced Science Institutes Series Vol Slow gas heating process in an atmospheric-pressure streamer discharge visualised by high-speed Schlieren method Thermal and hydrodynamic effects of nanosecond discharges in atmospheric pressure air Reconnection and merging of positive streamers in air Probing photo-ionisation: Experiments on positive streamers in pure gases and mixtures Stroboscopic images of streamers through air and over dielectric surfaces Widger, P., Hills, M. & Mitchard, D. Schlieren images of negative streamer and leader formations in CO2 and a CF3I-CO2 electronegative gas mixture. MDPI Appl. Sci. 10, 22. https://doi.org/10.3390/app10228006 (2020) The Physics of thundercloud and lightning discharge—Fundamental processes in long air gap discharges IEC 60060-1 High Voltage Test Techniques Part 1: General Definitions and Test Requirements (IEC Optical emission spectra of high current and high voltage generated arcs representing lightning Division of engineering: Engineering aspects of electro-gas-dynamics (Transaction of the New York Academy of Sciences Download references The authors gratefully acknowledge the financial support provided by the EU/Welsh Government funded project Advanced High Voltage Engineering Research Centre carried out the experiments and analysed the data wrote the manuscript with support from P.W Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41598-021-03839-y Credit: NurPhoto/Getty ImagesSwiss police say they had solved a kidnapping involving two dogs and a demand for ransom of a million Swiss francs Zurich police said that two Bolonka dogs were stolen from the home of a 59-year-old man in Schlieren near Zurich last week the dogs were gone and he found a letter demanding a million Swiss francs ($A1.806 million) to release the small dogs Get the first look at the digital newspaper curated daily stories and breaking headlines delivered to your inbox Get the NewsletterBy continuing you agree to our Terms and Privacy Policy.Instead of paying the ransom who was not identified by name in line with Swiss privacy rules police on Thursday arrested a 30-year-old Norwegian man at Zurich Airport who police said was strongly suspected of being involved in the theft Following further leads and cross-European co-operation police in Poland then detained a 38-year-old suspect and discovered the kidnapped Bolonkas which they returned safely to their owner on Friday Swiss police said the Norwegian man is in custody in Switzerland and authorities in Poland are further investigating the Polish suspect A Bolonka is a toy breed of dogs bred in Russia and sold for up to a couple of thousand dollars Latest EditionEdition Edition 5 May 20255 May 2025All-powerful Anthony Albanese says give me some R.E.S.P.E.C.T Metrics details Positive and negative fluorescent dichroic properties of dyes in NLC (a) Analyser-angle-dependence of relative fluorescence intensities of dye-doped NLCs in a planar cell with the thickness of 2 μm collected using the fluorescence microscopy setup The analyser at 0 degree is parallel to the director n without an electric field An AC electric field (peak-to-peak 10 V at 100 Hz) is applied in the surface normal direction to orient n perpendicularly The relative fluorescence intensities are values normalized by those at the angle of ±90 degree without electric field Schematics of the average configurations of transition dipole moments t of pyrromethene 597 (PMN) (shown by green colour) aligns along n indicating that PMN in NLC has positive dichroic property t of C-Naphox (CNX) (shown by red colour) is distributed perpendicularly to n with rotational freedom in the plane normal to n indicating that CNX has negative dichroic property Four regions with different cell thickness showing typical schlieren textures. Schlieren textures at the approximate thickness d of (a) 1, (b) 2, (c) 3, and (d) 4 μm. The colours arise from the interference due to the thickness dependent retardation of the NLC (5CB) with planar alignment. (Bar: 20 μm) (e) Number densities of defects with half integer and integer m at different thicknesses. and larger dark spots with CW vortex (L,CW) This result indicates that the pair (S,CCW) and (L,CW) is associated with one handedness of chirality and the other pair (S,CW) and (L,CCW) with the other handedness Confocal laser scanning (CLS) FOM images Images (10 × 10 μm2 squares) of systems with (a) PMN and (b) CNX at d ~2 μm transmittance image with crossed-nicols-like configuration and the schematics of the 2D n distribution Arrows with “P” indicate the polarizing direction of the incident laser and that with “A” indicates the polarising direction of the analyser The defect centres appear as dark for a system with PMN and bright for that with CNX Let us discuss the origin of the four different states found for defects with m =  +1. We first recall that the escape direction can be either upward or downward as shown in Fig. 1c and that the configurations with different escape directions are of the same free energy because the two confining substrates are equivalent and that with left-handed twist distortions can emerge with equal probability because of the inversion symmetry of the free energy and the boundary conditions The calculated rays entering from different points near the defect centre at the bottom side of the cell with different incident angles are shown for both up/down-states in Fig. 8c,d the incident rays clearly tend to deviate more from the defect centre for the down-state we discuss qualitatively how the bending of rays modulates 2D distributions of the excitation intensity and distort the resulting fluorescence images in which the elongated direction should correspond to the up-axis We adopted a wedge cell with planar alignment without preferential direction (degenerate planar alignment) to observe very thin regions at the thickness of roughly 1 to 4 μm Mikasa) was used at 5,000 rpm for 60 s to coat cover glass slides with a poly-amic acid solution (1 wt%) The coated slides were then heated on a hot plate at 70 °C for 2 min to evaporate the solvent and subsequently placed in an oven at 180 °C for 3 h to induce the transformation of poly(amic acid) to polyimide through the dehydration reaction two slides were assembled to a wedge cell using a Kapton® spacer placed at one side of the cell with a small amount of adhesive (liquid gasket1212 The slides were held together using clips during curing of the adhesive Although the wedge angle was ideally ~0.036 degree the actual cell showed spatial fluctuation of the wedge angle (and the cell gap) probably due to the bending of the cover glass and inhomogeneity in the thickness of the polyimide layer doped with 0.01 wt% PMN or 0.05 wt% CNX was injected into the wedge cell at an elevated temperature (40~45 °C) via capillary action The sample was cooled to room temperature (22 ± 2 °C) and used for microscopic observations which gives the cholesteric pitch much larger than d were prepared employing the same procedure For measurements of fluorescence dichroic properties a planar cell with unidirectional planar alignment (KSRP-02/A111P1NSS05 EHC; cell gap of 2 ± 0.5 μm) filled with 5CB doped with dyes was used We observed the LC alignment using a transmitted polarizing optical microscope (POM) (BX-51P we used a conventional fluorescence optical microscope (FOM) where the light source was mounted above the sample and the excitation light passed through the microscope objective lens on its way toward the sample A Xe lamp (75 W) was used as the light source we used a fluorescence filter set (U-MWIB-3 Olympus) comprising an excitation filter that transmitted light with wavelengths between 460 nm and 495 nm and an emission filter that transmitted light with wavelength larger than 510 nm The images were collected at the pixel size of 0.154 μm using a Nikon DS-Qi1-Mc CCD (charge-coupled device) camera connected to a computer and controlled through imaging software (NIS-Elements An objective lens with a numerical aperture (NA) of 0.95 (UPLSAPO40 × 2 For the measurements of dichroic properties the fluorescence intensity was measured using the FOM with a polarizer (analyser) through which the emitted fluorescence passed The average intensities were measured at different angles between the axis of the polarizer and the nematic director of the cell When the maximum and minimum intensities were at Φ = 0 degree and ±90 degree and the dye had positive dichroic fluorescence property When the intensity variation behaves in an opposite manner and the dye had negative dichroic fluorescence property To further confirm the alignment of dyes in 5CB the same measurements were conducted under the AC voltage to align n along the optical axis A confocal laser scanning (CLS) FOM (A1+ system Nikon) was used to obtain the fluorescence images of defects with integer m An optically pumped semiconductor laser (LU-N4 Laser Unit Coherent Inc.) was used to excite the fluorescent molecules at 488 nm and the emitted light between 525 and 595 nm was collected An objective lens with an NA of 1.45 (PlanApoTIRF60 × The CLS-FOM images were acquired at the pixel size of typically 60(x) × 60(y) nm2 The excitation laser was linearly polarized in y direction and all emitted fluorescence was collected The initial profile with an “escape” for m = +1 was set to be uniform along the z direction and taken to be \({Q}_{ij}(x,y,z)={Q}_{{\rm{i}}{\rm{n}}{\rm{i}}{\rm{t}}}({n}_{i}(x,y){n}_{j}(x,y)-(1/3){\delta }_{ij})\) where the director n(x,y) was set to the following: The initial profile for m = −1 is the same as that for m = +1 with n being flipped about the x axis locally We performed another calculation with chiral perturbations introduced in the above-mentioned initial profile for m = −1 and these perturbations turned out to decay resulting in an achiral profile mentioned in the main text According to Fermat’s principle, the path of extraordinary light from point A to B minimises the following integral5: Nematic and cholesteric liquid crystals (Taylor & Francis Elastic energies and director fields in liquid crystal droplets Colloids and Soft Materials: An Introduction to Soft Matter Physics Nych, A., Fukuda, J., Ognysta, U., Žumer, S. & Muševič, I. Spontaneous formation and dynamics of half-skyrmions in a chiral liquid-crystal film., Nat. Phys. https://doi.org/10.1038/nphys4245 (2017) Download references were supported by a grant for promotion of cooperation between Nagoya University and AIST were also supported by Grants for Fusion Emergent Research from Integrated Research Consortium on Chemical Sciences was supported by JSPS KAKENHI Grant Number JP17H02947 was supported by JSPS KAKENHI Grant Numbers JP17H06417 and JP17H06413 Research Institute for Sustainable Chemistry National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1 Higashi Institute of Transformative Bio-Molecules (ITbM) and Integrated Research Consortium on Chemical Sciences (IRCCS) performed the experiments and analysed the results arranged CLS-FOM and performed observations using CLS-FOM The authors declare that they have no competing interests Download citation DOI: https://doi.org/10.1038/s41598-017-16967-1 We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings. SearchBrowseServicesOpen researchInstitution LoginSearchMenu links This study identifies two previously unrecognised screech modes in non-axisymmetric jets Spectral proper orthogonal decomposition (SPOD) of ultra-high-speed schlieren images reveals a bi-axial flapping mode in a rectangular jet and a quasi-helical mode in an elliptical jet To educe the complex three-dimensional structure of these new modes SPOD is performed on datasets from different viewing perspectives produced by rotating the nozzle with respect to the schlieren path to an azimuthal angle $\theta$ The bi-axial flapping mode is strongly antisymmetric from any perspective the SPOD eigenvalue at the screech frequency ($\lambda _s$) varies with $\theta$ and the axial distance of the SPOD domain from the nozzle lip This mode most closely resembles a flapping mode in the minor-axis plane close to the nozzle lip and a wagging mode in the major-axis plane further downstream This transition from flapping to wagging at the same frequency correlates with the axis switching defined by the shock-cell structure in the mean flow The quasi-helical mode in the elliptical jet is characterised by an antisymmetric structure present in the SPOD spatial modes whose eigenvalue $\lambda _s$ is insensitive to both $\theta$ and the axial domain These findings indicate that the spatial evolution of the mean flow in non-axisymmetric jets may allow them to support a range of additional screech modes that differ significantly from those supported by the original three-dimensional shape of the jet the focus of this paper is on unusual manifestations of jet screech in non-axisymmetric jets The core of the weakest-link model is that the wavenumber of the upstream-propagating wave is selected via a triadic interaction between the Kelvin–Helmholtz (KH) wavepackets and the shock structures It has been shown that the discrete jump in frequency often (but not always) coincides with a modification in the azimuthal structure of the screech mode Screech modes have historically been denoted classified according to their azimuthal structure toroidal ($\mathrm {A1}$ and $\mathrm {A2}$) flapping ($\mathrm {B}$ and $\mathrm {D}$) and helical ($\mathrm {C}$) disturbances These modes can be linked to the natural instability of the jet which can be decomposed on an azimuthal basis into modes categorised by their azimuthal wavenumber $\mathrm {A1}$ and $\mathrm {A2}$ have been found to be linked to the ${m}=0$ mode The helical $\mathrm {C}$ mode is associated with the ${m}=\pm 1$ mode The $\mathrm {B}$ and $\mathrm {D}$ flapping modes are considered a special case of the ${m}=\pm 1$ modes where two helical modes happen simultaneously with a consistent phase relationship double-flapping diagonally ($\mathrm {ce}_2$) and double-flapping sidewards ($\mathrm {se}_2$) modes The $\mathrm {ce}_0$ corresponds to the toroidal ${m}=0$ mode in the axisymmetric jet case becoming identical in the limit as the aspect ratio approaches 1 The $\mathrm {se}_1$ and $\mathrm {ce}_1$ are likewise equivalent to the $|m|=1$ modes in the limit of $\mathrm {AR}=1$ but more closely resemble the flapping $\mathrm {B}$ and $\mathrm {D}$ screech modes away from this limit there is no preferred axis for the flapping mode the $\mathrm {se}_1$ and $\mathrm {ce}_1$ modes are locked to their particular axes and no further evidence of this ‘helical’ mode has appeared in the literature characterisation of this mode has remained underexplored (a) Schematic of the supersonic-jet experimental facility (b) Rectangular-nozzle geometry and global coordinate system Minor-axis and major-axis planes are marked by $\theta =0^\circ$ and $\theta =90^\circ$ $y^*=y$ when $\theta =0^\circ$ and $y^*=z$ when $\theta =90^\circ$ consider $\boldsymbol {q}_i = \boldsymbol {q}(t_i)$ as the mean-subtracted snapshots the dataset is segmented into $n_{{blk}}$ overlapping blocks Adjacent blocks overlap by $n_{{ovlp}}$ snapshots with $n_{{ovlp}} = n_{{fft}}/2$ for the present case ($50\,\%$ overlap) Each of the $n_{{blk}}$ blocks undergoes a Fourier transform in time and all Fourier realisations at the $l$th frequency are organised into a matrix $\widehat {\boldsymbol {Q}_l} = [\hat {\boldsymbol {q}}^{(1)}_l \hat {\boldsymbol {q}}^{(2)}_l,\ldots,\,\hat {\boldsymbol {q}}^{(n_{{blk}})}_l]$ The SPOD eigenvalues $\boldsymbol {\varLambda }_l$ are determined by solving the eigenvalue problem $({1}/{n_{{blk}}}) \hat {\boldsymbol {Q}}_l^* \boldsymbol {W} \hat {\boldsymbol {Q}}_l \boldsymbol {\varPsi }_l = \boldsymbol {\varPsi }_l \boldsymbol {\varLambda }_l$ where $\boldsymbol {W}$ is a positive-definite Hermitian matrix accounting for the component-wise and numerical quadrature weights and $( {\cdot } )^*$ indicates the complex conjugate The SPOD modes for the $l$th frequency are then obtained as $\boldsymbol {\varPhi }_l = ({1}/{\sqrt {n_{{blk}}}}) \hat {\boldsymbol {Q}}_l \boldsymbol {\varPsi }_l \boldsymbol {\varLambda }_l^{-1/2}$ The eigenvalues $\boldsymbol {\varLambda }_l = \text {diag}(\lambda _l^{(1)} \lambda _l^{(n_{{blk}})})$ represent the energies of the corresponding SPOD modes with $\lambda _l^{(1)} \geq \lambda _l^{(2)} \geq \cdots \geq \lambda _l^{(n_{{blk}})}$ denoted by the columns of the matrix $\boldsymbol {\varPhi }_l = [\boldsymbol {\phi }_l^{(1)} represent the coherent structures in the flow at the $l$th frequency with $\boldsymbol {\phi }_l^{(j)}$ being the $j$th mode The spectral-estimation parameters used here are $n_{{fft}}=4096$ and $n_{{ovlp}}=2048$ resulting in $n_{{blk}}=47$ SPOD modes for each frequency The dataset used herein has $n_t=100\,000$ snapshots The SPOD-eigenvalue spectra of the leading mode for the rectangular jet viewed in the minor-axis plane ($\theta =0^\circ$) at: (a) $\mathrm {NPR}=2.0$; (b) $\mathrm {NPR}=2.6$; (c) $\mathrm {NPR}=4.0$ $St_s$ and $\lambda _s$ indicate the screech frequency and associated SPOD eigenvalue only the initial and final pressures at which the peaks appear in the SPOD-eigenvalue spectra are marked Rectangular jet in varicose mode at $St_s=0.92$ and $\mathrm {NPR}=2.0$ (i–l) Schematic of the viewing perspective (a) Cross-correlation coefficient $\beta$ between symmetric planes around the $z$-axis for a rectangular jet at $\mathrm {NPR}=2.0$ (b) Angular dependence of the SPOD eigenvalue at the screech frequency for both rectangular and elliptical jets in the varicose mode the corrected $\lambda _s$ is found to be relatively constant for different $\theta$ indicating that the fundamental screech frequency is dominant in all axes Rectangular jet in flapping mode at $St_s=0.39$ and $\mathrm {NPR}=2.6$ (a) Cross-correlation coefficient $\beta$ between symmetric planes around the $z$-axis for a rectangular jet at $\mathrm {NPR}=2.6$ (b) Angular dependence of the SPOD eigenvalue at the screech frequency for both rectangular and elliptical jets in the flapping mode Rectangular jet in bi-axial flapping mode at $St_s=0.27$ and $\mathrm {NPR}=4.0$ Time-averaged shock structures for the rectangular jet at $\mathrm {NPR}=4.0$ when viewed in (a) the minor-axis plane and (b) the major-axis plane (c) Comparison of spanwise size of the shock-cell structures; shock cells are marked by cyan and magenta solid lines in the minor-axis plane and major-axis plane Rectangular jet exhibiting bi-axial mode at $St_s=0.27$ and $\mathrm {NPR}=4.0$ (a) Angular dependence of $\lambda _s$ for various subdomains (b) Cross-correlation coefficient $\beta$ between symmetric planes around the $z$-axis Rectangular jet exhibiting flapping mode at $St_s=0.23$ and $\mathrm {NPR}=4.0$ Rectangular jet exhibiting varicose mode at $St_s=0.30$ and $\mathrm {NPR}=4.0$ (b) Cross-correlation coefficient $\beta$ between symmetric planes around $z$-axis Elliptical jet in the quasi-helical mode at $St_s=0.28$ and $\mathrm {NPR}=3.6$ Time-averaged shock structures for the elliptical jet at $\mathrm {NPR}=3.6$ when viewed in (a) the minor-axis plane and (b) the major-axis plane Elliptical jet exhibiting quasi-helical mode at $St_s=0.28$ and $\mathrm {NPR}=3.6$ Elliptical jet exhibiting flapping mode at $St_s=0.32$ and $\mathrm {NPR}=3.6$ (i–j) Schematic of the viewing perspective The features of two previously unrecognised screech modes in non-axisymmetric jets have been identified for the first time in this study By analysing ultra-high-speed schlieren images using spectral proper orthogonal decomposition (SPOD) a bi-axial flapping mode in a rectangular jet and a quasi-helical mode in an elliptical jet have been discovered schlieren measurements have been taken from different azimuthal angles ($\theta$) to reconstruct 3-D flow structures of the supersonic jet The bi-axial flapping mode is found to be strongly antisymmetric about the $x$-axis when viewed from any perspective but the SPOD eigenvalue at the screech frequency ($\lambda _s$) is found to vary depending on $\theta$ and the axial distance of the SPOD domain from the nozzle lip $\lambda _s$ decreases gradually as the viewing perspective is varied from the minor-axis plane ($\theta =0^\circ$) to the major-axis plane ($\theta =90^\circ$) This dependence on angle indicates a flapping mode in the minor-axis plane for a SPOD domain defined further downstream a gradual increase in $\lambda _s$ from $\theta =0^\circ$ to $\theta =90^\circ$ indicates that in this region the jet is ‘wagging’ in the major-axis plane this suggests that the screech mode experiences a transition from a flapping mode to a wagging mode at the same frequency It is demonstrated that the location at which this switch takes place correlates with the location of axis switching as defined by a consideration of the shock-cell structure in the mean flow The quasi-helical mode in the elliptical jet is examined through the same methodology Distinct from the bi-axial mode in the rectangular jet this mode is characterised by the antisymmetric structure in the SPOD spatial modes with an eigenvalue $\lambda _s$ that remains unaffected by both $\theta$ and the axial domain The discovery of these new structures indicates that in addition to the commonly known screech modes supported by the original 3-D shape of the jet the axial variation in the mean flow in non-axisymmetric jets could support a variety of additional screech modes This work was supported by the Australian Research Council through the Discovery Project scheme: DP220103873 The authors report no conflict of interest Convergence of the SPOD spatial modes for elliptical jet operating at $\mathrm {NPR}=3.6$ and (a) $St_s=0.28$ (b) $St_s=0.32$ Convergence of the SPOD eigenvalue $\lambda _s$ for elliptical jet operating at $\mathrm {NPR}=3.6$ and (a) $St_s=0.28$ (b) $St_s=0.32$ Frequency spectra as a function of nozzle pressure ratio for (a) elliptical jet $\mathrm {AR}=2.0$; (b) rectangular jet $\mathrm {AR}=2.0$ The cyan triangles (cyan $\triangle$) denote the first peak in the varicose mode cyan squares (cyan $\square$) and cyan plus signs (cyan $+$) represent the first (the lowest $St_s$) second (the middle $St_s$) and third (the highest $St_s$) peaks identified in the SPOD-eigenvalue spectra shown in figure 2(c) - No HTML tags allowed- Web page URLs will display as text only- Lines and paragraphs break automatically- Attachments Your email address will be used in order to notify you when your comment has been reviewed by the moderator and in case the author(s) of the article or the moderator need to contact you directly shared ownership in or any close relationship with any organisation whose interests may be affected by the publication of the response Please also list any non-financial associations or interests (personal religious or other) that a reasonable reader would want to know about in relation to the submitted work This pertains to all the authors of the piece The airborne spread of pathogens has assumed great importance in the public eye following the onset of the coronavirus disease 2019 (COVID-19 pandemic). In an interesting new research paper published recently on the bioRxiv* preprint server scientists describe the dispersal of exhaled air from singers and those playing wind instruments a visual process that is used to photograph the flow of fluids of varying density This could help assess measures to assess the actual spread of infectious droplets or aerosols in such situations It is now known that both droplets and aerosols with a size of > 5 µm and < 5 µm carry the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can spread outwards depending on their size travel only a few seconds before they fall to the ground the smaller particles in aerosols can remain suspended far longer in the air several studies have concluded that the spread of such particles is almost nil at 0.5 m from the mouth of a professional singer as indicated by the presence of only minute disturbances observed at a candle flame placed at this distance from the source of exhaled air it was observed that exhalation of air is much more forcible during professional singing rather than during speaking or breathing the pattern of air escape is similar to that of singing with the distance of spread being determined by the speed at which air escapes from the mouth or instrument and the outlet diameter The current study applies flow visualization techniques and anemometry to investigate the dispersal of exhaled air in terms of the pattern of spread and the velocity at which the air escapes The scientists used two methods to observe the flow schlieren imaging using a schlieren mirror and background-oriented schlieren (BOS) Schlieren refers to a method of photography applied to the visualization of flows of varying density by exploiting the bending or refraction of light rays when they pass across an interface separating two substances of different densities The advantages of these techniques are the ability to observe density gradients in transparent media due to variations in temperature or pressure The measurement field of schlieren imaging is restricted by the mirror size To correctly visualize the spread of exhaled air beyond these limits The breathing air is warmer and more humid than the surrounding air leading to gradients that can be captured by these techniques The researchers looked at woodwind instruments which release air in an initial laminar pattern followed by turbulence and finally mixing with the surrounding room air the air spreads most as the tone production begins and is highest when singing consonants or when precise articulation is required The researchers observe that both the distance to which exhaled air spreads and the angle at which air escapes are both different with the instrument and player and is blown over (flutes) or leaks near the mouthpiece (with the oboe or bassoon) Playing the oboe or bassoon requires intermittent exhalation through the mouth and nose as well since all the air cannot escape from the tone holes The air travels fastest when high pitches are used the velocity decreases steadily thereafter accounting for air movements of about 0.02 m/s at 85 cm away from the bell the highest velocity is observed at 45 seconds corresponding to very transient jets produced by large emissions of breathing air Air escapes from the bell over much shorter distances relative to the air that leaks from the instrument at various points Air leaks can travel about 60 cm into the room from the intermittent exhalation of air through the mouth and nose between two phrases it moves to within 30 cm when playing various notes while the greatest velocity of airflow from the bell is at low notes Since most tone holes are uncovered at high notes these produce maximal airflow from these holes The air escaping from the bell travels different distances depending on the bore width and the breathing pressure at the moment of playing the schlieren imaging shows that with most of these instruments the escaping air from the bell is very turbulent because of the bigger diameter of the bell The air blown into the mouthpiece blows into the bell The breathing air either travels up because of natural convection or mingles with the room air The factors that decide the shape and the distance of the air that escapes from the bell include the musician’s physique and blowing technique and the angle of the instrument to the mouth Breathing air goes out from the bell to about 25 cm at low pitches and a little more at high pitches Air can leak from the mouthpiece when the player’s lips become tired or when the musicians are untrained or older the escape of air is substantially reduced except with the F tuba and the French horn when a stopping mute is used Anemometry findings confirmed the results of the Schlieren visualizations showing that flow values are always above about 0.02 m/s The reasons might include finger or hand movements during playing or other convection airflows in the same room the measured velocity first decreases as the distance from the instrument increases and then begins to increase producing small vortexes that result in varying velocity To reduce such flow from all kinds of brass instruments the researchers said a simple filter could be used This will work because the air that is breathed through such instruments escapes entirely through the bell air escapes from the tone holes and even leaks from the mouthpiece A filter will not hinder the spread of the air This data could help discover the range to which exhaled air potentially containing infectious particles could spread during infectious airborne disease outbreaks the studies only show the range of larger droplets' spread since small droplets or aerosols are not visualized by Schlieren methods These results show that airflow does not travel more than 1.2 m into the room these patterns relate to air blown out by professionally trained singers and musicians Amateurs and learners may produce very different exhalation patterns and leakage which may result in a larger volume of air spread into the room The movement of the player can also change the velocity of the breathing air which also varies with the bell diameter and the breathing pressure Air escaping from the mouth or leaking at the mouthpiece shows a higher velocity of up to 0.15 m/s and velocity at which it escapes and spreads can be estimated for woodwind and brass instruments and professional singers This would help quantify the risk of viral transmission during such performances so as to develop the best safety precautions for such situations Posted in: Medical Science News | Medical Research News | Disease/Infection News who graduated from the Government Medical College Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility and has been in charge of over 2,000 deliveries striving always to achieve a normal delivery rather than operative Please use one of the following formats to cite this article in your essay Schlieren techniques demonstrate patterns of exhaled air spread from wind instruments and singers 2025 from https://www.news-medical.net/news/20210110/Schlieren-techniques-demonstrate-patterns-of-exhaled-air-spread-from-wind-instruments-and-singers.aspx "Schlieren techniques demonstrate patterns of exhaled air spread from wind instruments and singers" <https://www.news-medical.net/news/20210110/Schlieren-techniques-demonstrate-patterns-of-exhaled-air-spread-from-wind-instruments-and-singers.aspx> https://www.news-medical.net/news/20210110/Schlieren-techniques-demonstrate-patterns-of-exhaled-air-spread-from-wind-instruments-and-singers.aspx Cancel reply to comment Learn how experts are advancing benzodiazepine analysis and detection using insights from the lab discusses how he is addressing today’s medical challenges using the technology of the future Explore how the Radian ASAP mass spectrometer is being used to streamline and enhance seized drug screening you can trust me to find commercial scientific answers from News-Medical.net please log into your AZoProfile account first Registered members can chat with Azthena, request quotations, download pdf's, brochures and subscribe to our related newsletter content A few things you need to know before we start Read the full Terms & Conditions In a public-outreach effort earlier this year NIST scientist Matthew Staymates used schlieren photography to qualitatively show the difference in how far a plume of breath can spread with and without a face covering The COVID-19 pandemic has mobilized and focused the scientific community as never before with researchers hard at work toward vaccines and treatments and seeking other ways to press technology into service in slowing the spread of the disease Not all of the techniques capable of making a contribution are necessarily new or “cutting edge.” One example is schlieren photography an optical approach to visualizing airflows that was first developed more than a century and a half ago schlieren photography is a workhorse in aeronautical engineering—where it is used to image airflows in wind tunnels for example—as well as in a variety of other niche areas such as detection of drugs and explosives The technique works by detecting variations in the refractive index in a moving fluid due to temperature and density gradients is shone into a spherical concave mirror with a long focal length The test subject is positioned in front of the mirror and light bouncing off of the mirror and passing through the test area is returned to a camera positioned somewhat behind the mirror’s focal point a thin barrier—typically a knife edge or razor blade—is carefully placed so that it blocks out a portion the changes in temperature and density caused by the moving fluid locally shift the refractive index bending the light so that it is blocked by the knife edge The light that finds its way to the camera thus shows a pattern of light and dark patches And when those images are captured with a high-speed camera and stitched together into video they can provide compelling qualitative visualizations of just what happens when we exhale or cough The use of schlieren photography to image exhaled human airflows isn’t a brand-new idea researchers led by Gary Settles of Penn State University and Julian Tang of the National University Hospital used the technique in a variety of academic studies that offered insights on the dynamics of human coughs the technique’s strengths in visualizing the otherwise invisible have taken on new relevance—both in the scholarly quest to understand the mechanisms of virus transmission and in the effort to persuade the public of the importance of measures such as social distancing and face coverings to stem the disease’s spread One scientist who has been active in using schlieren imaging on the public-outreach side is Matthew Staymates an experimental fluid dynamicist at the U.S National Institute of Standards and Technology (NIST) who trained under Gary Settles at Penn State typically has used schlieren photography as a technique for detecting drugs and explosives “that schlieren is a really powerful tool to try to understand how to sample for these kinds of things in the environment.” as public controversy grew about the role and importance of wearing face coverings to stem the spread of the virus—Staymates realized that schlieren photography could offer a way to raise public awareness of the importance of face coverings and the visuals are quite striking,” he says and they’re fairly easy for the average person to understand.” Separated from his lab by coronavirus stay-at-home orders He obtained permission from NIST to bring some of his lab gear home—which was “a real gift,” he says and the idea of being stuck at home ‘teleworking,’ as a professional scientist was really starting to stress me out.” In addition to being a lab nerd, Staymates is also an avid woodworker—and, drawing on these talents, he converted his basement shop into a schlieren imaging lab, which he used to visualize airflows when he exhaled or coughed, both without a mask and with different kinds of face coverings. (He documented his efforts in a popular blog post on the NIST site.) NIST’s Matthew Staymates used schlieren photography to create a video showing airflow patterns from exhaled breath and coughing in an effort to raise public awareness of the role of masks in preventing the pandemic’s spread The result of these efforts was a viral online video that graphically showed the difference made by wearing face coverings—and that spurred a huge reaction “A lot of people wrote to me personally,” Staymates reports thank you so much—my family was so against masks and I showed them this and now they understand.’” He says he’s also heard from other federal organizations with offers to collaborate which want to post the videos at their building entrances to underscore to patrons the importance of keeping their faces covered during their visits The experience also has Staymates exploring new research possibilities for his schlieren setup “We’ve found kind of a new application space for schlieren that we weren't really tapped into before,” he says “There are a lot of really cool things happening.” “Schlieren is good at helping us understand airflows,” he warns “but we can’t make any claims about droplet mitigation using schlieren … We’re looking at airflows and refractive-index changes; we’re not looking at droplets and virus transport.” He stresses that it’s “critical to do that messaging or the untrained eye could draw the wrong conclusions.” A research team in India uses schlieren imaging to compare outflow patterns with varying degrees of face covering—and to uncover quantitative insights on the fluid dynamics of human coughs and breathing. [Image: Padmanabha Prasanna Simha, Indian Space Research Organisation] [Enlarge image] Meanwhile, other research groups are also leveraging schlieren imaging in an effort to better understand how to manage human airflows and contagion in the COVID-19 era. In a paper published today in Physics of Fluids two Indian researchers—Padmanabha Prasanna Simha an aeronautical engineer at the Indian Space Research Center a physician with the Sri Jayadeva Institute of Cardiovascular Sciences and Research—shed further light on the efficacy of face coverings and on the detailed fluid dynamics of human coughing The research team came together naturally in this case; Mohan Rao and Prasanna Simha are father and son “There’s been so much controversy on masks—people saying you should wear them they don’t work” says Mohan Rao Drawing on his experience in the aeronautical lab Prasanna Simha set up a schlieren system to do just that 3-m-focal length mirror taken from “a small wind tunnel,” a 250-W tungsten halogen lamp with a condenser lens to approximate a point source They captured images from the setup using a high-speed Phantom v641 camera running at speeds ranging from 100 to 5000 frames per second the pair set to work on imaging a variety of coughing scenarios One objective was to obtain a more quantitative understanding of how the airflows from human exhalation or coughing behave over long distances “Most previous research using schlieren imaging on human exhaled airflows has been qualitative,” notes Prasanna Simha And they’ve been “typically close to the mouth and nose so you don’t really get an estimate of how far the exhaled airflow is going.” In addition to studying airflows over long distances the team also looked at a variety of common face-covering scenarios in addition to coverings such as N95 protective masks and medical masks other common-sense approaches such as covering one’s mouth with one’s hands The latter approach—often recommended to prevent disease spread—turned out to be particularly problematic if the arm is not covered by a shirtsleeve “the flow tends to bend along the elbow and goes along in that direction,” says Prasanna Simha “If you were angry with someone,” laughs Mohan Rao “you could direct your cough at them this way.” Prasanna Simha and Mohan Rao believe that their work underscores the value of masks in potentially stemming the spread of COVID-19 And their quantitative use of the schlieren technique underscores a potentially unappreciated point they say: The efficacy of masks stems not only from their ability to filter droplets but from their effects on reducing airflow velocity—and thus distance of spread “It’s not just about the filtration efficiency,” says Prasanna Simha “If you can reduce the distance of propagation then even if you don’t have the best filtration efficiency the mask is still effective in terms of reducing the spread of infection.” One way the team was able to establish this was by looking at cough dispersion over longer distances our field of view is restricted to the size of the mirror,” Prasanna Simha notes “So the simple solution is to move [the test subject] out of the field of view and wait for the cough to move into the field of view but it hadn’t been tried before to quantify the spreading distance of coughs.” The work by Prasanna Simha and Mohan Rao also casts some light on the detailed fluid dynamics of a typical human cough—findings that could have their own role in better understanding how to stem human-to-human transport of the disease Through visual analysis of the schlieren images and by fitting the velocity–distance relationships gleaned from the images to a known analytical relation for viscous flow the team was able to establish that the airflows from the coughs follow the physics of so-called viscous vortex rings This could be important for future research “Computational studies have shown that vortex rings are able to enhance the transport of particles,” he explains “The rotational motion of the vortex is able to offset some of [the downward tendency due to gravity] and enhance particle transport … So if you had a mask that can attenuate the strength of the vortex ring right at the beginning it will play a huge role in minimizing the effect of distant transport.” that future tests using typical tools such as mannequins and cough simulators will need to “recreate similar [vortex] flow fields in order to accurately capture the propagation of airflow from coughs.” Wafer‑Scale Switch Promises a Photonic Fast Lane for AI A New Color Comes into View Optical Vortices 2020) ­– Keeping musicians safe while they're on stage during the pandemic may require more than just social distancing according to a study of exhaled aerosols conducted by Rice University engineers and musicians from Rice's Shepherd School of Music and the Houston Symphony Rice researchers working on the study used a high-speed camera to track the movements of exhaled air released by singers and musicians who play wind instruments "Social distancing is an important part of minimizing pandemic-related risks but our study points to the importance of other factors as well," said Ashok Veeraraghavan a Rice imaging expert involved in the study "Our main message is that there is no single silver bullet Performance venues are going to need a mix of several different risk mitigation strategies and the sum total of all of them will minimize risk to both the performers and the audience." With musical organizations around the world making plans for fall performances, the researchers opted to publish their data "People are making decisions about how to return to the stage and an important goal of this project was to provide guidance for them as quickly as possible," said Robert Yekovich dean of the Shepherd School of Music and co-principal investigator of the study and we believe it is imperative to make others aware of what we found." The COVID-19 pandemic brought traditional orchestra and opera performances to an abrupt halt in the spring With tens of thousands of professional musicians sidelined the overriding question was whether orchestral and opera performances could be modified to continue during the pandemic Using schlieren imaging a decades-old technique for filming airflow Veeraraghavan's team filmed a female and male singer as well as performers playing the flute Three members of Veeraraghavan's research group postdoctoral researcher Vivek Boominathan '19 and graduate students Ankit Raghuram and Sean Farrell conducted the experiments in a large rehearsal hall at the Shepherd School in late August a specially printed high-resolution background and computational algorithms Veeraraghavan's team was able to visualize the direction and flow of exhaled air coming from the musicians' instruments and mouths Veeraraghavan said existing social distancing guidelines and recommendations largely stem from well-documented studies on relatively large droplets of exhaled fluid that fall to the ground within a few feet Rice's experiments were designed to capture information about exhaled aerosols tiny microdroplets of fluid that may behave in a fundamentally different way from large droplets Aerosols can linger in the air for minutes or hours and are an important factor in the spread of airborne diseases. Mounting evidence suggests the coronavirus that causes COVID-19 can spread through aerosols "Our hypothesis going into the study was that microdroplet spray in front of the singer and instruments was the thing we needed to pay the most attention to," Veeraraghavan said The experiments showed that much of the air exhaled by performers tended to rise toward the ceiling and join air currents created by the room's air-conditioning vents "Airflow disturbance was concentrated around subjects' mouths and the holes in their instruments," he said "Because exhaled air was warmer than the room air carrying the bulk of exhaled microdroplets into air currents that were primarily driven by ventilation." Veeraraghavan said the authors recommend music venues ensure ventilation systems meet or exceed federal guidelines of six room air exchanges per hour "More is clearly better in terms of risk mitigation," he said The researchers also suggest venues examine the direction of air currents and consider ways to capture and filter air above the stage "Outflow vents above the performance stage will help but there may be other ways to engineer solutions," Veeraraghavan said "Our study clearly shows that ventilation is important The next step is to work with ventilation experts to use this knowledge in designs that make spaces safer." Veeraraghavan said it is still vitally important to use social distancing to minimize the risk of spreading COVID-19 via large exhaled droplets He said music venues should require masks and apply standard social distancing guidelines of 6 feet between performers and audience members alike He said another area for creative solutions could be in designing masks that allow performers to play their instruments but block some air that might otherwise escape from the sides of their mouths The full study recommendations, analysis and data are available at tunesflow.rice.edu it looked like safety was primarily going to be a matter of distance between performers on stage and between performers and audience," said Mangum "The Rice experiments showed it's more complex than that Now we want all musical organizations and individual musicians to benefit from that understanding." https://tunesflow.rice.edu https://youtu.be/dVhl-CINMKs High-resolution IMAGES are available for download at: This release can be found online at news.rice.edu Follow Rice News and Media Relations via Twitter @RiceUNews Located on a 300-acre forested campus in Houston Rice University is consistently ranked among the nation’s top 20 universities by U.S Rice has highly respected schools of Architecture Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy With 3,978 undergraduates and 3,192 graduate students Rice’s undergraduate student-to-faculty ratio is just under 6-to-1 Its residential college system builds close-knit communities and lifelong friendships 1 for lots of race/class interaction and No 1 for quality of life by the Princeton Review Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance 713-348-0000 | Privacy Policy | Campus Carry The experimental setup for the new 3D imaging method includes a single high-speed camera two xenon lamps and a series of fiber bundles This equipment is all relatively affordable compared with the more complex and specialized setup used in other techniques Schlieren imaging is an optical technique capable of visualizing invisible flow structures heat rising off a human hand or a jet of warm air from a hair dryer Now, researchers in China say they have developed a high-speed 3D schlieren approach that can image fundamental turbulent flame properties during combustion (Opt. Lett., doi: 10.1364/OL.496333) The technique improves upon previous 3D schlieren methods by using only a single high-speed camera instead of multiple as well as boosting the temporal resolution Traditional schlieren imaging employs light from a single collimated source shining on or behind a target object Any spatial variations in density caused by factors like pressure or temperature lead to changes in the refractive index distorting the beam and resulting in a 2D image of fluid flow progress has been made in extending schlieren measurements to three dimensions Most approaches up to this point have required several cameras to capture flow information from different perspectives followed by tomographic reconstruction to create a 3D distribution of flow properties disadvantages to these methods include limited temporal and spatial resolutions difficulties in processing data and the high cost of equipment Qingchun Lei and his colleagues demonstrated a new 3D schlieren technique that combines fiber imaging traditional schlieren imaging and computed tomography (CT) which only includes a single high-speed camera they could simultaneously capture the schlieren images of turbulent flames from seven orientations with a frame rate beyond tens of kilohertz The complex behavior of the turbulent flames produced during combustion Shown on the left are two cross sections of the 3D density measurement; the horizontal slice is at Z = 16 mm and the vertical slice at X = 0 mm On the right is the 3D isosurface of the largest density gradient between the mixture and burned product It depicts turbulent wrinkles and flame pockets “The high-speed imaging approach we developed provides detailed insights into flame dynamics ignition processes and combustion behavior,” said study author Lei in a press release accompanying the research “This can provide insights into combustion efficiency pollutant emissions and the optimization of energy production processes that could be used to improve the design and operation of power plants leading to reduced environmental impact and enhanced energy efficiency.” The light source consisted of two xenon lamps two fan-out fiber bundles and seven collimating lenses The fiber bundles split the light into seven individual rays after which the lenses expanded and guided the light to pass through the flame area the imaging setup included seven convergent lenses seven knife edges to block some of the incoming light a bifurcate imaging fiber bundle and a CMOS high-speed camera the researchers used CT reconstruction and postprocessing to obtain 3D schlieren images along with 3D density and velocity information The system successfully measured both turbulent and stable laminar premixed flames at a lower cost and higher speed than previous methods “The detailed understanding of flame behavior and ignition processes facilitated by this technique can also contribute to more effective fire safety measures by providing information on how fires spread develop and can be suppressed,” said Lei “This can be used to enhance fire prevention strategies improve building designs and develop more efficient fire suppression systems that could ultimately help save lives protect property and improve overall fire safety standards.” An official website of the United States government https://www.nist.gov/programs-projects/aerodynamic-flow-visualization This effort uses advanced fluid flow visualization and flow diagnostic techniques to better-understand the role of fluid dynamics in our Safety & Security focus area Laser light sheet imaging is used to visualize the generation This is particularly useful for visualizing the spread of hazardous contamination during the manufacturing of improvised explosive devices and illegal drug mixtures along with visualizing gun shot residue plumes Schlieren imaging allows one to visualize air movement and is used to optimize vapor sampling and detection and helps demonstrate the fluid dynamics of canine olfaction Schlieren is also used for public health communication by studying human breathing and coughing These visualization techniques are coupled with high speed videography enabling high-resolution and high-frame rate imaging of rapid events such as air jet blasting (for non-contact sampling) rapid thermal desorption of contraband materials "Filter Inserts Impact Cloth Mask Performance against Nano- to Micro-Sized Particles" James G "Hydration of Hydrophilic Cloth Face Masks Enhances the Filtration of Nanoparticles" Christopher D "Flow visualization of an N95 respirator with and without an exhalation valve using schlieren imaging and light scattering" Matthew Staymates "Net weights: Visualizing and quantifying their contribution to drug background levels in forensic laboratories" Edward Sisco, Matthew E. Staymates, Laura M. Watt "An easy to implement approach for laboratories to visualize particle spread during the handling and analysis of drug evidence" Edward Sisco "Optimization of confined direct analysis in real time mass spectrometry (DART-MS)" Edward Sisco