Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session T25: Acoustics: General |
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Chair: Brian Elbing, Oklahoma State University-Stillwater Room: 251 C |
Monday, November 25, 2024 4:45PM - 4:58PM |
T25.00001: Advanced Ultrasound techniques and Machine learning algorithms for particle size distribution analyses Fria A Hossein, Panagiota Angeli Abstract: |
Monday, November 25, 2024 4:58PM - 5:11PM |
T25.00002: Effect of fluidic injections near the end of potential core for a Mach 0.5 subsonic jet Arnab Samanta, Ambica Singh, Arun K Perumal Although jets are known to be most receptive at the nozzle |
Monday, November 25, 2024 5:11PM - 5:24PM |
T25.00003: Preliminary Evidence of Sound Amplification of Turbulent Noise due to Latent Heat Garrett D Terry, Aaron S Alexander, Douglas Fox, REAL J KC, Brian R Elbing Infrasound is sound that is below the human threshold of hearing. It has been observed that tornadoes and tornadic storms produce infrasound signatures that relate to the characteristics and formation of the tornado. Detecting infrasound signatures from tornadic storms could be a new method for tornado detection, especially in areas with hilly terrain where line-of-sight methods such as radar are not as effective. However, to effectively use this method of detection, the physical mechanisms responsible for the infrasound signature must be determined. It has been theorized that a thermodynamic effect related to water condensation within the tornado is responsible for amplifying the infrasound signature. An experimental method to create this thermodynamic effect within a small turbulent jet has been developed. Microphones were positioned to measure the sound propagating from the turbulent jet. A comparative analysis of the sound pressure levels from a dry and saturated jet with and without external cooling was performed. This presentation will show the preliminary findings from the experimental setup that indicate that the theorized effect could be present. |
Monday, November 25, 2024 5:24PM - 5:37PM |
T25.00004: Ground Infrasound Observations from the OSIRIS-REx Sample Return Capsule Re-entry Brian R Elbing, Douglas Fox, Trevor C Wilson, REAL J KC, Kate B Spillman The OSIRIS-REx Sample Return Capsule (SRC) re-entered the Earth's atmosphere on the morning of 24 September 2023. The SRC entered the atmosphere over the Pacific Ocean at a speed of over 43,000 km/hr and a few minutes later landed in Utah. The hypersonic entry of the SRC produced a shockwave as it entered the denser regions of the atmosphere that then decayed to infrasound (i.e., sound at frequencies below human hearing). Our team had microbarometers deployed on the ground near the border between Nevada and Utah to detect these infrasound waves. Most of the sensors were deployed at Wendover Airport that was nominally 58 km to the north of the SRC trajectory. Two of the sensors were deployed between the SRC trajectory and the airport. Three different sensor models (Chaparral Physics, GEM, and WERD) were deployed in close proximity to compare their performance. All the sensors observed an N-wave arrival followed by broadband coherent rumbling after the initial arrival. This presentation will present details of the deployment as well as preliminary results including beamforming of the received signals. |
Monday, November 25, 2024 5:37PM - 5:50PM |
T25.00005: Time domain aeroacoustic source separation with statistical inversion Mitchell J Swann, Samuel J Grauer, Adam Nickels, Michael H Krane, Jeff Harris We present an application of statistical inversion for source separation of time domain microphone array signals observing an aeroacoustic source. Here, the acoustic emission of an individual vortex ring convecting past the edge a semi-infinite half-plane in an anechoic chamber is measured. Inherent to the production of individual vortex rings, a spherical shock wave is produced, polluting the acoustic measurement. The vortex/edge (V/E) interaction is observed by a circular 12-microphone array centered about the edge of the half-plane where the vortex interaction is significant. Synchronous high-speed Schlieren imaging captures the formation and convection of the individual vortex rings. Sources present in the experiment are non-stationary and impulsive, limiting the efficacy of frequency domain source separation methods, necessitating a time domain approach. A model approximating the microphone array signals is introduced, which is parameterized in terms of experimental setup and aeroacoustic source parameters. Statistical inversion of the approximating model enables the estimation of the underlying source waveform time series of the V/E interaction in addition to estimating its uncertainty. Finally, the estimated V/E source parameters are compared to prior results. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T25.00006: Microfiber coating for a blade-noise reduction Russell Henggeler, Mitsugu Hasegawa, Hirotaka Sakaue Microfiber coating has been proven as a drag reduction device for a blunt body. This study investigates the microfiber coating as a device for aeroacoustic noise reduction over a propeller blade in small aerial vehicles. The microfiber coating forms an array of hair-like surfaces that can be taped on a blade. To determine the optimal microfiber locations for a blade-noise reduction, the strips of microfiber coating are placed at different spanwise and chordwise locations on the blade. Sound level is captured to evaluate the aeroacoustic noise from the blade. Microfiber strips reduce the sound level compared to the baseline, which is a bare surface, with a more significant noise reduction effect at the trailing edge rather than the leading edge. The spanwise location of the microfiber coating is important to maximize noise reduction. The current progress of this study and future directions will also be discussed. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T25.00007: Acoustic and flow measurements of porous plate designs for aerodynamic noise mitigation John R Kershner, Thomas F Geyer, Justin W Jaworski The acoustic and flow effects of flat plates with chordwise perforations are experimentally investigated. A dimensionless parameter known to control the scaling of noise generation in a quiescent fluid is applied to the analysis of sound generated by a turbulent boundary layer over the flat plates. Multiple perforation designs are tested and compared to a nonporous reference plate in an open jet aeroacoustic wind tunnel. DAMAS acoustic beamforming is performed in the trailing-edge region and other sectors of the plate, and the flow field of the plates is investigated using hot-wire anemometry measurements in the near-wake and boundary layer. An increase in the porosity parameter leads to an decrease in noise generation at low frequencies and an increase at high frequencies for the porosity designs considered. In particular, sound pressure levels of the trailing edge region are reduced by up to 20 dB at low frequencies and are increased by up to 18 dB at high frequencies. The presence of porosity increases the turbulence intensity near the plate surface, which may be responsible for the observed high-frequency excess noise created by the pores themselves. Nevertheless, trailing-edge porosity is shown to reduce the overall sound pressure level by up to 4 dB. |
Monday, November 25, 2024 6:16PM - 6:29PM |
T25.00008: Comparison of Turbulent Jet Noise and Fluctuating Flow Field REAL J KC, Brian R Elbing, Douglas Fox Tornadoes emit sound at frequencies below human hearing and there is evidence that it carries information about the tornado including its formation. A current theory for the fluid mechanism responsible for the production of this sound relies on latent heat causing an amplification of turbulent sounds within the tornado. The current project aims to provide experimental evidence for this amplification by examining the impact of latent heat within a small turbulent jet. This presentation will present preliminary work measuring the fluid flow within a dry turbulent jet using particle image velocity (PIV) and hotwire anemometry. The turbulent fluctuations will be compared with the local acoustic production using a 40-microphone acoustic camera that using beamforming can isolate specific sources of noise production. This work will then extend to do comparative analysis with and without the latent heat effect. |
Monday, November 25, 2024 6:29PM - 6:42PM |
T25.00009: Acoustically enhanced porous media enables dramatic improvements in filtration performance Andres Barrio Zhang, Sudharshan Anandan, Akshay Deolia, Ryan B Wagner, David M Warsinger, Arezoo M Ardekani Acoustics have previously been leveraged to improve air purification with fiber filters, but little is known about how the arrangement of the fibers influences the acoustic effects, particularly for non-agglomerative purification performance relevant to fine and ultrafine pollutants. Here, we explore performance enhancements to fiber filters by applying external standing acoustic waves. We investigate the effects of the porous media arrangement in ordered (aligned and staggered) and disordered fiber media by building a multiphysics model, incorporating thermos-viscous acoustics, laminar flow, and particle tracing. Particles are modeled as point forces to isolate acoustic radiation forces and streaming. Attractive acoustic radiation forces dominate in the porous domain, leading to increased particle/boundary interactions. We find that the average acoustic radiation forces scale linearly with the average scattered acoustic pressure by the fiber medium. The scattered pressure varies depending on the fiber arrangement, indicating that there is an optimal design to increase the performance of acoustic-induced effects. We show a dramatic increase in performance efficiency, up to two orders of magnitude (123 times) for a staggered domain. This work has important applications to further advance acoustically enhanced filtration as a compelling solution for micro/nanoparticle separation processes. |
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