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 ZC23: Experimental Techniques: General |
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Chair: Xiaowei He, University of Utah Room: 251 A |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC23.00001: Uncrewed Aerial Vehicle (UAV) measurements of atmospheric boundary layer turbulence. Nikolay Gustenyov, Sean C.C. Bailey A semi-autonomous Uncrewed Aerial Vehicle (UAV) was used to measure atmospheric boundary layer turbulence under variable stability conditions. Measurements were taken both with a five-hole probe capable of resolving all three wind components at a frequency of 50Hz and single-sensor hot-wire probe sampled at 20kHz. The UAV was tasked with flying a "racetrack" trajectory with respect to the ground, with the major axis consisting of straight-line flight over the ground encompassing a distance of 800m. The aircraft positions (pitch, roll and yaw) and their rates were constantly monitored and recorded which, when combined with the five-hole probe data, allowed extracting three wind components. The data from this probe was also used to calibrate the hot-wire probe in-situ, which allowed extension of the frequency content from the five-hole-probe system to higher frequencies. The collected data provides turbulence statistics at high Reynolds number with an advantage of scanning an atmospheric flow by moving through an air mass at velocities higher than the wind. While this method has a great potential, there are no widely-accepted procedures to analyze spatio-temporal measurements of this nature, including application of Taylor's frozen flow hypothesis, and extracting longitudinal and transverse wind components. One challenge is to compensate for a reduced hot-wire sensitivity at variable angles with respect to an air flow. The goal of the current work is to develop and propose a reliable procedure in preprocessing such data and then use it to investigate the structure functions scaling for high Reynolds number atmospheric flows. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC23.00002: Autonomous Drone Swarming for 3D Mapping of Atmospheric Particle Transport from Micrometer to Kilometer Scale Jiarong Hong, Srijan Pal, Shashank Sharma, Nikil Krishnakumar, Sujeendra Ramesh, Rammesh A Saravanan, Lalitaditya Divakarla Understanding particle dispersion from wildfires is essential for modeling its impact on regional air quality and global climate. However, field characterization of the complete spectrum of particle behaviors—from individual particles at the microscale to kilometer-spanning plumes—presents significant technical challenges. Here, we introduce an autonomous drone swarm system to address this challenge. The system features a manager drone that coordinates multiple worker drones, each equipped with computer vision cameras for navigation and plume imaging, and holographic microscopy sensors for detailed analysis of particle properties such as concentration, morphology, and types. Specifically, the manager drone analyzes particle plume structure in real-time and uses flow-intelligent AI to guide the worker drones, optimizing their formation and navigation paths to reconstruct 3D smoke plume geometry and particle distribution. This system, developed using a simulated environment incorporating fluid dynamics and drone operation, was successfully deployed during the Cedar Creek prescribed burn experiments, demonstrating its efficacy in real-world applications. Our work provides a versatile tool not only for the fundamental study of atmospheric particle transport phenomena, such as dust, volcanic ash, and pollen dispersion, but also for practical applications such as forest fire response and other environmental monitoring tasks. |
Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC23.00003: ABSTRACT WITHDRAWN
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Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC23.00004: Go with the Flow II: Micro Aerial Vehicles as Active Particles in the Atmospheric Boundary Layer Nathaniel Simon, Skywalker Li, Nick Conlin, Nathaniel J Wei, Anirudha Majumdar, Marcus Hultmark Micro aerial vehicles have transformative potential in applications ranging from package delivery and infrastructure inspection to large-scale field measurement campaigns. Operating in the atmospheric boundary layer, these vehicles must be able to react to and navigate in constantly changing conditions. The prevailing approach is to sense and reject all disturbances from the desired condition. In this talk, we examine whether selective amplification of favorable disturbances can actually improve vehicle performance. Such improvements could mean improved vehicle range and endurance, or more efficient coverage of a desired measurement volume. This study is enabled by a suite of hardware and controller improvements to our LaDrone platform, including brushless motors, a disturbance-accepting controller, and an integrated antenna design. |
Tuesday, November 26, 2024 1:42PM - 1:55PM |
ZC23.00005: A Probabilistic Approach for Correction of Multi-Hole Directional Probes for Varying Flow Fields. Lakshya Bhatnagar, Guillermo Paniagua, Kush Sreen, Andrea Ruan Multi-hole directional probes are commonly used in experimental fluid mechanics to assess flow angles, total and static pressure. They need to undergo calibration to relate these quantities to the pressure readings in the measurement holes. This relationship is however dependent on the flow Mach and Reynold's number. It is also influenced due to flow distortion induced by the probe or interaction between probe and test article, especially in confined flows. Since it is not always feasible to calibrate in a similar flow field as the test, a correction methodology is developed that combines flow features and trends obtained numerically with experimental calibration. RANS simulations are run for an ideal probe for the actual test condition and results are used to train a Bayesian model to reduce the number of CFD simulations required for the range of the calibrated angle. This is used to provide enough data to generate a correction model. The correction model is then mapped to an experimental calibration, done at another Mach and Reynolds number, and is used to predict the true probe calibration at the required flow conditions. This methodology is compared against experimental calibration done at different flow conditions. |
Tuesday, November 26, 2024 1:55PM - 2:08PM |
ZC23.00006: Sensitivity limits of background oriented schlieren (BOS) with a projected background Maria Nicola D'Orazio, Michael J Hargather, Philip Boudreaux Background-oriented schlieren (BOS) requires a background pattern against which a schlieren object is imaged. Generally these patterns are painted, printed, or projected behind the schlieren object. Here a projected dot pattern, which is projected through the schlieren object, was explored. This arrangement results in double refraction of the pattern, both on the initial projection and on the return light to the camera, similar to a single mirror schlieren system. The goal of the present work is to quantify the sensitivity of the system. A high resolution camera was used to image helium jets in air against both projected and traditional BOS backgrounds. Distances between the helium plume and and both background types were varied to determine the range at which sensitivity was lost in each arrangement. The resultant pixel shifts caused in the BOS backgrounds were calculated using optical flow methods, and the results were compared against each other. While traditional BOS backgrounds were found to have a higher sensitivity, the projected BOS backgrounds have the potential to be applied in a wider range of experimental setups. |
Tuesday, November 26, 2024 2:08PM - 2:21PM |
ZC23.00007: Space- and time-resolved dissipation measurement in wall-bounded turbulence Sébastien Aumaitre, Enzo Francisco Dissipation is a key quantity of turbulent flow since, for instance, it sets the energy consumption of vehicles and pressure losses in pipes. At geophysical scale, it plays a role in energy balance and transport efficiency in climate models. At a fundamental level, the dissipative structures might drive the intermittency. Nevertheless, it is very difficult to measure it experimentally. Indeed, it necessitates the full spatial derivative of the entire velocity components. This requires a resolution beyond the reach of current velocimetry techniques. Direct Numerical Simulations fail also to estimate such quantity over long time at large Reynolds number because of numerical cost, and thus may underestimate rare events. Here we present an experimental technics allowing us to measure directly the norm of the strain-rate tensor, i.e the root mean square of the dissipation. The method is based on the diffusing wave spectroscopy (DWS) applied on a turbid fluid. With the use of a fast camera focused on the fluid interface, we are able to get a spatio-temporal map of the dissipation. |
Tuesday, November 26, 2024 2:21PM - 2:34PM |
ZC23.00008: Color filtered schlieren for concentration and density measurements of a helium-iodine plume Maria J Ortiz, Michael J Hargather Schlieren imaging is used to image refractive disturbances within a flow field, but it does not provide details about the chemical composition of the flow. Simultaneous use of schlieren and imaging spectroscopy was developed and shown to provide insights into the complex chemical environment of gas flows using absorption spectroscopy. Continuing this work, the use of two simultaneous schlieren views of the test field were used to determine chemical composition without the use of a spectrometer. Tests were conducted using laminar helium gas plumes infused with iodine gas. The light exiting the schlieren system was split between two cameras. A unique bandpass filter was placed in front of each camera to limit the wavelengths of light reaching the camera, thus creating a two-wavelength spectral map of the flow. Comparing the light intensity changes and absorption between these two wavelengths allowed calculation of iodine concentration throughout the plume images. This implementation in combination with quantitative schlieren imaging allowed for measurement of the local refractive field and ultimately density. |
Tuesday, November 26, 2024 2:34PM - 2:47PM |
ZC23.00009: An Advanced Aircraft Deicing Analysis: Supercooled Liquid Dynamics under Ultrasonic Frequency and Surface Roughness Effects Kevin Thomas Fernandez, Olivier COUTIER-DELGOSHA, Joe El Ghossein Structural icing presents a significant engineering challenge, prompting extensive research into preventive measures. Traditional solutions, such as high-power systems and anti-icing chemicals, face complexities due to supercooled water droplets freezing, increasing weight, drag, and de-icing power requirements. This study introduces a novel approach combining ultrasonic frequency vibrations (UV) with piezoelectric (PZT) actuators and explores surface roughness variations on a superhydrophobic surface. Conducted in a controlled chemistry lab environment, surface roughness was determined through optical imaging, and static and dynamic drop tests for a 2mm droplet were recorded using a Photron FASTCAM SA.1 at ambient and supercooled temperatures. A cryogenic setup with precise temperature control was developed, examining heights up to 61 cm and frequencies up to 51 kHz to determine optimal parameters. Insights from experiments at Argonne National Laboratory and previous project work informed the study, emphasizing ultrasonic/high-frequency actuation for atomization and droplet dynamics at temperatures below -10°C. The study also utilized Abaqus FEA to validate the frequency response function (FRF) of the PZT attached to a plate. The methodology involved adjusting frequency (as single, sweep and arbitrary waves), amplitude, and velocity parameters, with aluminum as the substrate for accuracy and reliability. This research aims to tackle structural icing through the innovative combination of ultrasonic and PZT actuators, exploring the impact of surface roughness and droplet dynamics during the water-to-ice transition. The custom-built cryogenic environment with ultrasonic wave actuation using disk actuators offers promising solutions for more efficient and cost-effective de-icing methods. |
Tuesday, November 26, 2024 2:47PM - 3:00PM |
ZC23.00010: FIEVel: a Fast InExpensive Velocimeter based on an optical mouse sensor Eli Silver, Robert Hunt, Daniel M Harris Velocity measurement in fluids is essential for many applications spanning research, education, and industry. This presentation will discuss the development and application of FIEVel, a low cost, high sample rate, optical fluid velocimeter. State-of-the-art methods such as hot-wire anemometry, laser doppler velocimetry, acoustic doppler velocimetry, and particle image velocimetry (PIV) are typically intrusive, offer a low sample rate, or have a high cost. Using an optical sensor developed for commercially available computer mice, we demonstrate nonintrusive, time-resolved, 2-component, pointwise velocity measurements in the bulk of a flowing fluid at sample rates over 6 kHz, validated by direct comparison with high frame rate PIV. Our device uses inexpensive and interchangeable lenses intended for webcams and a custom 3D-printed housing with integrated focus adjustment. The device design, build documentation, supporting software, and operating guidelines are being released as an open-science hardware project and can be reproduced for less than $100 in materials. As an application example, we showcase the sensor's ability to resolve temporal spectra in grid generated turbulence. |
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