Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session P30: Geophysical Fluid Dynamics: Atmospheric |
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Chair: Alexis Kaminski, UC Berkeley Room: North 229 B |
Monday, November 22, 2021 4:05PM - 4:18PM |
P30.00001: SST k-omega Simulations of the Atmospheric Boundary Layer Including the Coriolis Effect Christiane Adcock, Marc T Henry de Frahan, Jeremy Melvin, Ganesh Vijayakumar, Gianluca Iaccarino, Robert Moser, Michael A Sprague For large-scale structures in the atmospheric boundary layer (ABL), the Coriolis effect and near-wall turbulence can meaningfully impact aerodynamic performance. For example, the Coriolis effect and blade boundary layers affect wind farm power production. RANS simulations of the ABL typically use the k-epsilon turbulence model, which has been modified to accurately capture the Coriolis effect but does not perform well near walls. The SST k-omega turbulence model accurately predicts near wall turbulence but not the Coriolis effect. We propose a modification to SST k-omega to better represent the Coriolis effect. We contrast how to modify k-epsilon and SST k-omega for the Coriolis effect. Finally, we compare k-epsilon and SST k-omega simulations of the ABL, including the Coriolis effect, with large eddy simulations and measurements. |
Monday, November 22, 2021 4:18PM - 4:31PM |
P30.00002: Understanding Low Level Jets in the US Atlantic Offshore Emily K de Jong, Eliot Quon, Shashank Yellapantula Low level jets (LLJs) in the atmosphere exhibit a local windspeed maximum in the boundary layer, with positive shear beneath the jet and negative shear above the jet. Wind turbines tend to experience increased loads with varying wake recovery characteristics in the presence of an LLJ, therefore understanding the mechanism and impact of LLJs is crucial to wind energy development. The US Mid-Atlantic offshore region is a huge potential wind energy resource, yet LLJs in this area are poorly understood. In this study, we use the Weather Research and Forecasting model (WRF) plus lidar buoy data to identify case studies for LLJ events in 2020 in the New York Bight. A reduced order model is presented to explain the onset of these events based on the competing effects of baroclinicity and eddy diffusivity. Finally, using the macro-scale WRF, we drive a micro-scale large eddy simulation (LES) to generate a more detailed characterization of the Marine Boundary Layer during an LLJ. Gaining a better understanding of LLJs and their impacts on offshore wind in the mid-Atlantic is crucial for a transition toward renewable energy. |
Monday, November 22, 2021 4:31PM - 4:44PM |
P30.00003: Wind and Gust Sensing Requirements for Advanced Aerial Mobility Applications Jamey D Jacob, Suzanne Smith The use of small unmanned aircraft systems (sUAS) as a tool for use in atmospheric observations for integration of urban air mobility (UAM) solutions as well as unmanned traffic management (UTM) system development and implementation. However, the challenges of urban wind field sensing include high spatial turbulence gradients, high turbulence magnitudes, and degraded position references, all of which complicate the traditional approach. Swarming and mesh network topologies are attractive for integrating additional sensing platforms into this measurement challenge. Since understanding these wind fields is still a topic of research, and this turbulence is a large component of the wind field being sensed, a detailed understanding of gust responses is necessary to provide accurate control. Inertial estimation approaches that incorporate observational measurements and errors to provide measurement of the local wind field will improve their estimation accuracy by incorporating mechanisms to modulate the sensitivity based on local wind magnitudes. This presentation discusses integration approaches and field tests for utilizing UAS to provide real-time data to enable UAM and UTM operations; improving the resolution and accuracy of comprehensive wind field estimation is critical to improve safety and operational efficiency. |
Monday, November 22, 2021 4:44PM - 4:57PM |
P30.00004: Data Collection from Zero pressure solar balloons for Gravity Wave Detection Zach Yap, Emalee Hough, Jamey D Jacob, Brian R Elbing, Léo Martire, Siddharth Krishnamoorthy, Daniel Bowman The discovery of atmospheric gravity waves and their capability to transfer energy through the atmosphere has accelerated the interest in weather balloon soundings and data collections to locate and characterize the generation of gravity waves. By looking into the formation of the gravity waves, caused by wind shear, convection, or topography, one is able to get a better idea of how they impact atmospheric conditions, with the intent of using the information to improve weather predictions. Previous research has been focused on using weather balloons and radiosondes to identify gravity waves; the drawback of this method is that it only takes a thin slice of the atmosphere (~1.5-hour flights). Presently, we are using zero pressure solar balloons with high accuracy GPS IMUs and radiosondes to take atmospheric readings while in flight giving a longer window (~8-hour flights) to collect data and detect gravity waves. Currently, the wind data is studied using a combination of the Morlet wavelet transform and the hodograph methods to identify gravity waves in the data. The data is then run through an analysis that detects the location, frequency, propagation direction, and amplitude which can be used to distinguish the cause. This research accomplishes this by comparing examples from atmospheric background readings to assist in identifying the source of the gravity waves. |
Monday, November 22, 2021 4:57PM - 5:10PM |
P30.00005: Infrasound Detection from Zero Pressure Solar Balloons Emalee Hough, Zach Yap, Jamey D Jacob, Brian R Elbing, Léo Martire, Siddharth Krishnamoorthy, Daniel Bowman Infrasound is generated from a multitude of sources ranging from earthquakes and volcanoes to thunderstorms and waves on the ocean. Due to these phenomena, the range for sources in infrasound can be a useful tool for identifying and characterizing a planet's interior structure and atmospheric behavior. The vertical ground motion of seismic waves launches infrasonic acoustic waves into the atmosphere and the resulting excited waves propagate upward. The amplitude of waves increases with height owing to conservation of momentum, because the atmosphere is rarefied exponentially with height. Multiple detectors allow cross correlation to triangulate location of the source. Infrasound travels long distances in the atmosphere and can be used on a solar balloon for remote sensing on alien planets like Venus. Venus is chosen as an ideal planet for this type of testing because the surface of Venus is so inhospitable to landers (surface temp > 460°C). Whereas the middle atmosphere of Venus is much more hospitable (0-100°C) making remote sensing with balloons an easier challenge than a lander. The downside to the wide range of these sources is that it requires a large data set to help characterize which infrasound source we are receiving. To be able to demonstrate suitability for the aerial seismology ideal, additional data sets are needed. This is done by a continuous balloon campaign that is taking place from June to the end of September 2021 over the seismogenic zone in Oklahoma, where multiple balloon launces a week will take place. We will discuss the flight system, instrumentation, and details of the campaign design. |
Monday, November 22, 2021 5:10PM - 5:23PM |
P30.00006: Atmospheric Boundary Layer Characterization via UAS Wind Speed Measurements Zachary D Morrison, Trevor C Wilson, Brian R Elbing Unmanned Aerial Systems (UAS) have become increasingly involved in weather monitoring and prediction. UAS can be outfitted with sensors to measure various atmospheric properties such as temperature, velocity, and humidity. Interference between the UAS propulsion systems and these sensors can contaminate data sets. To mitigate this issue, the sensor must be placed in a position where contamination is minimal. Previous work (Brenner, 2021) delineated methodology to determine the optimal placement for a wind velocity sensor. The current work aims to utilize this optimal sensor placement to obtain trusted velocity measurements from a UAS. These measurements, along with stationary tower velocity measurements, will be used to characterize the local atmospheric boundary layer. The characterization is done by analyzing wind velocity signals from both the tower and the UAS. Results shown will be a statistical analysis between both the stationary tower and UAS. Specifically looking at length and time scales of the atmospheric boundary layer. |
Monday, November 22, 2021 5:23PM - 5:36PM |
P30.00007: Universal Return to Isotropy of Inhomogeneous Atmospheric Boundary Layer Turbulence Ivana Stiperski, Gabriel G Katul, Marc Calaf A recalcitrant problem in the physics of turbulence is the representation of the tendency of large-scale anisotropic eddies to redistribute their energy content with decreasing scales, a phenomenon referred to as return to isotropy. An unprecedented dataset of atmospheric turbulence measurements covering flat to mountainous terrain, stratification spanning convective to very stable conditions, surface roughness ranging over several orders of magnitude, and Reynolds numbers that far exceed the limits of direct numerical simulations and laboratory experiments was assembled for the first time and used to explore the scalewise return to isotropy. The multiple routes to energy equipartitioning among velocity components are shown to be universal once the initial anisotropy at large scales, linked to turbulence generation, is accounted for. |
Monday, November 22, 2021 5:36PM - 5:49PM |
P30.00008: A model for large-scale deployments of CO2 Direct Air Capture systems Paolo Luzzatto Fegiz, Samaneh Sadri Direct Air Capture (DAC) is an emerging technology for removing carbon dioxide from the atmosphere, by deploying “absorbers” that implement a chemical reaction with ambient air. Recent DAC research has focused primarily on chemistry and heat transfer processes, in order to optimize the performance of individual CO2 absorbers. However, large DAC arrays will introduce an additional issue: behind the first absorber, subsequent ones must operate with inlet air that has progressively lower CO2 concentration, thereby increasing their energy requirement for capture and separation. Minimizing this adverse effect requires increasing the spacing between absorbers, leading to increased land requirements and deployment costs. Furthermore, there appear to be no published models for predicting the performance of such large DAC arrays. To address this issue, we introduce a multi-scale model for the aerodynamics of large-scale DAC systems. We obtain an explicit expression for CO2 capture by a large array, which combines single-absorber design and capture processes with effects of wind speed, atmospheric turbulence, and layout geometry. Our findings provide a quantitative link between atmospheric dynamics and the performance of large-scale DAC deployments. |
Monday, November 22, 2021 5:49PM - 6:02PM |
P30.00009: Contaminant Dispersion in Oklahoma City - High Fidelity Simulations and Comparison with Magnetic Resonance Measurements Mark F Owkes, Ty Homan, Michael J Benson, Christopher Elkins, Andrew J Banko The intentional or accidental release of a contaminant in an urban environment has the potential to be harmful for a large population. However, predicting the dynamics of the contaminant plume is complicated due to the complex geometry of the urban buildings. Many studies have been performed that provide velocity and concentration data at a few discrete points within the complex flow. This work leverages a rich four-dimensional (three-spatial and one-temporal) measurement taken with magnetic resonance imaging (MRI). The experiment was conducted on a 1:2206 scaled model of downtown Oklahoma City within a water tunnel and provides contaminant concentration and three components of velocity at 1.6 million locations and 12 times. This dataset is compared against LES simulations performed with the same geometry and boundary conditions. The one-to-one comparison between experimental measurements and simulations allows us to 1) explore the physics of the dispersion in the urban environment and 2) assess the LES model's predictive capabilities. In particular, velocity statistics, contaminant isosurfaces, and flow intricacies near the buildings are investigated. |
Monday, November 22, 2021 6:02PM - 6:15PM |
P30.00010: Time-resolved Three-dimensional Measurements of Scalar Dispersion from Two Transient Sources in a Mock Urban Geometry Ty Homan, Michael J Benson, Christopher Elkins, Andrew Banko The study of atmospheric dispersion in the urban environment is complicated by building geometries, changing conditions, street canyons, and a variety of other factors. Further complexity is introduced by contaminant releases involving multiple close sources. Magnetic Resonance Imaging (MRI) techniques were applied to a mock urban geometry with two simultaneous transient contaminant releases as a means to provide experimental results with well qualified boundary conditions that can be leveraged to improve simulations of similar flows. The MRI techniques produced three-component velocity and concentration measurements, arranged in a three-dimensional array comprised of over 2.5 million measurement locations for each of 14 successive time intervals within the periodic transient release cycle. The spatial resolution of the measurements provides insight into complex flow and dispersion mechanisms, while the time-resolved nature of the measurements enables analysis of fundamental transport mechanisms. The data sets are expected to be of particular utility for computational fluid dynamics (CFD) model evaluation and validation, as well as for the testing of source term estimation methods. An investigation of the detailed experimental results is presented, demonstrating particular advantages of the dataset towards model comparison efforts. |
Monday, November 22, 2021 6:15PM - 6:28PM |
P30.00011: Shear-stress and temperature-flux cospectra in the convective atmospheric surface layer using matched asymptotic expansions Chenning Tong In our recent work we predicted the shear-stress and temperature-flux cospectra in the surface layer using the multi-point Monin-Obukhov similarity and dimensional analysis. In this work we predict these cospectra using matched asymptotic expansions employing their transport equations. The outer (large) scales are shown to have the mixed-layer scaling. As the wavenumber increases the scaling of the dominant terms in the cospectral equations change, resulting in a singular perturbation problem with two inner scales. Matched asymptotic expansions up to the second order are obtained as a solution, which gives the lead-order scaling of the cospectra in two scaling ranges and the corrections due to finite values of the scale separations. |
Monday, November 22, 2021 6:28PM - 6:41PM |
P30.00012: Collisions of micron-sized, charged water droplets in still air Gustav Magnusson, Anshuman Dubey, Reece Kearney, Gregory P Bewley, Bernhard Mehlig We investigate the effect of electrical charge on collisions of hydrodynamically interacting, micron-sized water droplets settling through quiescent air. The relative dynamics of charged droplets is determined by hydrodynamic interactions, particle and fluid inertia, and electrostatic forces. We analyse the resulting relative dynamics of oppositely charged droplets by determining its fixed points and their stable and unstable manifolds. The stable manifold of a saddle point forms a separatrix that separates colliding trajectories from those that do not collide. The qualitative conclusions from this theory are in excellent agreement with experiments. This talk is based on the preprint "Collisions of micron-sized, charged water droplets in still air" by G. Magnusson, A. Dubey, R. Kearney, G. P. Bewley, and B. Mehlig (arxiv:2106.11543). |
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