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 ZC26: Geophysical Fluid Dynamics: Atmospheric III |
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Chair: Eric Pardyjak, University of Utah Room: 251 D |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC26.00001: Atmospheric Sensing and Observations During The 2024 Total Solar Eclipse Kate B Spillman, Emalee Hough, Zach Yap, Brian R Elbing, Jamey D Jacob Oklahoma State University was one of 52 teams that studied the 2024 total solar eclipse as part of the NASA Nationwide Eclipse Ballooning Project (NEBP). Balloons were launched from Broken Bow, OK, which was within the path of totality. This included the launch of two heliotropes, each carrying different payloads. Heliotropes are a type of solar balloon that is designed to float within the lower stratosphere (~20 km) during typical daytime conditions. The first payload included three cameras and sensors for measuring temperature, pressure, humidity, and solar radiation. The primary objective of this payload was to quantify the balloon performance due to the rapid change in solar radiation during the eclipse. The second payload carried two infrasound sensors with different inlet configurations. Infrasound is sound pressure waves at frequencies below the threshold of human hearing (<20 Hz). In the past, ground-based infrasound sensors have detected the surface pressure fluctuations induced by gravity waves produced from the eclipse-induced cooling. Consequently, for the current study, a three-sensor infrasound array was also deployed on the ground within the path of totality. This presentation will discuss the instrumental payloads, launch day operations, and data analysis. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC26.00002: UAS-Based Observations of Eclipse Impact on the Atmospheric Surface Layer Sean C.C. Bailey, Suzanne W Smith, Tracy Knowles A solar eclipse provides a unique opportunity to observe the response of atmospheric turbulence to an approximate step change in solar radiation. To assess the unsteady changes in the atmospheric surface layer introduced by a solar eclipse, a measurement campaign was conducted in Bloomington, Indiana, on April 8, 2024. The weather at this location resulted in a high temperature of 24°C and fair conditions prior to the eclipse, resulting in a measurable impact of the eclipse. Several measurement systems were deployed, including a fixed-wing uncrewed aerial vehicle (UAV), a quadrotor UAV, radiosondes, and ground-based sensors. |
Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC26.00003: Role of Diurnal Atmospheric Stratification in Plume Development Ritambhara Raj Dubey, Neda Yaghoobian Buoyant plumes, propelled by concentrated heat and mass sources, are prevalent in nature. Originating from phenomena such as fires, volcanic eruptions, chimney smokestacks, and sea ice melting, they represent a crucial class of problems in atmospheric and ocean dynamics. The behavior of turbulent buoyant plumes is influenced by the characteristics of the plume source, topography, and background flow conditions. The atmospheric boundary layer, which varies diurnally from a few hundred to several thousand meters in height, significantly impacts the background flow conditions and consequently the plume dynamics. This numerical study aims to investigate the effect of diurnally varying atmospheric stratification on the dynamics of buoyant scalar plumes using large-eddy simulations. By understanding the mechanisms governing the initiation, development, and behavior of plume trajectories, this study aims to improve the understanding of plume dynamics and contribute to better planning, management, and mitigation of their adverse effects. |
Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC26.00004: Examination of Physical Coupling Processes in Wildfires Through High-fidelity Ensemble Simulations Matthias Ihme, Qing Wang, Cenk Gazen, Karl Toepperwien, Yi-Fan Chen, John Anderson Wildfires pose serious threats to society, environment, and ecosystems as they can disrupt, damage, and destroy infrastructure, services, and properties. To examine the complex interaction of wildfires, arising from coupling processes between combustion, atmospheric flow, heat-transfer, topography, and fuel properties, we present a simulation framework that integrates a high-fidelity ML-enabled simulations framework for wildfire predictions with a sampling technique to perform high-resolution ensemble simulations of large-scale wildfire scenarios. The simulation results are compared to existing experimental data for fire acceleration, mean rate of spread, and fireline intensity. Strong coupling between key compounding parameters (wind speed and slope) are observed for fire spread and intermittency. Scaling relations are derived and presented to delineate regimes associated with plume-driven and convection-driven fire spread. |
Tuesday, November 26, 2024 1:42PM - 1:55PM |
ZC26.00005: Investigating extreme fire behavior in complex terrain using high-resolution large-eddy simulations on ML-enabled compute infrastructure Karl Toepperwien, Qing Wang, Yi-Fan Chen, Cenk Gazen, John Anderson, Matthias Ihme Wildland fires in regions of complex terrain are often associated with extreme fire behavior. Understanding the interaction between complex terrain and atmospheric flows that results in these extreme conditions is thus an important endeavor. In particular, sloped terrain can lead to highly dynamic wind patterns, thereby enhancing turbulence which in turn directly affect all modes of heat transfer, resulting in more severe fire behavior. |
Tuesday, November 26, 2024 1:55PM - 2:08PM |
ZC26.00006: Application of an Immersed Boundary Method to generate boundary layer turbulence and unsteady wind fields Jianyu Wang, Catherine Gorle Large-eddy simulations of wind engineering problems frequently rely on a combination of artificial turbulence generation and a rough wall function on the ground surface to generate a neutral surface layer flow. This approach may fall short when the aim is to capture non-standard wind conditions. Examples range from modeling the roughness sublayer for simulations of low-rise buildings to modeling profiles that deviate from the typical log-law shape or modeling unsteady events such as tornados. To address these challenges, this study explores the use of an Immersed Boundary Method (IBM) to simulate the interaction between the wind flow and a combination of roughness elements, spires, or louvers positioned in the flow development section of the computational domain. The implementation is tested on two set-ups: one with roughness elements that will generate a roughness sublayer for low rise building applications, and one with louvres that generate an unsteady velocity profile. In the first case, we quantitatively established the relationship between the velocity profile of the complete ABL inner layer and the distribution characteristics of roughness elements. At the same time, we achieved the simplification of the set-up of numerical analysis of a wide range of wind engineering flows without compromising on computational efficiency. In the second case, we compared with the results of wind tunnel experiments, demonstrating the feasibility and convenience of applying IBM in non-steady flow simulations. |
Tuesday, November 26, 2024 2:08PM - 2:21PM |
ZC26.00007: Investigating the Impact of Coastal Topography on Marine Fog Dynamics Using Large-Eddy Simulations Shubham Mittal, Anup Barve, Lian Shen This study aims to investigate the effect of coastal land on the behavior of marine fog, using Sable Island in the Atlantic Ocean as an example. Marine fog is an important meteorological phenomenon with significant implications for coastal regions, impacting visibility, transportation, and ecological processes. Employing wall-modeled large-eddy simulations, we delve into the dynamics of marine fog over Sable Island to improve our understanding of the influence of coastal topography on the behavior of fog. |
Tuesday, November 26, 2024 2:21PM - 2:34PM |
ZC26.00008: Mean and Turbulence Dynamics in Hurricane Boundary Layers Mostafa Momen While hurricanes have been the most expensive natural disaster in US history, our understanding of the turbulence dynamics of these geophysical flows is limited due to the lack of sufficient measurements and high-resolution simulations. To bridge this knowledge gap, we will employ high-resolution large-eddy simulations (LESs) to characterize the impacts of the radius, gradient wind, and surface roughness and waves on hurricane's mean and turbulence dynamics. Our results show that increasing the Rossby number (rotation) increases the hurricane's maximum jet velocity, decreases the boundary layer height, and reduces the size of coherent turbulent structures at the same elevation. It was also found that as the Rossby number increases, the shear production of turbulence is enhanced near the wall and decreased away from the wall, indicating turbulence suppression by rotation. Moreover, the implications of such changes on real hurricane forecasts of weather models will be briefly shown by adjusting the diffusion magnitude in the atmospheric boundary layer. Using these insights, we were able to significantly improve the intensity forecasts of real major hurricanes by an average of ~30% in five considered cases. The findings of this research provide new insights into the turbulence dynamics of hurricanes, and can guide the development of more accurate forecasting models for hurricane flows. |
Tuesday, November 26, 2024 2:34PM - 2:47PM |
ZC26.00009: Abstract Withdrawn
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Tuesday, November 26, 2024 2:47PM - 3:00PM |
ZC26.00010: Coherent organization of a passive scalar from a point-source in a turbulent boundary layer Isaiah Wall, Gokul Pathikonda The spatial organization of a passive scalar plume originating from a point source in a boundary layer is studied to understand its meandering characteristics. We focus shortly downstream of the isokinetic injection (1.5 ≤ x/δ ≤ 3, δ being boundary layer thickness) where the scalar concentration is highly intermittent, the plume rapidly meanders, and breaks-up into concentrated scalar pockets due to the action of turbulent structures. Two injection locations were considered: the center of logarithmic-region and the wake-region of the boundary layer. Simultaneous quantitative planar laser-induced fluorescence (PLIF) and particle-image velocimetry (PIV) were performed in a wind-tunnel, using acetone vapors to measure scalar mixture fraction and velocity fields. Single- and multi-point statistics were compared to established works to validate the diagnostic novelties. Additionally, the spatial characteristics of the plume intermittency were quantified using `blob' size, shape, orientation and mean concentration. It was observed that straining and break up were the primary plume-evolution modes in this region, with little small-scale homogenization. Further, the dominant role of coherent vortex motions in meandering and break-up of the plume was evident. Their action is found to be the primary mechanism by which the scalar injected within the log-region is transported away from the wall (`large meander events'). Strong spatial correlation was observed in both instantaneous and conditional fields between the high scalar concentration regions and the individual vortex heads. This coherent transport was weaker for wake-injection case, where the plume only interacts with outer vortex motions. A coherent-structure based mechanism is suggested to explain these transport mechanisms. |
Tuesday, November 26, 2024 3:00PM - 3:13PM |
ZC26.00011: Revealing the drivers of turbulence anisotropy over complex terrain with interpretable machine learning. Samuele Mosso, Karl Lapo, Ivana Stiperski Turbulence anisotropy has gained attention in recent years for its role in surface layer atmospheric turbulence. The degree of anisotropy yB, retrieved from anisotropy invariant analysis, has been introduced as an additional non-dimensional parameter into the flux-variance, flux-gradient and spectral surface scaling relations of Monin-Obukhov Similarity Theory (MOST). This new approach allowed to explain the observed scatter in the scaling relations both over flat and highly complex terrain, thus extending MOST outside of its original range of validity. However, how to predict yB in a range of realistic terrain and stability conditions, remains an open question. |
Tuesday, November 26, 2024 3:13PM - 3:26PM |
ZC26.00012: The effect of artificially induced Crow instability on contrail radiative forcing Tania Ferreira, Denis-Gabriel Caprace, Karim Shariff, Roberto Paoli Aircraft contrails are believed to have a net warming effect on the earth that is greater than that due to aviation CO2, albeit with a large uncertainty. This is because on average they absorb more upward longwave radiation from the earth's surface than they reflect downward shortwave solar radiation back to space. We perform time-developing simulations in a stratified atmosphere to assess whether artificially inducing the Crow instability of trailing vortices via out-of-phase deflection of two ailerons on each wing (so as to maintain a constant lift) can reduce contrail radiative forcing. The initial condition consists of (a) a vortex sheet with an axially varying strength to mimic the effect of aileron deflection; (b) hot vapor laden jets that are initially perturbed; and (c) Lagrangian particles in the jets that subsequently grow due to ice deposition. Separate simulations are performed with the compressible CharLES code and the incompressible Vortex Particle-Mesh (VPM) code. Radiative forcing is assessed using a parameterization in terms of optical depth. We find that for a range of surface albedos and zenith angles of the sun, particle redistribution by the Crow instability in the forced case, leads to increased radiative forcing. This is due to an increased spanwise extent of the contrail where vortex reconnection occurs. |
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