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 R32: Convection and Buoyancy-Driven Flows: General |
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Chair: Oleg Schilling, Lawrence Livermore National Laboratory Room: 255 D |
Monday, November 25, 2024 1:50PM - 2:03PM |
R32.00001: Convection driven by a nonuniform radiative internal heat source in a cavity Mona Rahmani, D. Mark Martinez While most studies of convection driven by an internal heat source in a fluid layer have been focused on a uniform heating of the fluid, the nonuniformity in the heat source has important implications for the temperature and flow fields, and the boundary heat fluxes. |
Monday, November 25, 2024 2:03PM - 2:16PM |
R32.00002: ABSTRACT WITHDRAWN
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Monday, November 25, 2024 2:16PM - 2:29PM |
R32.00003: Rayleigh–Darcy convection for the ultimate regime in three dimensions GARIMA VARSHNEY, Anikesh Pal We conduct direct numerical simulations (DNS) to reach the ultimate regime for Rayleigh-Darcy convection (RDC) in a three-dimensional domain. These simulations at large Rayleigh numbers (Ra) up to 1×106 are consistent with realistic Ra encountered in CO2 sequestration in deep saline aquifers (∼ O(Ra = 105 − 106)). The Nusselt number (Nu) and interior wave number (k) are used to analyze the ensuing heat transfer and flow dynamics. We find that the ratio Nu/Ra approaches a constant value for Ra > 5×105. Under the vigorous action of buoyancy for higher Ra, high-temperature fluid protrudes faster from the boundary and reaches the opposite boundary. These plumes further form large columnar structures which appear as bright ridges at the boundary. |
Monday, November 25, 2024 2:29PM - 2:42PM |
R32.00004: Free convection around human bodies with diverse shapes Shri H Viswanathan, Ankit Joshi, Isabella DeClair, Michael Park, Bryce Twidwell, Muhammad Abdullah, Konrad Rykaczewski Excessive indoor warmth can harm health and productivity, especially during heat waves or in buildings without air conditioning. Designing energy-efficient buildings that provide thermal comfort for diverse populations can reduce such negative health impacts, but it requires a quantitative understanding of the main heat exchange pathways—radiation and free convection—between humans and their indoor environment. Traditional methods to quantify these heat exchange pathways involved human subjects but were time-consuming and variable. Modern studies use physical or computational human models ("manikins"), but only when representing the shape of the "average" Western person. We address this gap by employing an experimentally validated numerical model to determine whole-body and regional free convection coefficients across diverse body shapes. We validate the simulations using a thermal manikin, ANDI, and simulate free convection around computational manikins representing the 1st to 99th percentile body mass index and height variations in U.S. adults. |
Monday, November 25, 2024 2:42PM - 2:55PM |
R32.00005: Investigating the Formation of Dust Devils through Linear Stability Analysis and Direct Numerical Simulations Jagmohan Singh Dust devils are organized vortical flows that arise from the interaction of buoyancy and circulation. While experimental investigations and numerical simulations have provided significant insights into their flow structure and dynamics, the exact conditions that trigger the formation of dust devils remain unclear. Although strong surface heating and circulation are known to be essential, the precise threshold values for these parameters are not well defined. |
Monday, November 25, 2024 2:55PM - 3:08PM |
R32.00006: Thermal and compositional driven convection generated by reaction fronts in Hele-Shaw cells or porous media Desiderio A Vasquez, Pablo M Vilela, Edwin A Llamoca Chemical reaction fronts propagating in liquids induced density gradients due to changes in chemical composition and temperature. These density gradients result in buoyancy driven instabilities for flat fronts propagating in the vertical direction. In this work, we analyze the conditions for instability for fronts propagating in Hele-Shaw cells or porous media. We modeled the front propagation using a reaction-diffusion-advection equation corresponding to cubic autocatalysis. The fluid motion is described using the Brinkman equation. We compare our results to solutions using the Navier-Stokes equation and Darcy's Law in the appropriate hydrodynamic limits. A linear stability analysis of a flat reaction-diffusion front shows good agreement to a thin front approximation based on an eikonal relation. This eikonal relation provides the normal front velocity as a function of its curvature. We show that for thermal driven convection, the flat front can be unstable even if the low-density fluid is above the high-density fluid. We solve the nonlinear equations for fluids confined in narrow two-dimensional domains. We observe transitions between different types of fronts propagating with constant velocity and steady curved shapes due to convection. |
Monday, November 25, 2024 3:08PM - 3:21PM |
R32.00007: Battery thermal performance evaluation with regular polygon arrangement under natural convection Congyu Mao, Hyun Wook Kang, HERNANDO EFRAIN LEON RODRIGUEZ, Kewei Gao, Woo Young Cho, Min Liang Wang Natural convection, being independent of additional power sources, is currently regarded as the most reliable method for dissipating heat. This study investigates the heat dissipation of Lithium-ion batteries under natural convection using different packaging methods and arrangements through simulation research. The results indicate that non-packaged battery modules demonstrate superior heat dissipation, while conventional packaging methods significantly influence heat dissipation. Moreover, the impact of packaging on heat dissipation varies with battery arrangement. A regular polygon based method is introduced here to represent the centrally symmetric arrangements for batteries. The results showed that the circular arrangement method is more conducive to the heat dissipation of the battery. Finally, the performance of battery modules is evaluated using volumetric effective energy after 500 cycles. The findings reveal that the non-packaged 4x4 array achieves the highest remaining volumetric effective energy at a 0.5C discharge rate, measuring 1.7 J/mm³, compared to 0.84 J/mm³ for the 3x3 array under identical conditions. |
Monday, November 25, 2024 3:21PM - 3:34PM |
R32.00008: Thermal impacts on wind-driven loads of solar PV modules Brooke J. Stanislawski, Ethan Young, Shashank Yellapantula Solar photovoltaic (PV) module life and performance can be negatively impacted by wind-driven structural loads. Characterizing and mitigating these wind-driven loads has become an active area of research, however, studies have not yet considered the influence of thermal conditions, which can vary temporally as ground, air, and module temperatures fluctuate. Using fluid-structure interaction simulations, we aim to quantify the sensitivity of PV module loads to the surrounding thermal conditions across a range of wind conditions. Findings are expected to inform PV plant operations to maximize module life and performance. |
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