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 R16: CFD: LES, DNS, Hybrid RANS/LES I |
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Chair: Huidan (Whitney) Yu, Purdue University Room: 155 F |
Monday, November 25, 2024 1:50PM - 2:03PM |
R16.00001: Turbulence heat transport by Prandtl's secondary flows and Kelvin-Helmholtz instabilities Adnan Masruf Abir, Todd Harman, Raúl Bayoán B Cal, Marc Calaf Prandtl's secondary flow of the second kind, also known as stress-induced secondary flow, arises from the anisotropy of Reynolds stress terms. This phenomenon is typically generated by spanwise heterogeneous surfaces, resulting in secondary flow in the form of counter rotating streamwise vortices. Extensive research has analyzed this type of secondary flow under various roughness types, spacings, and widths. Recently, a few studies have investigated the effect of anisotropic buoyancy on secondary flow using streamwise-aligned, alternately heated smooth patches. However, the combined effect of heterogeneous spanwise roughness and anisotropic buoyancy remains largely unexplored. In this study, Large Eddy Simulations (LES) of streamwise-aligned, heated bluff objects will be conducted to investigate how secondary flow of the second kind influences heat transfer. The results will be compared with heat transfer induced by Kelvin-Helmholtz instability-triggered spanwise rollers, generated by spanwise-aligned heated bluff objects. |
Monday, November 25, 2024 2:03PM - 2:16PM |
R16.00002: Large eddy simulation of a utility-scale vertical-axis marine hydrokinetic turbine under mobile bed conditions Mehrshad Gholami Anjiraki, Hossein Seyedzadeh, Mustafa Meriç Aksen, Christian Santoni, Kevin Flora, Ali Khosronejad We present a coupled large-eddy simulation (LES) and bed morphodynamics study to explore the impact of mobile bed flume and sediment dynamics on the performance of a utility-scale vertical-axis marine hydrokinetic turbine (VAT). This study also aims to gain insight into the impact of the VAT wake flow on the sediment dynamics and scour development in the waterways, thus addressing the environmental impact of such turbines. To that end, we analyzed the wake recovery, power production, and sediment dynamics of the system at various tip speed rations. Various components of the turbine, waterway, and sediment layer are captured using the geometry-resolving immersed boundary method. The findings of the study revealed the intricate turbulent wake flow field of the VAT and its footprint on the mobile bed in the form of 3D sand waves throughout the channel bed. |
Monday, November 25, 2024 2:16PM - 2:29PM |
R16.00003: Dynamics of Buoyancy-Driven Exchange Flow over an Obstacle Sanaz Izadifar Buoyancy-driven exchange flows arise in the natural and built environment wherever bodies of fluids at different densities are connected by a narrow constriction, and two layers of fluids have enough momentum to develop a strong shear-layer at the interface. This often leads to complex flow and mixing patterns. A prime example of this flow observed between the North and South sides of the Great Salt Lake (GSL), Utah. Recent seminal experimental research on this class of flows by Lefauve and Linden [1,2] and complementary numerical study [3] has quantified the turbulent structures of the flow at mixing interface. The current study, inspired by the obstacle hindered flows between the North and South sides of the flow observed at the GSL [4], quantifies the effect of a rectangular obstacle on the dynamics of the flow. The results will focus on the steady-state long-term dynamics at the mixing interface, investigating the effect of the obstacle and the impact of Reynolds number and densimetric Froude number on the mixing dynamics. The study will use direct numerical simulations (DNS) of the governing equations under the Boussinesq approximation, solved using high-order spectral element method. |
Monday, November 25, 2024 2:29PM - 2:42PM |
R16.00004: A RANS-RSM based Eddy-Resolving Modeling of Bubble Plume Dynamics in Water Reservoirs and Channels Suad Z Jakirlic, Ivan Joksimovic Bubble plumes released into a quiescent water in a vertical reservoir and into a water cross-flow in a horizontal duct, both with rectangular cross sections, are computationally simulated within the Euler-Lagrange framework for two-phase flow computations. The described gas-liquid flow cases are characterized by a number of strongly coupled phenomena, such as bubble jet propagation, free surface flow, turbulence anisotropy induced secondary motion, and the varying interaction dynamics of the continuous water environment with the bubble dispersion. An appropriately extended differential near-wall Reynolds stress model in conjunction with a two-way coupled Euler-Lagrange approach describes the dynamics of unresolved subscale structures within the Sensitized Reynolds-Averaged Navier-Stokes (RANS) modeling strategy. The work focuses on assessing the predictive performance of this eddy-resolving turbulence model by comparing the computational results with existing reference studies and analyzing the accuracy of the time-averaged flow topology and associated turbulence structures. The study of the dynamic properties of the instantaneous character of the flow using the proper orthogonal decomposition reveals large-scale transient effects associated with the bubble jet. |
Monday, November 25, 2024 2:42PM - 2:55PM |
R16.00005: Bubble Size Distribution in Decaying High Turbulence usingPopulation Balance Equation Ardalan Javadi, Vivek Kumar, Cyrus K Aidun The population Balance equation (PBE) employed with Euler-Euler formulation available in Open- |
Monday, November 25, 2024 2:55PM - 3:08PM |
R16.00006: Large Eddy Simulation of Ducted Propeller Tip Vortex Interactions with Application to Cavitation Inception Theo J Leasca, Krishnan Mahesh, Thomas Kroll Large-Eddy Simulation (LES) is performed to study the tip vortex flow in a ducted marine propulsor geometry replicating the experiments of Chesnakas and Jessup (ASME FEDSM 2003) and Oweis et al. (J. Fluids. Eng. 2006). Inception of cavitation in these marine propulsion systems is closely tied to the unsteady interactions between multiple vortices in the tip region. LES is used to shed insight into the structure of the tip vortex flow across a range of operating conditions. Simulation results are able to predict propeller loads within experimental scatter and show agreement with LDV measurements of the mean flow in the blade wake at design advance ratio, J = 0.98. |
Monday, November 25, 2024 3:08PM - 3:21PM |
R16.00007: Flow over Ice Roughness Patch Tianyi Li, Xiaohan Hu, Xiang Yang, Rahul Agrawal, Federico Zabaleta, Brett Bornhoft This talk reports a DNS dataset of flow over rime and glaze ice roughness and their modeling in the context of Reynolds-averaged Navier-Stokes (RANS) and wall-modeled large-eddy simulation (WMLES). The flow configuration is a channel, with the inflow generated from a plane-channel precursor. The ice roughness patch comes from scans of realistic icing on airfoils, and the roughness height is set to be about 1/6 of the half-channel height. The DNS results show that the mean flow is largely parallel and that the dispersive stress is negligible outside the ice roughness. A delayed response is observed in the Reynolds stress, but the mean flow seems to attain equilibrium rapidly irrespective of the type of ice roughness. Encouraged by these observations, we invoke equilibrium-type modeling assumptions. Specifically, we formulate a mixing length model to close the RANS equations and adopt the equilibrium rough-wall model for LES wall modeling. Both models require equivalent roughness height information, which can be obtained through roughness correlations using morphological parameters as inputs. In this study, two correlations by Bornhoft et al. and Flack & Schultz are considered and applied locally to account for the streamwise variation of the ice roughness. Both the RANS and WMLES results are promising, capturing, to some extent, the streamwise variation of the skin friction in the flow. In summary, we conclude the following: Firstly, we do not observe a strong history effect in the mean flow—at least for the roughness patches and length scales considered here. Secondly, equilibrium-type models provide reasonable skin friction predictions—again, at least for the roughness and length scales considered here. |
Monday, November 25, 2024 3:21PM - 3:34PM |
R16.00008: Fluid Mechanics-Informed Statistical Optimization of Spatial Configurations to Minimize Airborne Disease Transmission in Indoor Spaces Rupal Patel, Sivaramakrishnan Balachandar, Nadim Zgheib, Kalivelampatti Arumugam Krishnaprasad
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