Large Eddy simulation of tracer gas dispersion in a cavity

Abstract

This paper assesses the prediction of inert tracer gas dispersion within a cavity of height (H) 1.0 m, and unity aspect ratio, using large Eddy simulation (LES). The flow Reynolds number was 67 000, based on the freestream velocity and cavity height. The flow upstream of the cavity was laminar, producing a cavity shear layer which underwent a transition to turbulence over the cavity. Three distinct meshes are used, with grid spacings of (coarse), (intermediate), and (fine) respectively. The Smagorinsky, WALE, and Germano-Lilly subgrid-scale models are used on each grid to quantify the effects of subgrid-scale modelling on the simulated flow. Coarsening the grid led to small changes in the predicted velocity field, and to substantial over-prediction of the tracer gas concentration statistics. Quantitative metric analysis of the tracer gas statistics showed that the coarse grid simulations yielded results outside of acceptable tolerances, while the intermediate and fine grids produced acceptable output. Interrogation of the fluid dynamics present in each simulation showed that the evolution of the cavity shear layer is heavily influenced by the grid and subgrid scale model. On the coarse and intermediate grids the development of the shear layer is delayed, inhibiting the entrainment and mixing of the tracer gas into the shear layer, reducing the removal of the tracer gas from the cavity. On the fine grid, the shear layer developed more rapidly, resulting in enhanced removal of the tracer gas from the cavity. Concentration probability density functions showed that the fine grid simulations accurately predicted the range, and the most probable value, of the tracer gas concentration towards both walls of the cavity. The results presented in this paper show that the WALE and Germano-Lilly models may be advantageous over the standard Smagorinsky model for simulations of pollutant dispersion in the urban environment.

Publication DOI: https://doi.org/10.1088/1873-7005/ac421b
Divisions: College of Engineering & Physical Sciences > School of Computer Science and Digital Technologies
College of Engineering & Physical Sciences > School of Computer Science and Digital Technologies > Software Engineering & Cybersecurity
College of Engineering & Physical Sciences > Aston Fluids Group
Aston University (General)
Funding Information: This research was performed on ALICE2, the University of Leicester High Performance Computing Service. The research was supported through a Royal Academy of Engineering / Leverhulme Trust Research Fellowship, Grant No. LTRF1920\16\38.
Additional Information: Copyright © 2022 The Japan Society of Fluid Mechanics and IOP Publishing Ltd. Original Content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Uncontrolled Keywords: large Eddy simulation,tracer gas dispersion,vortices,Mechanical Engineering,General Physics and Astronomy,Fluid Flow and Transfer Processes
Publication ISSN: 1873-7005
Last Modified: 01 May 2025 08:44
Date Deposited: 30 Apr 2025 11:13
Full Text Link:
Related URLs: https://iopscie ... 873-7005/ac421b (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2022-01-14
Accepted Date: 2021-12-10
Authors: McMullan, W. A. (ORCID Profile 0000-0001-7253-8449)

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