2017/11/03 by Jahrul Alam, Alam, Jahrul M, Luke P. J. Fitzpatrick +1
Earth and Planetary Sciences · Engineering · Environmental Science · #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Turbulent Flows #Meteorological Phenomena and Simulations #Wind and Air Flow Studies
paper · pdf · doi:10.48550/arxiv.1711.01373
openalex publication_date 2017/11/03 · openalex created_date 2022/09/15 · openalex updated_date 2026/07/28
Large-eddy simulation (LES) of a turbulent flow through an array of\nbuilding-like obstacles is an idealized model to study transport of\ncontaminants in the urban atmospheric boundary layer (UABL). A reasonably\naccurate LES prediction of turbulence in such an UABL must resolve a\nsignificant proportion of the small but energetic eddies in the roughness\nsublayer, which remains prohibitive even though computational power has been\nincreased significantly. In this article, we present a large-eddy simulation\nmethodology to study turbulence in UABLs, where the turbulence closure is based\non coupling the eddy viscosity method with the canopy stress method. Unlike the\nclassical Smagorinsky model that considers only the strain portion of the\nvelocity gradient tensor, we consider both the strain tensor and the rotation\ntensor to compute the eddy viscosity. This allows us to dynamically adapt the\nrate of energy dissipation to the scales of the energetic eddies in the\nroughness sublayer. Without employing a mesh conforming to the urban roughness\nelements, the effect of such solid bodies are represented in the LES model\nthrough a canopy stress method in which the loss of pressure and the sink of\nmomentum due to the interaction between eddies and roughness elements are\nparameterized using the instantaneous velocity field. Simulation results of the\nproposed canopy stress method is compared with that of a conventional\nComputational Fluid Dynamics (CFD) method employing a block-structured mesh\nconforming around the roughness elements. For urban flow simulations, the\nresults demonstrate that the proposed canopy stress model is accurate in\npredicting vertical profiles of mean and variance, as well as the temporal\nintermittency of coherent structures.\n