Abstract
Large-eddy simulation (LES) of separated turbulent flow through an asymmetric plane diffuser is investigated. The outcome of an actual LES depends on the quality of the subgrid-scale (SGS) model, as well as the accuracy of the numerical method used to solve the equations for the resolved scales. In this paper, we focus on the influence of SGS models for LES of the diffuser flow through using a high-order finite difference method to solve the equations for the resolved scales. Six resolutions are computed to investigate the influence of mesh resolution. Four existing SGS models, a new one-equation dynamic SGS model and a direct numerical simulation (DNS) are conducted in the diffuser flow. A series of computational analyses is performed to assess the performance of different SGS models on the coarse grids. By comparison with the experiment and DNS, the results produced by the new one-equation dynamic model give better agreement with experiment and DNS than the four other existing SGS models.
Highlights
We focus on the influence of SGS models for Large-eddy simulation (LES) of the separated turbulent flow in an asymmetric diffuser on the relative coarse mesh through using a high-order finite difference method to solve the equations for the resolved scales
To allow a good comparison of simulation results and experimental measurements, the data associated with vertical cross-sections x/H = 9.2, 15.2, 19.2 and 25.2 in the spatially-developing region, which match the location used in previous experiments, are combined into one plot
Six resolutions were conducted for investigating the influence of mesh resolution in the turbulent diffuser flow
Summary
They serve to increase the static pressure of a flow by reducing its velocity, albeit often with significant losses. It has a simple design, but it develops complex three-dimensional flow features. Because of its simple three-dimensional geometry and the existence of a high quality velocity dataset, this diffuser has become a popular test case for measurement of mild separation and validating numerical simulations. In a numerical simulation of the diffuser, the presence of an adverse pressure gradient and the formation of an unsteady separation bubble make this flow very sensitive and difficult to predict with numerical means
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