Effect of Local Grid Refinement on Performance of Scale-Resolving Models for Simulation of Complex External Flows

Amne Elcheikh,Michel Elkhoury

doi:10.3390/aerospace6080086

Abstract

Numerical simulations are crucial for fast and accurate estimations of the flow characteristics in many engineering applications such as atmospheric boundary layers around buildings, external aerodynamics around vehicles, and pollutant dispersion. In the simulation of flow over urban-like obstacles, it is crucial to accurately resolve the flow characteristics with reasonable computational cost. Therefore, Large Eddy Simulations on non-uniform grids are usually employed. However, an undesirable accumulation of energy at grid-refinement interfaces was observed in previous studies using non-uniform grids. This phenomenon induced oscillations in the spanwise velocity component, mainly on fine-to-coarse grid interfaces. In this study, the two challenging test cases of flow over urban-like cubes and flow over a 3-D circular cylinder were simulated using three different scale-resolving turbulence models. Simulations were performed on uniform coarse and fine grids on one hand, and a non-uniform grid on the other, to assess the effect of mesh density and mesh interfaces on the models’ performance. Overall, the proposed One-Equation Scale-Adaptive Simulation (One-Equation SAS) showed the least deviation from the experimental results in both tested cases and on all grid sizes and types when compared to the Shear Stress Transport-Improved Delayed Detached Eddy Simulation (IDDES) and the Algebraic Wall-Modeled Large Eddy Simulation (WMLES).

Highlights

Accurate predictions of flow fields are essential in designing complex engineering configurations.Computational fluid dynamics is a powerful and time-saving tool to visualize and estimate the properties of internal flows and external aerodynamics
Three turbulence models that belong to the closure family, i.e., algebraic, one-equation and two-equation models, were examined over two globally unstable test cases that involved massive flow separation
Unlike the Wall-Modeled Large Eddy Simulation (WMLES) and the Improved Delayed Detached Eddy Simulation (IDDES), which depend on the grid scale, the proposed

Summary

Introduction

Accurate predictions of flow fields are essential in designing complex engineering configurations.Computational fluid dynamics is a powerful and time-saving tool to visualize and estimate the properties of internal flows and external aerodynamics. Accurate predictions of flow fields are essential in designing complex engineering configurations. One important external flow scenario that is gaining remarkable interest is wind flow around buildings. Wind generates loads on the building envelop and plays an important role in the transport of contaminants. For efficient building design and maintaining desired air quality, accuracy in predicting flow characteristics is crucial. Simplified cases of flow around buildings consisting of three-dimensional flow around cubes with in-line or staggered configurations have been extensively covered in the literature [1,2,3,4,5,6,7,8,9,10]. More complex geometries were used to simulate real building outer profiles [11,12,13,14,15]. Lateb et al [16]

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Conclusion