Computational Fluid Dynamics Study of Separated Flow Over a Three-Dimensional Axisymmetric Hill

Abstract

This paper investigates the ability of computational fluid dynamics (CFD) simulations to accurately predict the turbulent flow separating from a three-dimensional (3D) axisymmetric hill using a recently developed four-equation eddy-viscosity model (EVM). The four-equation model, denoted as k–kL–ω–v2, was developed to demonstrate physically accurate responses to flow transition, streamline curvature, and system rotation effects. The model was previously tested on several two-dimensional cases with results showing improvement in predictions when compared to other popularly available EVMs. In this paper, we present a more complex 3D application of the model. The test case is turbulent boundary layer flow with thickness δ over a hill of height 2δ mounted in an enclosed channel. The flow Reynolds number based on the hill height (ReH) is 1.3 × 105. For validation purposes, CFD simulation results obtained using the k–kL–ω–v2 model are compared with two other Reynolds-averaged Navier–Stokes (RANS) models (fully turbulent shear stress transport k–ω and transition-sensitive k–kL–ω) and with experimental data. Results obtained from the simulations in terms of mean flow statistics, pressure distribution, and turbulence characteristics are presented and discussed in detail. The results indicate that both the complex physics of flow transition and streamline curvature should be taken into account to significantly improve RANS-based CFD predictions for applications involving blunt or curved bodies in a low Re turbulent regime.

Assessment of RANS turbulence closure models for predicting airflow in neutral ABL over hilly terrain

“…Carrying out CFD simulation of the ABL has been the subject of many studies: complex terrain [7,8], pollutant dispersion [9,10], wind load on turbines buildings [11] and urban environment [12]. In particular many studies have been examined by several research groups for studying the turbulent airflow around hill (i.e., [13,14,23,24,[15][16][17][18][19][20][21][22]). Most of these works have emphasized the severe limitation resulting from the size of the problem yielded by the necessity to discretize the unbounded ABL domain, which increases considerably the demand on computing capacity.…”