Assessment of Computational Fluid Dynamics Reynolds-Averaged Navier–Stokes Models for Bluff Bodies Aerodynamics

Abstract

<div>Since the steady-state computational fluid dynamics (CFD) Reynolds-averaged Navier–Stokes (RANS) turbulence models offer low-cost and sensible accuracy, they are frequently utilized for bluff bodies’ external aerodynamics investigations (e.g., upwind, crosswind, and shape optimization). However, no firm certainty is made regarding the best model in terms of accuracy and cost. Based on cost and accuracy aspects, four RANS turbulence models were studied, which are Spalart–Allmaras, realizable k-ε, RNG k-ε, and SST k-ω. Ahmed body with a 25° slant angle benchmark case was introduced for this investigation. Two grids were generated to satisfy the near-wall treatment of each turbulence model. All grid settings were proposed and discussed in detail. Fluid-structure analysis was performed on five different planes. Regarding flow field prediction, realizable k-ε and renormalization group (RNG) k-ε models demonstrated a remarkable consistency with experimental data, while Menter’s shear stress transport (SST) k-ω showed a poor agreement. The obtained computational values of drag and lift coefficients were compared with experimental results. All investigated RANS turbulence models had reported results in excellent agreement with experimental drag coefficient values. The SST k-ω model has underestimated lift coefficient value with an error of about −45% with experimental value. Only realizable k-ε and RNG k-ε presented an error <10% for predicting drag and lift coefficients.</div>