Numerical and experimental study of two-vehicle overtaking process

Abstract

The overtaking process between two simplified Ahmed body models is studied using a set of static experiments to provide a comparison basis for the numerical study. Both steady-state (static) and transient (dynamic) simulations are performed. There are notable differences of the drag and side force coefficients between the predicted and experimental results in the wake effects on the overtaking model as well as under a situation when two models are parallel for the static tests. These differences are attributed to the SST k − ω model, which is a two-equation Reynolds-averaged Navier-Stokes equation (RANS) turbulence model with an assumption of isotropic eddy viscosity, employed in the simulation. A more advanced turbulence model that simulates large-eddy organized motion in a turbulent flow and which uses an anisotropic eddy viscosity formulation in the near-wall flow subregion would increase the prediction accuracy for the overtaking simulation. A comparison of the results for the steady-state and the transient simulations at various relative velocity ratios ( r ) shows that the quasi-steady approach is suited to simulate the dynamic two-vehicle overtaking process when the condition r ≤ 0 . 1 is met.