Aspects on Numerical Simulation of Overtaking Process between Two Vehicles

Two aspects of the numerical simulation of the overtaking process between two vehicles are investigated in the study. One is the search for a reliable and yet economical turbulence model in such simulation. The other is how to set up the proper inlet and outlet boundaries of a computational domain in the simulation subject to a situation that the assumed inlet and outlet conditions have to be employed. The overtaking process between two simplified Ahmed body models at the moment with zero distance, counting from the back surface of the overtaken model to the front surface of the overtaking model, is considered to investigate these two aspects. Experiments are also conducted to provide the measured information for performing the study. In consideration of both prediction accuracy and computational cost in such simulation problem, the SST k-ω turbulence model possessing the capability to predict near-wall flow behaviors well with a proper design of near-wall grid mesh is recommended. Set up of a sufficient large stream-wise (x) computational domain in the simulation using the assumed inlet and outlet conditions should follow the criteria of the inlet and outlet boundaries being placed at least 7l upstream distance (here l denotes the length of the vehicle) in front of the leading vehicle and at least 8l downstream distance behind the lagging one to assure the correctness of simulation results.