Aerodynamic Characteristics of Mira Fastback Model in Experiment and CFD

摘要

The lasting high fuel cost has recently inspired the resurgence in drag reduction research for vehicles, which calls for a thorough understanding of the vehicle wake. The acknowledged MIRA fastback vehicle model is characterized by similar real vehicle geometry, thus it is especially suitable for the above purpose. In spite of a considerable number of previous investigations, our knowledge of flow around this model remains incomplete. This paper aims to visit turbulent flow structure behind this model. An investigation has been conducted to measure the near wake flow structure of the MIRA 1/8 scale mode, using both Particle Image Velocimetry (PIV) experimental method and Computational Fluid Dynamics (CFD) simulation method. In order to capture the flow structure accurately, PIV measurement was performed in different sections along three orthogonal directions, and the CFD method acquired additional simulation results to catch the better flow status. Through the maps of the time-averaged vorticity, the instantaneous vorticity and the handled velocity vector from the PIV and CFD methods, we found out the formation mechanism of the transient flow of fastback model and summed up the schematic of flow structure. This study not only analyzed the vortex shedding characteristics of turbulent near wake, but more importantly provided insight into the complex three-dimensional features of the flow structure in the wakes of MIRA fastback model.