해치백 차량에서 리어 스포일러의 공력성능에 대한 연구

Aerodynamic effects of rear spoiler for hatch back vehicle are investigated using full scale wind tunnel (WT) test and computational fluid dynamics(CFD). S2A WT located in St-Cyr, France, and commercial CFD program based on Lattice Boltzmann Method(LBM) are used for WT test and CFD analysis, respectively. Three rear spoilers were tested with respect to the lateral design and it is shown that aerodynamic drag reduction is from 30 drag count to 90 drag count (1 drag count = 0.001 ㎡) in addition to the reduction of rear lift. For the accurate analysis of underbody flow, rotating wheel and moving ground is implemented. Difference of CdA with and without rear spoiler is compared between WT test and CFD and it is shown that current CFD technique can accurately predict the effect of rear spoiler in terms of CdA. Rear spoiler decreases Coanda effect at the rear wind shield, so that flow passing through underbody is increased and these results in balanced wake and the reduction of depression area at the rear wind shield.