关键词: 非定常来流, 汽车外流场, 气动升力, 瞬态特性

Abstract:

An approach of combining the large eddy simulation and wind tunnel experiment was employed to study the variation of transient characteristics of automotive aerodynamic lift under the unsteady stream.The effects of velocity perturbation frequencies on aerodynamic lift were analyzed and the physical mechanism contributing to the variation on the aerodynamic characteristics was discussed. Simulation results show that velocity perturbation frequencies have a great impact on lift coefficient.Specifically, in terms of short period oscillating stream, lift coefficient changes in accordance with sinusoidal curve. With respect to the long period oscillating stream, however, lift coefficient firstly increases and then decreases. Finally, it tends to stable oscillation. The primary analysis shows that trail flow field structure largely affects the magnitude and direction of the aerodynamic lift. Additionally, the change of velocity perturbation leads to the change of pressure difference between upper and lower of the body, thereby giving rise to the change of aerodynamic lift.

Key words: unsteady stream, flow field around vehicle, aerodynamic lift, transient characteristics