Abstract
In order to improve the limitation of steady-state automobile aerodynamic lift characteristics in finite volume method, the Lattice Boltzmann Method (LBM) was conducted on transient simulation of automobile aerodynamic lift. This proposed method utilized adaptive wake refinement feature to obtain a series of regular fluid particles for macroscopic fluid and combined large eddy simulation (LES) with wale-viscosity model to study the transient characteristics of automobile aerodynamic lift. In this numerical investigation, using the international standard automobile MIRA model, the temporal and spatial characteristics of rear velocity field and vorticity field were analyzed, whose results had agreement with the wind tunnel test data. It was showed that the elaborate information of flow field around the car-body and the aerodynamic lift could be more accurately described. A pair of asymmetric non-periodical and inward twisting rear vortexes in the car rear flow field was found, while it squeezed and dragged each other in different eddy scales. This result also indicated the aerodynamic lift to oscillate in a certain amplitude scope, markedly different from the simulated result of steady state automobile aerodynamic lift, which is more close to real driving conditions. DOI: http://dx.doi.org/10.5755/j01.mech.23.6.19847
Highlights
In order to save fuel, reduction of aerodynamic drag has always been concerned by car-body design engineer, but little attention was paid to aerodynamic lift
In terms of automobile aerodynamic lift being proportional to the second-order of speed, the reduction of tire gripping capacity could be caused by the increasing speed, which would bring the vehicle handling and stability problems
Based on the theory of the aircraft aerodynamic lift, the steady-state theory of automobile aerodynamic lift suggests that the air flowing velocity through the upper is faster than the bottom because the upper surface of car-body is longer than the bottom surface
Summary
In order to save fuel, reduction of aerodynamic drag has always been concerned by car-body design engineer, but little attention was paid to aerodynamic lift. For many years the attention of automobile aerodynamic lift is devoted largely to steady state, while the transient characteristics research is rarely presented. Based on the theory of the aircraft aerodynamic lift, the steady-state theory of automobile aerodynamic lift suggests that the air flowing velocity through the upper is faster than the bottom because the upper surface of car-body is longer than the bottom surface. It is believed that the pressure difference between the upper and the bottom surface brings about the aerodynamic lift [1]. Due to the phenomena of the ground effects, the aerodynamic lift of some car-body models is negative, which implies the 2D path steady-state theory is insufficient to explain the real situation
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