Abstract: The ground effect is one of the main difficulties in road vehicle aerodynamics. A model of ground effect is put forward using wall function theory and close wall effect of moving ground to turbulent flow on the basis of vehicle relative motion to the ground. In the calculation of flow field around some caravan model，three-dimensional unsteady Navier-Stokes equations are solved by choosing RNG K–e model equations. The result gives the conclusion that the drag coefficient (Cd) of the vehicle model increases and the lift coefficient (Cl) doesn’t change monotonously as the ground clearance is increased within a standard range. It coincides well with the experiment result on which moving-model technique is applied. Whereas the error of the result will increase obviously on the basis of stationary ground.

Key words: Aerodynamics, Automotive, CFD, Ground effect