Assessment of Reynolds Averaged Turbulence Models in Predicting Flow Structure Behind a Generic Automobile Body

Aerodynamic characteristics of a ground vehicle affect vehicle operation in many ways. Aerodynamic drag, lift and side forces have influence on fuel efficiency, vehicle top speed and acceleration performance. In addition, engine cooling, air conditioning, wind noise, visibility, stability and crosswind sensitivity are some other tasks for vehicle aerodynamics. All of these areas benefit from drag reduction and changing the lift force in favor of the operating conditions. This can be achieved by optimization of external body geometry and flow modification devices.

Majority of the aerodynamic drag force is generated on the rear side of a ground vehicle, therefore, the wake flow structure of a ground vehicle plays an important role in external aerodynamics. The present study investigates the wake flow structure behind a generic ground vehicle (Ahmed body). The flow field analysis is performed by solving three-dimensional Reynolds Averaged Navier-Stokes equation in finite volume approach. Accuracy of RANS calculations is investigated to obtain the correct representation of the wake flow behind the body. Numerical calculations are performed for 25-degree backlight angle, and the results are compared with each other and experiments.