CFD Approach to Evaluate Wind-Tunnel and Model Setup Effects on Aerodynamic Drag and Lift for Detailed Vehicles 2010-01-0760

Previous work by the authors showed the development of an aerodynamic CFD model using the Lattice Boltzmann Method for simulating vehicles inside the IVK Model-Scale Wind-Tunnel test-section. In both experiment and simulation, alternate configurations of the wind-tunnel geometry were studied to change the pressure distribution in the wind-tunnel test section, inducing a reduction in aerodynamic drag due to interference between the wind-tunnel geometry and the pressure on the surface of the vehicle. The wind-tunnel pressure distribution was modified by adding so-called “stagnation bodies” inside the collector to create blockage and to increase the pressure in the rear portion of the test section. The primary purpose of previous work was to provide a validated CFD approach for modeling wind-tunnel interference effects, so that these effects can be understood and accounted for when designing vehicles.

In this paper, the study using this CFD approach is extended to a broader range of effects of the wind-tunnel and model setup on the aerodynamic drag and lift. The effects of three different wind-tunnel pressure distributions are shown for detailed sedan and SUV models, presenting the interaction between vehicle shape and wind-tunnel interference effects. Additional effects were investigated, including the vehicle ride height and details in the geometry of the underbody.

Secondly, the possibility to apply standard wind-tunnel correction methods to the current data was examined for both vehicles. Corrections for wind-tunnel pressure gradient and open-jet wind-tunnel nozzle and collector blockage were applied to the data. In the simulation, the effect of wind-tunnel interference on the vehicle was examined by comparing to simulation with no wind-tunnel geometry and negligible blockage. Ideally, the corrected wind-tunnel data and the simulation with negligible blockage should match closely.

In summary, this paper provides a good foundation for using aerodynamic simulation to explore the various effects in a wind-tunnel, and provide a needed connection between wind-tunnel data and on-road performance.