Chen, M., Mokhtar, W., Britcher, C., and McGarry, J., "Experimental and Computational Aspects of Ground Simulation for Vehicles in Strong Crosswind Conditions," SAE Technical Paper 2014-01-0588, 2014, doi:10.4271/2014-01-0588.
The issue of ground simulation in wind tunnels has led to the development of Moving Ground Plane (MGP, aka rolling road) systems of various types. Motorsports aerodynamics has perhaps been the primary application to date, where the range of vehicle yaw angles tends to be quite limited. In fact, since yaw angles are typically developed as result of vehicle slip in cornering, or asymmetric set-up in the case of stock cars, they are limited to a few degrees. Further, since in both cases the vehicle centerline typically rotates with respect to the relative velocity vector (i.e. simulating vehicle slip in cornering), it seems clear that yawing the vehicle in the wind tunnel above a fixed (non-rotated) MGP is a valid simulation option. In the case of vehicles operating in strong crosswind conditions, for example commercial vehicles (heavy trucks) on interstate highways, the situation is more complex. The crosswind develops a deep boundary layer profile, such that the resultant inflow seen by the moving vehicle is effectively curved. In the wind tunnel, high fidelity simulation of this curved inflow is effectively impossible and the question arises as to what aerodynamic simulation is acceptably close to real-world conditions, particularly if a MGP is in use. Computational simulation of real-world conditions is a little easier, but various options need to be explored for best results.