Simulation Considerations for Commercial Vehicles in Strong Crosswind Conditions

Aerodynamic testing of heavy commercial vehicles is of increasing interest as demands for dramatically improved fuel economy take hold. Various challenges which compromise the fidelity of wind tunnel simulations must be overcome in order for the full potential of sophisticated aerodynamic treatments to be realized; three are addressed herein. First, a limited number of wind tunnels are available for testing of this class of vehicle at large scales. The authors suggest that facilities developed for large or full-scale testing of race cars may be an important resource. Second, ground simulation in wind tunnels has led to the development of Moving Ground Plane (MGP, aka Rolling Road (RR)) systems of various types. Questions arise as to the behavior of MGP/RR systems with vehicles at large yaw angles. It can actually be deduced that complete simulation of crosswind conditions on an open road in a wind tunnel may be impractical. This is due to the fact that the atmospheric crosswind develops a deep boundary layer profile, such that the resultant inflow seen by the moving vehicle is effectively curved. Finally, prevailing methods of boundary corrections for automotive testing have focused largely on drag, with reasonably symmetric flow fields. Relatively long vehicles at large yaw angles develop highly asymmetric flow fields, so more complex boundary correction methods need to be developed. Although computational simulation of real-world conditions (i.e. with crosswind) may seem to be a little easier, various options need to be carefully explored for best results.