Correlation Experience with the SAE Wind Tunnel Test Procedure for Trucks and Buses

Six-component aerodynamic force and moment data are compared from tests of four 1/10-scale truck models at four wind tunnels on the North American Continent. Each model was tested in both a standard and a fuel saver configuration.

The differences observed between tunnels were consistent for each aerodynamic component regardless of truck or configuration. The zero-yaw drag coefficients from each of the four tunnels were within ± 4 percent of the mean coefficients. The coefficient magnitudes for the other aerodynamic components showed variations that were often many times larger than those for drag. The variations between the incremental coefficients for all six aerodynamic components were less than those found for the coefficient magnitudes. A qualified comparison was made between the average drag coefficient magnitudes from the wind tunnels and those available from some on-road coastdown tests of the full-scale vehicles.