Some Principles of Automotive Aerodynamic Testing in Wind Tunnels with Examples from Slotted Wall Test Section Facilities

The various factors related to obtaining high quality data from automotive aerodynamic wind tunnel tests are outlined. These factors can be subdivided into the test section flow quality, testing procedures, and the influence of the test section boundaries. Methods of achieving and measuring the test section flow quality necessary for typical road vehicles are discussed. The benefits of using a slotted wall test section configuration to reduce blockage interference effects are illustrated. Examples are drawn from measurements of flow quality and from force/moment comparison model tests in 1/4 and 1/5 scale pilot slotted wall wind tunnels. Finally, standards of flow quality and standardized testing procedures are proposed for automotive testing to allow proper comparison of test data obtained in different wind tunnels.