Wind tunnel tests on drag reduction of heavy vehicles using sinusoidal boat tails

A sinusoidal boat tail (SBT) is developed and investigated to greatly reduce drag, side force, and yawing moment under crosswind conditions. The drag and side forces of a heavy vehicle model with the SBT are reduced by 15.9 % and 22.6 %, respectively, relative to those of a reference model without the SBT at a yaw angle of 7 degrees. Therefore, the SBT improves the aerodynamic performance and driving stability of the vehicle model. Flow characteristics around the vehicle model are measured using a particle image velocimetry technique. Mean velocity field results show that the SBT effectively suppresses the formation of longitudinal vortices by enhancing the streamwise velocity of the region behind the boat tail. In addition, the streamwise momentum deficit is reduced in the wake region owing to the development of a secondary recirculating flow region.