Airfoil Plan-View Body Shapes to Reduce Drag at Yaw

In the presence of ambient winds, almost all present vehicles experience an increase in aerodynamic drag, which in turn causes an increase in energy consumption. However, it is possible to design a vehicle body shape that passively uses the wind to decrease aerodynamic drag and hence lower fuel consumption. This paper describes a scale-model wind tunnel investigation that studied vehicle-like shapes which exhibit a drag reduction, rather than a drag penalty, in crosswinds. The aerodynamic behavior of very-low-aspect-ratio, truncated, vertical airfoil sections close to the ground was studied to obtain a general idea of the behavior of these vehicle-like shapes. Force and surface pressure studies established that a significant drag reduction at low yaw angles could be achieved by attached flow over the leeward airfoil nose. A demonstration of the use of the airfoil shape was carried out to show how the poor yaw performance of a representative Semi-Trailer transport may be improved by the use of a plan-view airfoil-shaped cab.