A Wide Belt Correction Strategy for Belt-Whip and Wheel Ventilation Drag

The increased importance of aerodynamics to help with overall vehicle efficiency necessitates a desire to improve the accuracy of the measuring methods. To help with that goal, this paper will provide a method for correcting belt-whip and wheel ventilation drag on single and 3-belt wind tunnels. This is primarily done through a method of analyzing rolling-road only speed sweeps but also physically implementing a barrier. When understanding the aerodynamic forces applied to a vehicle in a wind tunnel, the goal is to isolate only those forces that it would see in the real world. This primarily means removing the weight of the vehicle from the vertical force and the rolling resistance of the tires and bearings from the longitudinal force. This is traditionally done by subtracting the no-wind forces from the wind at testing velocity forces. The first issue with the traditional method is that a boundary layer builds up on the belt(s), which can then influence a force onto the vehicle’s undercarriage. The wheels and tires impart energy into the air relative to the velocity they rotate, typically called pumping-losses or ventilation-drag. These pumping-losses will be measured in the no-wind condition and subsequently subtracted out in the traditional method. This paper will cover methods for eliminating or reducing these effects and covering the consequences of doing so. It will start by going into the effects of using solid tires in reduced-scale model testing. Then it will explore expanding upon that for full vehicles using traditional pneumatic tires. In doing so, we will cover breaking out belt-whip and wheel pumping-losses. This paper will also cover some example results and suggested next steps.