Turbulence is known to influence the aerodynamic and aeroacoustic performance of ground vehicles. What is not thoroughly understood are the characteristics of turbulence that influence this performance and how they can be applied in a consistent manner for aerodynamic design and evaluation purposes. Through collaboration between Transport Canada and the National Research Council Canada (NRC), a project was undertaken to develop a system for generating road-representative turbulence in the NRC 9 m Wind Tunnel, named the Road Turbulence System (RTS). This endeavour was undertaken in support of a larger project to evaluate new and emerging drag reduction technologies for heavy-duty vehicles.
A multi-stage design process was used to develop the RTS for use with a 30% scale model of a heavy-duty vehicle in the NRC 9m Wind Tunnel. This paper documents this process, which included 1) an on-road measurement campaign to identify that target wind characteristics, 2) small-scale concept-development efforts to identify a passive approach to the problem, and 3) commissioning of the full-sized RTS in the NRC 9m Wind Tunnel. The wind-spectrum generated by the RTS is a good match to the target road measurements. Using a 30%-scale model of a heavy-duty vehicle, comparison of measurements in smooth and road-representative turbulent wind conditions were performed. The measurements show differences in the drag characteristics of the vehicle, and show differences in the drag-reductions associated with add-on devices such as side-skirts and boat-tails, highlighting the importance of representative turbulence for ground-vehicle aerodynamic evaluations.