Moving Ground Effects on the Wheelhouse Flows of Heavy Vehicles

Paper i proceeding, 2008

In the optimization of the aerodynamic design of road going vehicles the importance of ground simulation has been a well known fact for quite a long time. A correct simulation of the boundary conditions underneath the vehicle, including rotating wheels and moving ground, is of outmost importance in minimizing the drag coefficient. For heavy vehicles there are currently no moving ground facilities available for full scale testing due to their weight and size, however, some simple scale model experiments on the aerodynamic optimization of long haulage trucks with ground simulation have been reported recently. In the current study a detailed investigation of the flow structures in the front wheelhouse of a typical long haulage truck has been performed. Detailed tractor-trailer geometry, including wheelhouse and engine compartment, has been used, and focus has been put on the front wheel and wheelhouse. The flow structure in this region is extremely complex due partly to the wheel rotation and partly to the interference with the free stream flow as well as the cooling air flow. The objective of the study was to achieve an improved understanding of the wheel and wheelhouse flow in order to enable an optimized aerodynamic design and by that reduce the fuel consumption. Simulations using Computational Fluid Dynamics (CFD) were performed in order to predict the flow around the vehicle. Moving ground and rotating wheels was utilized to simulate real driving conditions. The flow entering and exiting the wheelhouse has been thoroughly investigated and the vortex structures originating from the wheel has been identified.