Wheel and underbody aerodynamics have become important topics in the search to reduce the aerodynamic drag of the heavy trucks. This study aims to investigate, experimentally as well as numerically, the local flow field around the wheels and in the wheel housing on a heavy truck; and how different approaches to modelling the wheel rotation in CFD influences the results. Emphasis is on effects due to ground simulation, and both moving ground and wheel rotation were requirements for this study.
A 1:4-scale model of part of a heavy truck geometry has been developed. During the model design numerical simulations were used to optimise the shape, in order to replicate the flow field near the wheel of a complete truck. This was done by changing the flow angles of the incoming and exiting flows, and by keeping the mass flow rates in to, and out of, the wheel housing at the same ratios as in a reference full size vehicle. To reduce blockage effects, the model was sectioned to reduce both height and width. In the experiments, pressure sensors and static pressure taps located in the wheel housing were utilised, and the simulations replicated the boundary conditions of the wind tunnel experiments, both in terms of the geometry of the model and wind tunnel as well as the modelling of the ground simulation.
It was found that the wheel wake structures changed significantly when ground simulation was utilised. The main outflow through the wheel housing was influenced by the wheel rotation and took place further upstream, which resulted in large differences in the flow field downstream of the wheel. The influence of different strategies for modelling the wheel rotation in CFD was investigated and it was found that the Sliding Mesh approach was the most accurate method.
