Aerodynamics of a Pickup Truck: Combined CFD and Experimental Study 2009-01-1167

This paper describes a computational and experimental effort to document the detailed flow field around a pickup truck. The major objective was to benchmark several different computational approaches through a series of validation simulations performed at Clemson University (CU) and overseen by those performing the experiments at the GM R&D Center. Consequently, no experimental results were shared until after the simulations were completed. This flow represented an excellent test case for turbulence modeling capabilities developed at CU.

Computationally, three different turbulence models were employed. One steady simulation used the realizable k-ε model. The second approach was an unsteady RANS simulation, which included a turbulence closure model developed in-house. This simulation captured the unsteady shear layer rollup and breakdown over the front of the hood that was expected and seen in the experiments but unattainable with other off-the-shelf turbulence models. Details of the high performance computing effort required to produce these results are discussed. The third simulation employed a new closure model designed to include the effects of small-scale unsteadiness on the mean flow without actually performing time-accurate simulations. As expected, this reduces CPU time, disk storage, and data I/O times significantly. In this case, CPU time was reduced by 95%. An approach of this nature would greatly reduce design time and make CFD a more feasible option.