Evaluation of Advanced Turbulence Models for High-Reynolds Number External Flow

In this report several modern turbulence modeling techniques with applications to high-Reynolds number external flow are critically evaluated. Fully developed turbulent channel flow and the flow past the Ahmed body with a slant angle of 25◦ are both used to benchmark several LES and DES models for turbulence closure. Channel flow is simulated at two different Reynolds numbers and both the LES and DES approaches are found to exhibit predictive capabilities but with several limitations, especially at the higher Reynolds number. The flow past the Ahmed body is validated against several experimental measurements. The improved delayed detached eddy-simulation (IDDES) model is found to yield the best overall drag prediction, but the wall-modeled LES approach is more robust across a wide range of grid resolutions. The computational effort required to perform the Ahmed-body simulations is summarized together with recommendations for the future use of the turbulence modeling techniques that are evaluated herein.