Optimal slip wall model for LES in the presence of pressure gradient effects*

The slip wall model for large-eddy simulation of turbulent flow is based on rigorous derivation from LES principles, in contrast to traditional equilibrium wall models which are based on RANS principles. It has been demonstrated that slip wall models outperform equilibrium wall models in prediction of turbulent separation, while maintaining superior grid convergence properties.

In practice, modeling the slip coefficient has proven difficult in coarsely resolved high Reynolds number flows; therefore, understanding the scaling behavior of an ideal slip length model is important to inform model development. Prior work observed in equilibrium boundary layers that the ideal slip length followed a consistent scaling behavior across a wide range of friction Reynolds numbers and grid resolutions. The approach is extended to study the behavior of an ideal slip wall model in the presence of pressure gradients and non-equilibrium effects. Additionally, a consistent slip boundary condition for the subgrid-scale stress is derived and is shown to improve skin-friction predictions in favorable pressure gradients. Applications to the Boeing speed bump and the NASA High Lift Common Research Model are presented.