Wall modeled large eddy simulation of a spatially developing non-equilibrium turbulent boundary layer

Present study aims to examine the performance of wall models in a three-dimensional turbulent boundary layer (3DTBL). A wall modeled LES is conducted for a square-duct flow where a spatially-developing 3DTBL is generated by a 30-degree bend, following the experiment of Schwarz & Bradshaw (JFM, 1994). The cross-stream pressure gradient imposed by the bend creates a skewed velocity profile, where the surface streamlines are deflected by up to 22 degrees relative to the centerline velocity. The Reynolds number based on the momentum thickness and the free-stream velocity ranges from 4000 to 9000. An equilibrium wall model is used with a coarse mesh deploying 10 to 20 cells within the local boundary layer thickness. Prediction of mean velocities, wall pressure, and turbulence quantities from the wall modeled LES are in reasonable agreement with the experiment. Effectiveness of the equilibrium wall model in capturing non-equilibrium effects (e.g., evolution of Reynolds-stress budget in the outer layer) will be discussed.