Large eddy simulation of an equilibrium three-dimensional turbulent boundary layer

Large eddy simulation has been applied to prediction of an equilibrium three-dimensional turbulent boundary layer (TBL). Subgrid-scale stresses were parameterized using a Lagrangian dynamic mixed model. The predicted mean velocities and second-order statistics are in good agreement with direct numerical simulation results. Singlepoint statistics are also generally similar to those found in other equilibrium three-dimensional TBLs such as the flow over a rotating disk and the turbulent Ekman layer. The modification of shear stress producing structure by mean flow three-dimensionality was also investigated. Joint probability density functions show that in the buffer region the contribution to the shear stress from strong ejections is slightly larger than that from strong sweeps. The conditionally averaged velocity fluctuations in the buffer region indicate that streamwise vortices of the same sign as the near-wall mean streamwise vorticity produce strong sweeps but weakened ejections, whereas those with the opposite sign produce strong ejections but weakened sweeps. These features are found to persist within a moderate increase in the Reynolds number, corresponding to a 20% reduction in the peak mean crossflow velocity, and are consistent with similar measures obtained in the turbulent flow over a rotating disk.