LARGE-EDDY SIMULATION OF AN EQUILIBRIUM 3-DIMENSIONAL TURBULENT BOUNDARY-LAYER

Large eddy simulation has been applied to prediction of an equilibrium three-dimensional turbulent boundary layer (TBL). Subgrid-scale stres ses were parameterized using a Lagrangian dynamic mixed model. The pre dicted mean velocities and second-order statistics are in good agreeme nt with direct numerical simulation results. Single-point statistics a re also generally similar to those found in other equilibrium three di mensional TBLs such as the flow over a rotating disk and the turbulent Ekman layer. The modification of shear stress producing structure by mean how 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 fr om strong sweeps. The conditionally averaged velocity fluctuations in the buffer region indicate that streamwise vortices of the same sign a s the near-wall mean streamwise vorticity produce strong sweeps but we akened ejections, whereas those with the opposite sign produce strong ejections but weakened sweeps. These features are found to persist wit hin a moderate increase in the Reynolds number, corresponding to a 20% reduction in the peak mean crossflow velocity, and are consistent wit h similar measures obtained in the turbulent flow over a rotating disk .