Large-eddy simulation of a concave wall boundary layer

Large-eddy simulations (LESs) of a spatially evolving boundary layer on a concave surface are discussed. A second-order finite-difference method with a fully implicit time advancement scheme is used to integrate the incompressible Navier-Stokes equations. The dynamic subgrid-scale model is used to account for the effects of the unresolved turbulent motions. The simulations attempt to duplicate a set of laboratory experiments conducted at a momentum thickness Reynolds number of 1300. The simulation results generally compare well with the experimental data and accurately predict the structural changes that result from the destabilizing effect of concave curvature. Some discrepancies exist with the experimental data, and these appear to be related in part to the details of the turbulent inflow data used in the simulations. Slightly better agreement with the experimental data is obtained if inflow data with higher fluctuation levels and artificially enhanced streamwise coherence is used. The sensitivity to inflow conditions appears to be related to the amplification of existing structures within the curved section of the domain. The simulation using inflow data with enhanced streamwise coherence is shown to lead to the formation of distinct Taylor-Gortler vortices; whereas, the other simulations lead to a variety of weaker, less-developed secondary flow patterns. These results seem to suggest that the upstream flow history can exert a significant influence on the initial development of secondary flow structures in concave turbulent boundary layer flows.