Validation of Large Eddy Simulation in a relaminarizing boundary layer flow

Coexistence of laminar, transitional and turbulent flow regimes is very common in blood flows through arteries, airflows in human respiratory systems, and indoor airflow etc. Due to the complexity of flow physics involved, most Reynolds-averaged Navier-Stokes (RANS) turbulence models are not suitable for these flows because they are designed primarily for high Reynolds number turbulent flows. In this paper, large eddy simulation with dynamic subgrid scale model has been applied to simulate the flow in a relaminarizing boundary layer that undergoes reverse transition from turbulent state to laminar one. Simulated mean velocities and turbulent intensities are in good agreement with corresponding experimental data at different streamwise positions where different flow regimes exist. The appropriateness of dynamic subgrid scale model for the study of relaminarizing boundary layer flow is demonstrated by the variation of subgrid constant: it is somewhat constant in fully turbulent regime, decreases in transitional regime and reaches zero in laminar regime. Comparison of the experimental data and computational results from three low Reynolds number RANS models shows that they do not adequately predict the flow relaminarization. The present study suggests the use of large eddy simulation with dynamic model in the study of complex flows where a combination of flow regimes (laminar, transitional, and turbulent) may exist.