Feasible suggestions of scale-adaptive simulation approach based on the high-fidelity large-eddy simulation of supersonic turbulent boundary layer

Abstract

Large-eddy simulation (LES) of the Navier–Stokes equations is carried out to investigate the supersonic turbulent boundary layer (STBL) developing over a flat plate at free-stream Mach number M∞=2.0 and Reynolds number Reδ≈ 13 500. The seventh-order weighted essentially non-oscillatory (WENO-7) scheme is adopted to ensure calculation accuracy. To demonstrate the credibility of the proposed improvements, a posteriori test is conducted. Other LES-like methods are also adopted for comparison. The validation results show that WENO-LES can provide credible predictions when grid resolution is sufficient. Thus, current LES results can be regarded as a reliable database for further analysis. The distributions of flow topologies and turbulent statistics are obtained after time average operation. A preliminary conclusion can be drawn that the position y+≈ 14 in buffer layer may be the appropriate interface for Reynolds-averaged Navier–Stokes (RANS) and LES computations of LES-like methods in STBL. Diverse length scales in LES-like methods are calculated based on high-fidelity flow fields. On this basis, a blending function is added to the original von Karman length formula. A dissipation-adaptive length scale is proposed for the scale-adaptive simulation (SAS) method. A comparison of the original SAS and delayed-DES (DDES) methods reveals that the improved method exhibits grid-independent characteristics of RANS/LES interface. Furthermore, the coherent vortical structures and flow visualization of the a posteriori test indicate that the improved method has a satisfactory ability to promote the generation of small-scale structures and to capture turbulent fluctuations.