An in-depth numerical investigation of a supersonic cavity-ramp flow with DDES method

Abstract

Delayed detached eddy simulation (DDES) studies of the highly unsteady supersonic cavity-ramp flow have been successfully carried out. It is generally believed that accurate prediction of the compressible unstable shear layer coupled with the followed reattaching process is a big challenge for DDES method. In the current DDES studies based on an engineering affordable mesh, significant improvements are achieved assessed by the agreements with experimental data. Effects of various crucial parameters related to DDES have been analyzed in detail. First of all, it is found that a fine mesh with sufficient computation domain is required to obtain accurate results, and the time step needs to be properly set. Secondly, effect of the definition of subgrid length scale Δ is observed, especially in the initial region of shear layer. The original Δ form of DDES method tends to depress the development of instabilities in the shear layer. Analysis on the physical causes is presented. Moreover, unexpected performance of DDES' shield function fd for the current case is observed and analyzed, whose influence on the simulated characteristic in the downstream region has also been discussed in particular.