Numerical Investigation of Massively Separated Flows past RLG Using Advanced DES Approaches

Abstract

Unsteady and massively separated flows past the Rudimentary Landing Gear (RLG) are investigated using Delayed Detached-Eddy-Simulation (DDES) and Improved-DDES (IDDES) based on Shear Stress Transport model (SST). To eliminate the unfavorable influence of large numerical dissipation, a high order Symmetric Total Variation Diminishing (STVD) scheme with adaptive dissipation approach is implemented to better resolve the turbulence. Three sets of grid, including the coarse, mandatory and locally fine grids with 3.6, 11 and 13 million grid points, are applied to predict the massive separation and we find that grid density has a weak effect on the mean flows, but has a significant influence on the instantaneous flows. After investigating the flow features, both DDES and IDDES present acceptable agreements with the available experiments for the mean pressure, pressure fluctuations and surface flow patterns, and only small differences in some local regions occur. Due to the wall-modeled large-eddy-simulation (WMLES) mode, IDDES presents slightly more reasonable secondary separation and range of horseshoe vortex on the aft wheels than those by DDES. Furthermore, IDDES can present more reasonable root mean squares of pressure coefficients on the wheels, predict the shear layer instability a little more upstream and resolve smaller instantaneous structures than DDES.