Transonic wing stall of a blended flying wing common research model based on DDES method

Numerical simulation of wing stall of a blended flying wing configuration at transonic speed was conducted using both delayed detached eddy simulation (DDES) and unsteady Reynolds-averaged Navier-Stokes (URANS) equations methods based on the shear stress transport (SST) turbulence model for a free-stream Mach number 0.9 and a Reynolds number 9.6 ? 106. A joint time step/grid density study is performed based on power spectrum density (PSD) analysis of the frequency content of forces or moments, and medium mesh and the normalized time scale 0.010 were suggested for this simulation. The simulation results show that the DDES methods per-form more precisely than the URANS method and the aerodynamic coefficient results from DDES method compare very well with the experiment data. The angle of attack of nonlinear vortex lift and abrupt wing stall of DDES results compare well with the experimental data. The flow structure of the DDES computation shows that the wing stall is caused mainly by the leeward vortex breakdown which occurred at x/xcr=0.6 at angle of attack of 14?. The DDES methods show advantage in the simulation problem with separation flow. The computed result shows that a shock/vortex interac-tion is responsible for the wing stall caused by the vortex breakdown. The balance of the vortex strength and axial flow, and the shock strength, is examined to provide an explanation of the sen-sitivity of the breakdown location. Wing body thickness has a great influence on shock and shock/vortex interactions, which can make a significant difference to the vortex breakdown behavior and stall characteristic of the blended flying wing configuration.