Performance of a Modified DDES for the Near Stall Flow Past a NACA0015 Airfoil

A modification of DDES with adaptive coefficient CDES (DDES-AC) is proposed to deal with the delay transition from RANS to LES in the stall flows over a NACA0015 airfoil. The coefficient CDES is adaptive with the flow patterns, quasi-2D shear layer or 3D full developed separation, which helps to reduce the eddy viscosity in the separated shear layer. The performance of DDES-AC is validated by computing the flows over a NACA005 airfoil with mild trailing edge separation and during dynamic stall. It is found that the “grey area” in the original DDES is exacerbated in the simulation of dynamic stall. The DDES-AC is effective in accelerating the transition from RANS to LES and alleviating the “grey area” to some extent.