A hybrid RANS/LES (Reynolds-averaged Navier-Stokes/large eddy simulation) approach based on one-equation S-A(Spalart-Allmaras) RANS model and one-equation Yoshizawa SGS(sub-grid scale) model was developed.The turbulent kinetic energy transport equation of the SGS model was transformed to an equivalent eddy viscosity transport equation

and then blended with the S-A model equation to generate a hybrid eddy viscosity transport equation

wherein both the SGS behavior and the grid-depending RANS-LES transition of DES were improved.The hybrid RANS/LES approach was then applied to simulate a supersonic

ramped cavity flow

where LES and DES were also implemented on the same mesh for comparison.It shows that the hybrid RANS/LES acts like LES in the free shear flow far away from the wall and outperforms LES and DES in the attached boundary layer.