Steady RANS modelling has been carried out for a symmetrical double-sharp-fin configuration with an inclination angle 15°, Mach 3.92 and Reynolds number Re_δ = 3.08 x 10⁵. Grid refinement and turbulence model influences using ω-based Reynolds Stress model (RSM), one-equation Eddy Viscosity Transport and two-equation Shear Stress Transport, have been studied and predicted wall pressure distributions were in good agreement with experiment data. RSM model surface flow topology was found to be in better qualitatively agreement with experimental oil-flow visualization than those from other two models. The secondary separation phenomenon observed in the experiment was successfully reproduced by the RSM model, due to its ability to evaluate correct level of turbulence kinetic energy that is critical in determining pseudo-laminar state of an embedded reversed flow underneath the main cross-flow vortex. Three-dimensional flow structures demonstrated that the initially weak secondary separation has been further strengthened in span-wise direction towards the central separated zone.