CFD investigation of mesh, boundary condition and location, and the effect of turbulence models on the turbulent separated flow over a forward-backward-facing step. A numerical model was set up to replicate and compare with the model in the literature. The Reynolds number, Re, is 1.7E5  based on step height 50 mm and obstacle length L = 10H. The freestream velocity of air at the inlet is 50 m/s. The simulation was performed using the ANSYS software.