This study reports the Computational Fluid Dynamics (CFD) results of a swirling flow induced by introducing a helical insert inside a supersonic nozzle. The CFD simulation shows a very complex unsteady, non-axisymmetric flow pattern for the swirl flow inside the nozzle.The flow is investigated by solving the Reynolds averaged Navier Stokes (RANS) equations with k- and Reynolds Stress Model (RSM) turbulence models to predict the flow patterns and the type of swirling flow. Computations are conducted for a range of nozzle pressure ratios with and without swirl inside the converging–diverging nozzle. The study has revealed a new understanding and data for flow features such as shock location, mass flow rate and anisotropic turbulence.