A numerical methodology to predict exhaust plumes of propulsion nozzles

A simple methodology to simulate the mixing layers that occur between nozzle exhaust jet and the external air is proposed. The method is based on a simplified model of the plume, that replaces the mixing layer with a contact discontinuity surface, thus avoiding the cumbersome calculation of the turbulent mixing of two flows with different chemical composition. The contact discontinuity is numerically treated by an advanced fitting technique, capable of tracking the discontinuity by points floating over the computational grid. The numerical method is discussed and its capability is demonstrated with validation tests, as well as with a discussion of some practical applications for underexpanded nozzle flows.