Large Eddy Simulation of supersonic jet plumes from rectangular con-di nozzles

A Large Eddy Simulation investigation is described of a supersonic jet discharging from a rectangular convergent–divergent nozzle at a Nozzle Pressure Ratio typical of military aircraft propulsion. Accurate inlet conditions and an appropriate choice of sub-grid scale modelling, as well as appropriate mesh design, are essential for good LES predictions. The present work adopts an LES inlet condition generation method based on a rescaling/recycling method (R2M) and the Piomelli and Guerts SGS (PGSGS) model, which has the attractive feature of being independent of filter width (mesh size), but has not previously been used in combined boundary layer/free shear flow. Results show that the R2M technique was able to generate an unsteady, correlated 3D velocity field at the nozzle inlet plane which matched available experimental data and possessed physically consistent spatial and temporal correlations. Using an appropriately refined mesh, turbulence was sustained through the nozzle after experiencing strong favourable pressure gradient induced relaminarisation effects, enabling good prediction of the nozzle exit boundary layer state and hence the near field jet plume development. The PGSGS model was observed to improve predictions compared to the standard Smagorinsky SGS model.