Effect of Nozzle Divergence Angle on Plume Expansion In\ud Outer-Space Conditions

We carry out numerical simulations to investigate\ud the effect of nozzle divergence angle on back flow of\ud plume expansion into rarefied atmosphere.\ud Results are\ud obtained using open source compressible computational\ud fluid dynamics (CFD) solver.\ud Non-equilibrium slip and\ud jump boundary conditions for velocity and temperature are\ud implemented to capture rarefaction rarefaction effects in\ud the slip flow regime. The solver has been validated with\ud the experimental data for a nozzle flow in the slip flow\ud regime. We explore the non-linear non-equilibrium gas flow\ud physics of a supersonic jet expansion. We report results of\ud pressure, heat and drag coefficients for different divergent\ud angles (\ud 12\ud 0\ud ,\ud 15\ud 0\ud and\ud 20\ud 0\ud ) at 80 km altitude conditions. The\ud slip based results for heat loads significantly under-predict\ud the no-slip ones, while for pressure and drag coefficients,\ud deviations are found to be minute. It is noticed that thrust\ud coefficient of nozzle increases with increase in divergence\ud angle, however, nozzle with divergent angle of\ud 15\ud 0\ud led to\ud minimum drag and heat transfer load on the critical region.\ud The current study is important from the perspective of the\ud overall aero-thermodynamic design of a typical supersonic rocket model operating under rarefied conditions