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