Affiliations: Aerodynamics Division, Defence Research and
Development Laboratory, Hyderabad, India | Department of Aerospace Engineering, Indian Institute
of Technology, Kanpur, India. E-mail: erath@iitk.ac.in
Abstract: Numerical simulation of scramjet asymmetric nozzle flow is carried
out to visualize and investigate the effects of interaction between engine
exhaust and hypersonic external flow. The Single Expansion Ramp Nozzle (SERN)
configuration studied here consists of flat ramp and a cowl with different
combinations of ramp angle and cowl geometry. Using PARAS 3D, simulations are
performed for a free stream Mach number of 6.5 that constitutes the external
flow around the vehicle. Appropriate specific heats ratio has been simulated
for the jet and free stream flow. External shock wave due to jet plume
interaction with free stream flow, the internal barrel shock wave and the shear
layer emanating from the cowl trailing edge and sidewalls are well captured.
Wall static pressure distribution on the nozzle ramp for different nozzle
expansion angles has been computed for both with and without side fence. Axial
thrust and normal force have been evaluated by integrating the wall static
pressure. Effect of cowl length variation and side fence on the SERN
performance has also been studied and found to be quite significant. Based on
this study, an optimum ramp angle at which the SERN generates maximum axial
thrust is obtained. SERN angle of 20o was found to be optimum when the flight
axis coincides with nozzle axis.