Typical model design to measure aerodynamic coefficients in the presence of supersonic plume

Abstract

A typical model design was carried out to study the effect of plume–freestream interaction on aerodynamic coefficients. Towards this, a blunt-cone-cylinder-flare model was designed and fabricated. A strain gauge balance was accommodated to measure forces and moments due to plume–freestream interaction. The criticality of the model design such as isolation of metric–non-metric parts and elimination of jet reaction force were addressed in this paper. A finite element analysis was carried out to ensure proper isolation of metric and non-metric parts. The results showed that the maximum deflection of the model under aerodynamic loads is 0.41 mm, whereas the clearance between the metric and non-metric parts is 1.35 mm. Also, the experiments under plume alone condition revealed that the aerodynamic coefficients (CN, Cm and CA) have negligible values of the order of 0.003, 0.008 and 0.009, respectively, which ascertain the isolation of metric–non-metric parts and jet reaction force. The numerical and experimental results showed that the model design is in order. Also, typical experiments were carried out at α = 4° to study the plume–freestream interaction and the results show that as the jet pressure ratio (Pj/Pinf) increases, loss in CN, Cm and CA is observed.