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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.

Experiments are carried out on a blunt-cone-cylinder-flare geometry to study the effect of Mach 2.65 jet plume interaction with Mach 5 freestream on overall aerodynamic coefficients. Supersonic jet plume pressure ratios P j ∕P inf of 0 to 158 are simulated, and the angle of attack α is varied from 4 to −4 deg. Flow features are captured through Schlieren and oil flow visualization. The isolation of load measuring and load nonmeasuring parts and elimination of jet reaction force are confirmed through tests. Under jet-off conditions, with an increase in the angle of attack, the flow separation on the leeward side moves toward the nose, whereas, on the windward side, the separation moves toward the base. Similar behavior is seen under jet-on conditions. However, due to jet-plume-freestream interaction, separation is more pronounced on the leeward side. In general, as P j ∕P inf increases, the aerodynamic coefficients decrease irrespective of angles of attack. At the maximum P j ∕P inf of 158, C N , C m , and C A are decreased by 15, 22, and 30%, respectively. Also X CP moves toward the nose by 1.15D, 0.6D, and 0.25D for α 1, 2, and 4 deg, respectively.= pitching moment about nose NF = normal force, N P = static pressure, bar P inf = freestream static pressure, bar P j = jet static pressure, bar P j ∕P inf = jet pressure ratio P 0j = jet nozzle pressure, bar P 0 = total pressure, bar P 01 = tunnel stagnation pressure, bar P 02 = total pressure behind normal shock, bar Re = Reynolds number SF = side force, N S ref = reference area, mm 2 T = static temperature, K T 0 = total temperature, K T 01 = tunnel stagnation temperature, K V ∞ = freestream velocity, m∕s X = coordinate system X CP = center of pressure Y = coordinate system Z = coordinate system α = angle of attack γ = Specific heat ratio ρ ∞ = freestream density, kg∕m 3 ∞ = freestream

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