Investigation of the rear support interference on the aerodynamic characteristics of the RRJ-95 model in the T-128 transonic wind tunnel

The interference of the rear sting and the crescent-shaped rigid strut on the aerodynamic characteristics (drag, lift, pitching moment and base pressure coefficients) of the Russian regional jet model RRJ-95 is investigated in the TsAGI T-128 transonic wind tunnel at Mach numbers ranging from 0.7 to 0.88. The rear sting interference is studied experimentally. The weak interference (far field from the cone parts of the sting and the crescent-shaped strut) is evaluated within the framework of the small-disturbance theory with due regard for compressibility according to Prandtl-Glauert. The effect of the rear sting position variations relative to the model due to the sting deformation under the action of lift and pitching moment on the aerodynamic characteristics of the model is shown. The position of the point of applying the lift increment caused by the dummy rear sting interference is determined depending on the Mach number, angle of attack, model configuration, mutual position of the dummy sting and the fuselage. For better understanding of the flow physics, the flow visualization is performed by the color oil method in the area of the fuselage afterbody-fin sting-dummy rear sting joint. The analysis reveals a rather complicated flow nature in the base region. The presence of the wing changes the rear sting interference as compared with the fuselage alone.