Jet Interaction Effects on the Base Pressure of a Blunt Body in Hypersonic Flow

Abstract

An experimental study was conducted by using the Nagoya University Shock Tunnel to examine aerodynamic interaction of a jet with the base pressure of a blunt body model in a hypersonic flow. Here in this study, we are concerned with the jet interaction at a high angle of attack, which has not been well known so far. Pressure was measured at ten pressure taps which were distributed at the base in a two coaxial rings-shaped manner;hereafter referred to as the inner and outer rings, where the jet was located between them. In this study, two parameters are employed with regard to the jet: the deflection angle and the mass flow rate. At a high angle of attack of 40 degrees, the pressure distribution shows asimilar pattern to the case of side-jet blowing to a freestream. That is, along the outer ring, the pressure is increased due to a bow shock in front of the jet, while at the inner ring, the pressure is locally decreased because of a vortex produced by the jet entrainment. This trend becomes prominent with the mass flow ratio, which is favorable for augmenting the jet thrust. By deflecting the jet toward outside, the jet becomes close to the outer ring, so that the pressure is decreased there. This is considered to be due to an entrainment effect. Integrating these pressure changes by jet interaction leads to appreciable quantity of interaction force. Under the present conditions, the maximum value of integrated base drag becomes as large as about 7.5% of the axial force of the blunt body at an angle of attack of 30 degrees.