亜・遷音速流中におけるジェットの干渉による鈍頭物体底面部での圧力分布特性

Abstract

The objective of the present study is to experimentally make clear the mechanism of aerodynamic interaction, in particular pressure interaction, due to a jet located off-center at the base of a blunt body with angle of attack in subsonic to transonic flow. The correlation between change in pressure drag and local pressure distribution by issuing the jet toward the downstream is obtained in terms of four parameters: the jet deflection angle, the jet mass flow rate, the freestream Mach number, and the angle of attack of model. Results indicate that the interacted flow field is characterized by three components: jet entrainment, vortex, and turn of main flow round the corner of the model base. At lower angle of attack than 15 degrees, the interacted flow shows different mechanisms between the inner and the outer regions at the base. In the inner region, pressure increases due to a vortex produced by jet entrainment, in which the circulated flow yields a stagnation point at the base. This is a favorable effect in terms of thrust. However, larger deflection of jet decreases the pressure in this region due to breakdown of the vortex. On the other hand, in the outer region, pressure decreases due to disappearance of a vortex produced in the case of no jet. At higher angle of attack than 15 degrees, more main flow comes to turn to the base round its corner. Consequently, the base pressure tends to have a uniform distribution with increasing the angle of attack. Moreover, increase in the jet mass flow rate makes this trend prominent, where the pressure in the outer region decreases to a certain level. Meanwhile, this pressure interaction increases with the freestream Mach number, which is caused by two effects:turn of more main flow to the base due to compressibility and jet expansion due to decrease in the ambient pressure.