Experimental investigation of supersonic gaseous injection into a supersonic freestream

Abstract

An experimental study of the mean and turbulent flowfield associated with low-angled supersonic gaseous injection into a supersonic freestream was performed. Air was injected at Mach 1.8, with an effective back pressure ratio of 3.0, through an orifice at an angle of 25 deg into a Mach 2.9 air freestream (Re/m - 15 x 10 6). Cross-film anemometry and conventional mean flow probe surveys were acquired across the plume at two downstream stations (xld = 20 and 40). Schlieren photography was used for qualitative flow visualization. Turbulence measurements included contours of the turbulent kinetic energy and the full compressible Reynolds shear stresses in both the x-y and x-z planes. Mean flow data included Mach number, three-dimensional velocity components, and vorticity. The measurements indicated that the mean and turbulent flow structure of the injection plume were strongly influenced by the presence of a counter-rotating vortex pair (\ux |max « 15,000 /s). The turbulent kinetic energy was found to have two peaks colocated with the vortices. The turbulent shear stress distributions across the plume were found to be highly three dimensional and complicated by both the additional strain rates associated with the vorticity and turbulent convection. The present results also implied that the compressibility terms in the Reynolds shear stress accounted for about 67.0-75.0% of the total shear stress level, i.e., up'v'lpu'v' and up'w'/pu'w' were in the range of 2.0-3.0.