EXPERIMENTAL INVESTIGATION OF SUPERSONIC GASEOUS INJECTION INTO A SUPERSONIC FREESTREAM

An experimental study of the mean and turbulent flowfield associated w ith low-angled supersonic gaseous injection into a supersonic freestre am 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 a nd conventional mean flow probe surveys were acquired across the plume at two downstream stations (x/d = 20 and 40), Schlieren photography w as used for qualitative how visualization. Turbulence measurements inc luded contours of the turbulent kinetic energy and the full compressib le Reynolds shear stresses in both the x-y and x-z planes. Mean flow d ata included Mach number, three-dimensional velocity components, and v orticity. The measurements indicated that the mean and turbulent flow structure of the injection plume were strongly influenced by the prese nce of a counter-rotating vortex pair (\w(x)\(max) approximate to 15,0 00/s). The turbulent kinetic energy was found to have two peaks coloca ted with the vortices. The turbulent shear stress distributions across the plume were found to be highly three dimensional and complicated b y both the additional strain rates associated with the vorticity and t urbulent convection. The present results also implied that the compres sibility terms in the Reynolds shear stress accounted for about 67.0-7 5.0% of the total shear stress level, i.e., <(u rho'nu')over bar>/<(rh o u'nu')over bar> and <(u rho'w')over bar>/<(rho u'w')over bar> were i n the range of 2.0-3.0.