Experimental investigation of low blow ratio blended missile body supersonic jet interaction flowfields

An experimental investigation of the flowfields created by injecting normal to a blended missile fuselage at low blowing ratios into a Mach 3.0 (Re/m = 5.5xl0) freestream was performed. These experiments were performed to document the flow dynamics at low blowing ratios with the goal of understanding observed force reversal created by the jet interaction. The injector flow conditions tested were: Injection Mach number 1-3, pressure ratio 120, temperature ratio 0.7-2.33, the ratio of specific heats 1.4-1.67, and jet momentum ratio parameter 0.003-0.1. The experimental methods include particle image velocimetry (PIV), surface oil flow visualization, 5-hole pitot/cone-static pressure probe, and pressure sensitive paint (PSP). The measurements include surface oil flow visualizations, mean Mach number contours, mean pressure contours, mapping of two dimensional planar velocity vectors, and surface pressure distribution. The data summarized in this paper provide a complete characterization of the mean flow properties, as well as the jet plume surface interaction topologies. Introduction Jet interaction flowfields have a myriad of applications in the aerodynamics and fluid mechanics regime. One major application, currently being implemented by the United States Army, is the highspeed intercept missile. Rapid and accurate maneuvering capability, and short response time are very important requirements of the intercept missiles. Aerodynamic surfaces, used to provide the missile lateral control, have limited control at higher altitudes and speeds, but the lateral control jets provide better maneuverability and better response time over a wide range of altitudes and speeds. However, the effectiveness of the lateral control jet is highly dependent on the aerodynamic interactions of the jet and the crossflow. Jet interaction flowfields are also highly applicable for the scramjet combustor " Graduate Research Assistant, Member AIAA Associate Professor, Senior Member AIAA applications for the high-Mach vehicle systems. In addition, boundary layer control (i.e., drag reduction) and stall suppression are some of the other applications of this flowfield. Because of the numerous applications, injection of gaseous jets into supersonic freestream has been studied for many decades now" and the flowfield is well characterized. In 1960s most investigations were done to characterize the flowfield structure using surface oil flow visualization, schlieren photographs, mean flow measurements, concentration measurements, and mass flow rates. Later the attention was concentrated on different parametric studies for the supersonic reaction control jets, e.g.; Mach number, injectant specific heats, jet to free steam pressure ratio, jet momentum parameter ratio, jet to free stream temperature ratio, injection angles, the surface curvature, injector shapes, etc. Turbulence modeling was very limited due to scarcity of the accurate and advanced experimental database. Schetz' ""* documented that for a fixed Mj and fixed jet geometry the displacement of the Mach disk varies as P/, and the penetration height is proportional to the half power of the jet mass flow rate. Higher jet Mach number increases the penetration height, but this phenomenon is not quite significant beyond Mach numbers 2.0. Billig ' later developed the model further for a different jet angles and turbulent mixing after the Mach disk, using the modified effective backpressure concept. Santiago mapped the instantaneous velocity distribution of sonic transverse jet into a Mach 1.6 free stream. A two-component frequency pre-shifted LDV system with over 2200 measurement locations in the transverse midline plane was employed to provide better resolution and accuracy of the overall structure of the mean and turbulent flowfield. A number of studies" focused on the turbulence mixing and vorticity generation in the crossflow. The wake vortices originate in the crossflow boundary layer immediately downstream of the jet. Large-scale counter rotating vortices in the wake engulfs the crossflow fluid from below up into the jet and transports jet fluid down into the wake, thus ensuring better mixing of the fluids. The effects of compressibility on the free shear layers were also considered to be an important research interest in many of previous research