Effect of trailing ramp angles in strut-based injection in supersonic flow

Experimental and numerical studies are conducted on supersonic mixing of air injected from struts of various trailing ramp angles with freestream air at Mach number 1.63. By providing an alternate trailing ramp on the strut, streamwise vortices in spanwise row configuration are generated. In the present study, various alternate trailing ramp struts were examined and their capability to enhance supersonic mixing was evaluated. Numerical simulation of the flow field with struts of various trailing ramp angles such as 2.86, 5.71, 8.53, 11.31, 14.04, 18.43, and 26.57 deg is also carried out. From the numerical results, it is seen that mixing enhancement is better only for the strut with a 14.04 deg ramp angle compared with a plain strut. Three types of struts are considered for the current experimental investigation: plain strut, two relieved ramp struts 2RRS-14.04 deg, and three relieved ramp struts 3RRS-14.04 deg. Diagnostic methods employed are Mie scattering combined with image processing, time-averaged schlieren and timeresolved high-speed shadowgraph images, velocity measurement using laser Doppler velocimetry, and total pressure loss measurements. Numerical simulation of the flowfield is performed using the commercially available software Fluent.