Base flow and exhaust plume interaction. Part 1: Experimental study

An experimental study of the flow field along an axi-symmetric body with a single operating exhaust nozzle has been performed in the scope of an investigation on base flow-jet plume interactions. The structure of under-expanded jets in a co-flowing supersonic free stream was described using analytical and physical models. Results of a single nozzle plume with a high supersonic exit Mach number of 4 exhausting in co-flowing supersonic free streams of Mach 1.96 and 2.98 are presented for a number of jet stagnation pressure to free stream static pressure ratios, ranging from Ptj/ Poo = 350 to no-jet flow at Mach 1.96 and from Ptj/ Poo = 600 to no-jet flow at Mach 2.98. The data consists of detailed five-hole probe Pitot pressure and flow direction surveys behind the model across the plume and of dynamic surface pressure measurements at the base of the model using three separate pressure taps. The five-hole probe Pitot pressure surveys clearly show the physical nature of the flow, e.g., the location of the various shock waves, expansion fans, and shear layers. The dynamic base pressure signals showed a resonance frequency of the pressure transducers. After filtering out the resonance frequency no distinct frequency was present in the dynamic base pressure signais. Apart from signal noise the base pressures showed a steady behaviour.Aerospace Engineerin