The effect of underexpanded jet flow conditions on the supersonic core length

Abstract

Abstract The paper describes the results of measurements of the supersonic core length of underexpanded jets exhausted into a submerged space. Exhaustion of supersonic He, air, CO2, Ar, and SF6 jets into He, air, CO2, Ar, and SF6 at moderate Reynolds numbers for the laminar, transitional, and turbulent flow regimes is considered. These jets outflow from convergent nozzles with diameters of 0.52, 0.72 and 1.06 mm; the measurements are performed by a Pitot tube. The amplitude-frequency spectra of acoustic oscillations generated by the jets in the ambient space are measured. The experiments are performed in a low-pressure jet setup, which allows independently maintaining the Reynolds number of gas exhaustion from the nozzle and the jet pressure ratio. The jet setup is used to study exhaustion of a jet of one gas into the submerged space filled with another gas and the influence of the ratio of densities of these gases on the supersonic core length.