Transonic resonance tones in orifice and pipe jets

This paper investigates the flow resonance while the jet is issued out from a nozzle at transonic Mach numbers. In present study the jets emerging out from orifice and pipe nozzles are considered. The jet flow diameter of orifice and pipes is 10 mm, and the length of the pipe is varied in the range of 1 ≠L/D ≠6. The pressure ratio of the jet flow is varied in the range of subsonic to supersonic Mach numbers; however the study predominantly concentrates on transonic regimes. Results indicate that distinct transonic resonance tones occur in the range of transonic Mach numbers (0.95 to 1.01). Unlike screech that occurs during the presence of shock cells, the transonic frequencies slightly increase with Mach number. Moreover numerous multiple non-harmonic frequency tones are observed during this transonic resonance thus indicating the non-linearity in the flow resonance. In case of pipe nozzles, the transonic tones tend to diminish with increase in pipe length and cease to exist beyond a certain length.