Effect of the plenum-chamber diameter on the turbulent characteristics of a supersonic jet

The effect of the flow character in the plenum chamber of a nozzle on the high-frequency boundary of the spectrum of fluctuations at the boundary of a supersonic, strongly underexpanded jet of nitrogen exhausted from a circular sonic nozzle into the ambient space was experimentally studied. The Reynolds number in the plenum chamber of the nozzle with a given throat area was varied by changing the diameter of the subsonic region. The high-frequency boundary of the spectrum of turbulent fluctuations was evaluated on the basis of two-point correlation functions of time. The technique for measurement of these functions was based on molecular scattering of light. Radiation of two pulse lasers with a controlled delay between the pulses was used as a source of light. It follows from experimental results that the high-frequency boundary of the spectrum of turbulent fluctuations and the spectrum itself vary significantly depending on the Reynolds number of the flow in the plenum chamber.