In the present paper, we give a brief overview of the studies of supersonic jet flows which were performed recently with the aim of gaining experimental data on the formation of the shock-wave structure and jet mixing layer in such flows. Considerable attention is paid to a detailed description of discharge conditions for supersonic jets, to enable the use of measured data for making a comparison with numerical calculations. Data on the 3D flow structure in the mixing layer of the initial length of a supersonic jet are reported. Scientific interest in this phenomenon is due to its practical significance in studying the possibility of intensifying the mixing process as well as in studying the sound-generation process.

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Shock-Wave Structure of Supersonic Jet Flows

The steady-state structure of supersonic underexpanded jet flow at Ma = 1 is experimentally investigated. The measured total pressure distributions are presented in different cross sections and along the jet axis. Certain distinctive features of the supersonic jet flow are revealed. Among these are considerable fluctuations of the density distribution in the mixing layer formed behind the triple point on the normal shock in the jet. They are due to the presence of vortex structures in the internal mixing layer. The data obtained are used in testing the results of numerical calculations.

Gasdynamic structure of an axisymmetric supersonic underexpanded jet

The results of experimental researches of intensity fluctuations of a laser beam propagating through a supersonic flooded jet are presented. The laser beam propagates across the jet at various distances from a Vitoshinskii nozzle. The experiment was carried out in an Eiffel chamber at pressure ratios from 1.7 to 7 at two modes of the outflow of the jet: with the use of chevrons on the outlet nozzle and without chevrons. Dependencies of the dispersion and fluctuation spectra on pressure and distances from the nozzle are determined. The inner scale of turbulence is estimated.

Intensity fluctuations of a laser beam propagating through a supersonic flooded jet

The flow structure behind the Mach disk in the first cell of free supersonic underexpanded jets exhuasting from nozzles of different geometric Mach numbers at nozzle exit was examined. Flow visualization pictures obtained with the help of the direct-shadow method, the schlieren method, and the laser sheet technique are presented. It is shown that, in the subsonic zone behind the Mach disk of free supersonic non-isobaric jets exhausting from conical nozzles with Ma = 2.5 and Ma = 3 in a wide range of gas-dynamic regimes, the shape of the Mach disk corresponds to that of a normal shock, and this shape undergoes no deformation, i.e. no recirculation region is registered behind the Mach disk. Experiments using the contactless panoramic laser PIV method were performed. From measured fields of flow velocity at outflow regimes of free supersonic jet with Npr = 8.5 and Ma = 1.5, the non-occurrence of flow recirculation zone behind the Mach disk was demonstrated.

Flow structure behind the Mach disk in supersonic non-isobaric jet

A method of calculating the pressure from the velocity field measurement data by using the PIV contactless technique is considered in the work. The pressure distribution was calculated by using the...

V. M. Boyko

Papers

Investigation of supersonic nonisobaric jet structure