Annotation. The visualization of gas flows expanding from supersonic nozzles into flooded space under the cluster formation conditions is considered. The technique of exciting the supersonic flow by a well-focused high-voltage electron beam is applied in conjunction with the scanning equipment for the gas objects. The reasons for the secondary cluster jet formation in a flow of easily condensing gases are discussed. A comparison is made between the formation of a traditional spindle-shaped jet and a secondary cluster one. The measurement results of the diameters of the traditional and cluster jets in maximum sections, obtained by the photometry method, are presented. It is shown that for the characteristic sizes of cluster jets of condensing gases, the dependence on parameters proposed by Sherman and Ashkenas is applicable in the entire range of the studied stagnation and background pressures. The similarity of the formation processes of traditional monomeric jets and secondary cluster jets under the conditions of developed condensation of the initial supersonic flow is supposed.

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Abstract. We present the results of direct numerical simulation of stably stratified open channel flow. The simulation was conducted in a frame of reference moving with the mean flow. The chosen setup allowed us to apply temporal filtering without affecting the long-living large-scale laminar and turbulent patches to see the dynamics of the processes on their boundaries. The main goal of the paper was to investigate the vorticity balance in different parts of the flow. It was shown that boundaries between laminar and turbulent patches contain weak large-scale vortex structures sustained by the baroclinic generation.

The spectral study results of a supersonic clustered argon flow stimulated emission in the region of particle excitation (on an electron beam) and downstream are presented. Anomalies in the luminescence of the traditional spindle-shaped jet and the flow of heavy clusters (“wake”) are discussed. Possible causes of the observed anomalous phenomena are presented on the basis of the given comparisons of the results obtained.

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