Issue: 1 , Volume: 1770 , Уear of publication: 2016

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.