Experimental Investigation of the Nozzle Roughness Effect on the Flow Parameters in the Mixing Layer of an Axisymmetric Subsonic High-Velocity Jet

The paper presents the results of an experimental investigation of the mixing layer parameters in the initial regions of transonic jets issuing from convergent nozzles with different internal roughness at the same Mach number in the jet core. It is shown that the mixing layer characteristics, namely, the radial profiles of the measured total pressure and the r.m.s. total pressure fluctuations, are self-similar in nature at distances greater than 1.5 of the nozzle exit diameter from the exit. The possibility of applicating nozzles with an increased degree of the internal surface roughness in investigating high-velocity jet flows is shown.