Experimental investigation of the nozzle roughness effect on streamwise vortices in a supersonic jet

The roughness of the internal nozzle surface plays a substantial role in the formation and development of streamwise vortex structures in the initial region of supersonic jet. The intensity, transverse size, and extent of the vortex structures, in turn, depend on the geometric shape and size of the microroughness and on their position in the nozzle. The measurements in the shear layer in the immediate vicinity of the nozzle indicate a laminar flow character in the nozzle boundary layer at Reynolds number Red approximately 106, which is consistent with experimental data on the laminar-turbulent transition in wind tunnels.