Improvement of the performance of a supersonic nozzle by riblets

This paper describes an experimental study of supersonic internal flow over a riblet surface mounted on a channel wall to reduce pressure loss and improve the performance of a supersonic nozzle. The magnitude of the static pressure in the pressure-rise region observed in channels with riblet surface became lower than that for a smooth surface, and the significance of its difference was indicated by uncertainty analysis estimated at 95 percent coverage. The Mach number distributions obtained by traversing a Pitot-tube showed that the separation point moved downstream and the size of the separation region became small when using riblets. Furthermore, it was found that the stagnation pressure loss reduction was as large as 56 percent in the uniform supersonic flow field at a Mach number of 2.0, and 29 percent in the separation region.