A model to predict the Mach reflection of the separation shock in rocket nozzles

In case of high overexpansion, the exhaust jet of the supersonic nozzle of rocket engines separates from nozzle wall because of the large adverse pressure gradient. At the same time, to match the pressure of the separated flow region, an oblique shock is generated which evolves through the supersonic jet starting approximately from the separation point. This shock reflects oil the nozzle axis with a Mach reflection. Thus a peculiar Mach reflection takes place whose features depend on the upstream flow conditions, which are usually not uniform. A simplified model is presented which is a first step to predict the expected features of Mach reflection depending oil the nozzle shape and oil the position of the separation point along the divergent section of the nozzle.