Flow Separation Phenomena in Subscale Rocket Nozzles

Separated flows in rocket nozzles due to overexpansion are known to lead to side loads on the nozzle. To investigate the origin of side loads in overexpanded rocket nozzles, experiments have been conducted with wall pressure measurements, Schlieren pictures and infrared imaging. Also numerical simulations were made. Especially the origin of a side load peak at a low pressure ratio has been given attention and could, for the first time, be explained. The mutual interaction of the shock pattern of the overexpanded flow and a recirculation region behind the shock seems to cause a short, asymmetric reattachment of the flow to the wall. Experiments and numerical simulations both show that this reattachment of the flow is resulting in the mentioned side load peak