Experimental Study on Flow Transition in Dual Bell Nozzles

The dual bell nozzle is a concept of altitude adaptive nozzles. The flow adapts to the altitude by separation at the wall inflection at low altitude, and full flowing at high altitude. To understand the phenomenology of the flow by the transition from sea level to high altitude mode, a series of tests have been made at the cold flow test bench P6.2 at DLR Lampoldshausen. Three nozzles with different geometries have been tested. Two of them were successively shortened and driven unter the same conditions for each extension length. This study yields the influence of the geometric parameters of the basis and the extension on the transition conditions. Furthermore a transition prediction is given.