FLOW SEPARATION IN OUT-OF-ROUND NOZZLES, A NUMERICAL AND EXPERIMENTAL STUDY

The start-up and shut-down transient phases in rocket engine nozzles generate high side loads. The internal and external flow fluctuations can excite the eigenmodes of the nozzle structure. The flow separation in out-of-round nozzle intensifies the initial structural deformation, leading in worst case, to the collapse of the nozzle. In the framework of the DLR internal cooperation program ProTAU, the ovalization of nozzles is being investigated from both the numerical and the experimental point of view. Three nozzle geometries have been designed and deformed applying various methods. The flow behavior in the initial axisymmetric and the obtained ovalized contours has been numerically investigated. The most promising contours will be manufactured as permanently ovalized nozzle models and tested under cold flow conditions.