Flow separation study in stiff ovalized rocket nozzles, Part I: experimental approach

During the transient startup and shutdown process of a rocket engine high side loads occur, due to unsymmetrical flow patterns. The resulting deformation, and its retroactive effect onto the internal flow, excite the nozzle structure and can lead to its fatal damage. Flow separation at the nozzle wall amplifies the deformation. To investigate and predict the effects as well as the underlying mechanism that cause these phenomena, the flow characteristics in ovalized nozzles are investigated in the DLR project ProTAU. In this paper CFD results of ovalized TIC nozzles are presented and compared to experimental data, to validate the used numerical method. The presented results show good overall agreement for the relevant regimes, with a tendency to slightly overpredict the separation position. In the consecutive step the method will be extended to simulate the coupled problem of flow structure interaction.