Influence of External Flow on Plume Physics of Clustered Linear Aerospike Nozzles

摘要

The influence of external flow on the plume physics of cell nozzle flows and the cell base wake behavior of simplified clustered linear aerospike nozzles were characterized using surface pressure measurement, flow visualization using the background oriented schlieren method, and theoretical modeling. The test model comprised three or four clustered cell nozzles, or a nonclustered two-dimensional nozzle with a designed Mach number of 3.5, and was connected to a straight section followed by a straight ramp inclined at 12 deg. In the cases with or without external flow, the measured pressure distributions on the surface of the test model were found to be different in the presence of external flow: The ramp surface pressures were maintained at a certain level above the environmental pressure according to the cell nozzle flow conditions, whereas the pressure distributions in the cases without external flow demonstrated highly periodical compression/expansion features. The results of flow visualization indicated that the pressure maintained on the ramp surface depends mainly on how the external flow controls the jet expansion by forming a slip surface. The cell base wake was found to behave as a closed wake in the presence of external flow. Those pressure behaviors were successfully predicted using the physics-based theoretical models established in this study.