Numerical Investigations of the Base-Flow Characteristics of Axisymmetric Aerospike Nozzles

抄録

The base-flow characteristics of aerospike nozzles are discussed based on the results of numerical simulations. The nozzle is truncated at a 20% portion of the isentropic length, and the condition both with and without external flow is considered. The computed results realize that the ambient pressure influences the base pressure when the pressure ratio is low and becomes independent from the ambient pressure when the pressure ratio is high, as pointed out in previous studies. Although the ambient pressure is mainly transferred to the base region by the envelope shock wave, some computed cases show that the ambient pressure is not transferred to the base surface even when the envelope shock wave impinges on the subsonic part of the base region. Two high-pressure regions, one created by the shear layer impingement of the nozzle exhaust flow and the other by the envelope shock wave impingement, appear on the nozzle axis. The flow stagnates either of the higher pressure regions of these two, and the strong reverse flow toward the base surface occurs. The ambient pressure is transferred to the base surface when the flow stagnates at the high-pressure region created by the envelope-shock impingement on the nozzle axis. It occurs when the pressure ratio is low. The base pressure becomes independent from the ambient pressure when the stagnation point changes to the shear-layer impingement on the nozzle axis. It occurs when the pressure ratio is high.