Computational study of flow separation in truncated ideal contour nozzles under high-altitude conditions

Flow separation in rocket nozzles has been studied mostly under sea-level conditions, which fail to take into account changes in ambient density and ambient pressure during the flight of a rocket. In the present study, numerical analysis is conducted of flow characteristics within a truncated ideal contour (TIC) nozzle to investigate the influence of ambient density and pressure on flow separation. Six different altitudes from a typical flight are considered, from a very low altitude to a high altitude. The flow is analyzed by varying the nozzle pressure ratios corresponding to these altitudes. Both cold flow and hot flow simulations are conducted. The locations of separation positions at various altitude conditions are accurately captured and are found to be in good agreement with experimental results. The results of the study establish that for a given nozzle pressure ratio, the flow separation point is shifted upstream with increasing altitude. This clearly points to a dependence of separation position on the altitude of operation for TIC rocket nozzles.