Simulation of swirl in rocket nozzles at off-design pressure ratios

In this investigation, computational fluid dynamics simulations are employed to examine the effect of swirl on the flow field within a rocket nozzle. A fifteen degree, conical nozzle serves as the computational domain while the operating conditions at the inlet will contain swirl of varying strengths, while the outlet pressure is varied to produce a range of pressure ratios. The relative strength of these swirl velocities is varied using the revolutions per minute setting at the nozzle inlet. Pressure and velocity results are evaluated throughout the nozzle with particular attention paid to the location and strength of the shocks at the centerline and the nozzle wall. Results indicate that swirl has a minor effect on the shock strength in the diverging or supersonic portion of the nozzle while having a more pronounced effect upstream of the throat. The wall chamber pressure in the subsonic region is significantly increased in comparison to the non-swirling case.