A Numerical Study of Wake Behavior in Plug Nozzles

Plug or aerospike nozzles for rocket engines can be of interest in future spaceplane concepts because of their self-adapting capability at varying altitude. In that view, to make aerospike nozzles fully exploited, the flowfields generated in these nozzles need to be better understood. In particular, one of the aspects of the flowfield that has to be still analyzed in depth is the behavior of the wake that takes place behind the truncated base of the plug, and its actual contribution either positive or negative to engine thrust. In this paper, a study of the base pressure and of the main flow features affecting its behavior is carried out by a validated numerical code to solve turbulent Navier-Stokes equations, based on the fitting of flow discontinuities. The results point out the flow features affecting the base pressure and its evolution for varying ambient pressure, and the differences of the flow structure between operations in still air and actual operations in supersonic flight.