Methodology to Solve Flowfields of Plug Nozzles for Future Launchers

Abstract

In the development of future launchers, in particular Single Stage to Orbit (SSTO), the use of plug nozzles looks promising because of the possible improvement of performance, and therefore a capability to achieve accurate evaluations of the relevant flowfields is required. Nevertheless, due to the typical flow features, analyses performed by the common Computational Fluid Dynamics (CFD) methods lead to uncertain and time consuming results. To circumvent some of these problems, an approach based on a simple simulation model that replaces the mixing layer between nozzle jet and external flow by a contact discontinuity, was recently proposed by the authors. Following this approach, the complex calculation of the turbulent mixing of flows having different thermodynamic characteristics can be avoided, while correctly accounting for the main features of the flowfield. In this paper, this simple model has been implemented to compute linear plug nozzle flowfields at different ambient conditions and for different geometries of the plug. The expected flow behavior has been well reproduced and good agreement with the theoretical nozzle performance has been achieved, thus allowing to carry out a performance analysis for some of the main characteristic parameters.