Discussion on the Development of 3D, Multiphase Solvers for Problems in Solid Rocket Propulsion

Abstract

A discussion on the ongoing development of multiphase solvers for addressing computational problems in solid rocket propulsion will be presented. The working substances of solid rocket motors are typically non-homogenous and are comprised of multiple phases. Some of the combustion products condense into particles in the flow field while others are gaseous. As a result, the working substance is essentially a suspension of condensed combustion products (CCP) in hot gases. Due to this, a number of complex physical phenomena are introduced in the flow field inside the rocket, which cannot be visualized by using a simple single-phase Navier Stokes solver. Therefore, for realistically capturing the flow features in a rocket, a 3D multiphase flow solver is required. The ongoing work is aimed at developing and testing multiphase solvers which would be capable of predicting the flow features and performance parameters of solid rocket motors. A family of solvers is being developed which can capture the interaction of multiple phases. Here, the word "phase" denotes chemically or physically distinct substances which may need be be modelled separately. The solvers have been developed in FORTRAN. The spatial discretization of the governing equations has been done by using the unstructured finite volume method. The solvers have been developed for tetrahedral meshes. Integration in time is done using the explicit Range-Kutta 4 stage method. The Euler-Euler or Multi-fluid model for multiphase modelling is used. This model states that all "phases" in the flow can be approximated as interpenetrating continua and that the interactions between the phases can be modelled by the means of certain constitutive equations, such as that of fluid drag. The multiple components co-permeate in the domain as fluids, i.e., they're able to occupy the same space simultaneously. The objective of these solvers is to provide a means to estimate the thrust losses and salient flow features introduced by the multiphase nature of the flow field inside a solid rocket motor. However, the solvers developed are largely generic and may be adapted to several other multiphase problems by making minimal problem specific modifications. In this work, we intend to discuss the governing equations, constitutive equations and the models and methods used for the development of our solvers.