Parallel AMR scheme for turbulent multi-phase rocket motor core flows

The development of a parallel adaptive mesh refinement (AMR) scheme is described for solving the governing equations for turbulent multi-phase (gas-particle) core flows in solid propellant rocket motors (SRMs). The Favre-Averaged Navier-Stokes equations are solved for the gas-phase. Turbulence closure is achieved by using a two equation turbulence model. An Eulerian formulation is used to describe the motion of the inert, dilute, and disperse particle-phase. A cell-centred upwind finite-volume discretization and the use of limited solution reconstruction, Riemann solver based flux functions to determine the inviscid flux for the gas and particle phases at cell interfaces. Green-Gauss integration over the diamond-path defined at cell interfaces is used to determine the primitive-variable gradients for evaluation of the viscous fluxes. A parallel multigrid method coupled with an explicit optimally-smoothing multi-stage time-stepping scheme is used to obtain steady state solutions. Unsteady calculations are achieved through the use of a dual time-stepping approach. The propagation of the propellant-core flow interface is tracked using the level set method and a mesh adjustment scheme is used to fit the computational mesh to the location of the burning interface. Application of block-based AMR accurately resolves the multiple solution scales of the fluid flow and enables efficient and scalable parallel implementations on distributed memory multi-processor architectures. High-scalability of the model has been achieved on a parallel cluster computer consisting of 276 processors. Various numerical test cases are presented to verify the validity of the scheme as well as demonstrate the capabilities of the approach for predicting SRM core flows.