Unified Flow Solver for transient high altitude events with mixed continuum and rarefied flows

CFDRC proposes to develop a computational tool for transient, high-altitude events with mixed continuum and free molecular flow regimes. The proposed technology builds upon the Unified Flow Solver (UFS) previously developed by CFDRC, which will be leveraged with several new features for transient chemically reacting two-phase, gas-particle flows interacting with multiple bodies in relative motion under mixed continuum-rarefied regimes. The new tool will incorporate several innovations: i) octree Cartesian mesh for automatic mesh generation and dynamic adaptation to transient flow properties and moving bodies, ii) a cell-by-cell automatic selection of Boltzmann and Navier-Stokes solvers based on continuum breakdown criteria, iii) kinetic models for two-phase rarefied flows, iv) kinetic and fluid models of chemical reactions. In Phase I, we will demonstrate UFS for high-fidelity characterization of short duration propulsive/detonative events in mixed continuum/rarefied flows and illustrate its advantages for simulation of unsteady effects. New capabilities for two-phase flows, chemical kinetics in fuel rich environments, and generalized 6 degree-of-freedom hard body interactions will be added. In Phase II, we will fully develop an advanced, high-fidelity simulation tool for high altitude, transient propulsive/detonative events. Numerical studies will be conducted to address specific components of the new tool for problems of interest to the Army.