Robert F. Kunz

COMPUTATION OF COMPRESSIBLE MULTIPHASE FLOWS

A computational model capable of capturing fully compressible multiphase flow including energy conservation is presented. The model is a finite volume form based on the Reynolds Averaged Navier-Stokes Equations and is capable of considering fully general equations of state. The preconditioning matrix is presented and ensures a well conditioned eigensystem, essential for efficient and accurate multiphase computations. Solutions are given representing both the utility of the preconditioning method as well as the ability of the model to capture highly compressible multiphase flow fields. When considering compressible flows where thermal effects are significant and a general equation of state is necessary, energy conservation in a multiphase flow field is shown to be a requirement.

The Immersed Boundary Method for Water Entry Simulation

Adaptation of the direct-forcing immersed boundary method for the simulation of multiphase flows is examined and the difficulties arising due to large density ratios are discussed. The importance of satisfaction of boundary conditions at the immersed body surface is addressed and demonstrated both analytically and in numerical simulation. Simulation of free surface water entry for 2-dimensional square and circular cylinders is performed and resulting pullaway times and cavity shapes are shown. Results for simulation of 3-dimensional spheres are compared to experimental data. Difficulties in using the implemented method for certain types of simulation, such as 2-dimensional axisymmetric cases are discussed, along with strategies to alleviate these in the future.