Multi-dimensional modelling of multiphase flow physics: high-speed nozzle and jet flows - a case study

Multi-dimensional modelling of multiphase flows has become more prevalent a s computer capabilities have significantly expanded. Such analyses are nece ssary if the flow physics demonstrates behavior that is fundamentally diffe rent from the estimates of one-dimensional analyses. Multiphase multi-dimen sional behavior may involve physical mechanisms that interact with the flow field transverse to the main fluid direction and feedback into downstream processes. Consider the physics of high-speed internal nozzle flow, downstr eam external jet flow and the dynamics of jet breakup. This is a prime exam ple of a coupled problem where multi-dimensional aspects may need to be con sidered. This paper examines multiphase physics as an illustration of the c onditions under which multi-dimensional modelling would be required. Intern al nozzle flow can involve cavitation phenomena, and as the geometry become s more abrupt or asymmetric, multi-dimensional modelling is required. High- speed simulations using our internal flow model, CAVALRY, indicate that cav itation behavior can become oscillatory as the nozzle shape is altered. Thi s exiting internal flow emerges as a multi-dimensional external jet flow, w hose downstream breakup can be noticeably influenced by the inlet condition s as well as the jet breakup mechanisms. Jet breakup models first developed for the TEXASV model are utilized in the multi-dimensional KIVA code simul ations for gas-liquid flows. The simulation results suggest that similar je t breakup mechanisms are operative for a multi-fluid system. Our comparison s to particular sets of data for high-speed nozzle flow and jet breakup in a gas suggest that the approach can be extended to multiphase systems using similar concepts; i.e. TEXAS-3d. (C) 2001 Professor Michael Corradini. Pub lished by Elsevier Science B.V. All rights reserved.