Efficient Numerical Methods for Waves in One-Dimensional Two-Phase Pipe Flows

摘要

This thesis is aimed at improving simulation efficiency for stratified-wavy gasliquidudflows. Towards this goad, the simpler nature of incompressible two-phaseudflows is utilized for predicting hydraulic wave dynamics, both through theoreticaludanalysis and numerical simulation. Numerical methods proposed for the incompressibleudtwo-fluid model includeud a hybridization of a finite volume method with analytical roll-wave profileudsolutions,ud a Method of Characteristics and finite volume hybridizations thereof, andud a linearized Riemann solver (Roe scheme.)udTheoretical analyses based on the same model further the understanding of Kelvin-udHelmholtz stability in stratified pipe flows and provide a comprehensive accountudof how the flow stability predictions of numerical simulators depend on model discretization.udKelvin-Helmholtz/von Neumann analysis is shown to be a valuableudsupport tool for choosing numerical scheme and simulation parameters. Finally, auddual grid scheme is proposed which enables us to extend the computational benefitsudof incompressible flow models to compressible systems. The dual grid schemeudeffectively decouples the length scales and numerical CFL restrictions of hydraulicud(incompressible) waves from that of acoustic (compressibility) waves. Efficiencyudis observed to be improved by several orders of magnitude for a wide range ofudsimulation cases.