Ph.D Thesis

Ph.D StudentYusupov Mor Marat
SubjectAnalysis and Solutions for Two-Phase Bubbly Nozzle Flow
and Their Application in Underwater Jet Propulsion
DepartmentDepartment of Aerospace Engineering
Supervisors PROFESSOR EMERITUS Alon Gany


The present work is a theoretical investigation of two-phase bubbly flows and their application to underwater jet propulsion. It includes various aspects, such as physical description and modeling, mathematical formulation, numerical simulations, analytical development, and application of the above investigation to the design of a water jet engine.

In this work the analytical approach is similar to that applied to single-phase, steady, quasi-one-dimensional gas flows. Introducing Mach number into the flow equations, we find novel, closed-form analytical solutions for specific cases including mass addition and wall friction.

The expressions obtained from the analytical approach, as well as the behavior of the flow, demonstrate a close analogy to those of classical, single-phase gas flows. The predictions of the analytical approximation were compared to numerical solutions. A unique, unconditionally stable numerical code was developed to provide solutions of high accuracy. The differences in most of the flow parameters did not exceed a few percent, thus indicating good agreement.

Substantial simplification of the design of a water jet engine was achieved by the use of analytical expressions. These yield a rather accurate first approximation, so that a final engine design optimization could be reached within a small number of iterations. Moreover, using a homogenous flow model and its analytical solution, the performance of the ideal water jet engine (maximum possible thrust and efficiency) could be readily evaluated.