Computational Fluid Dynamic Analysis of AxWJ-2 Propulsor Cavitation Breakdown

Open Access
Author:
Peña, Christopher
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Jules Washington Lindau V, Thesis Advisor
  • Robert Francis Kunz, Thesis Advisor
Keywords:
  • Cavitation
  • CFD
Abstract:
For waterjet systems operating in marine ships, cavitation is a phenomenon that often occurs. The presence of vapor in the flow affects the performance of the pump and as the cavity grows the pump efficiency drastically reduces to a level where the pump cannot operate normally. Due to this influence on the pump performance it is of main interest to be able to predict the behavior of the cavitation process. At Johns Hopkins University and the Naval Surface Warfare Center Carderock Division (NSWCCD), researchers have designed, fabricated, and tested an axial flow waterjet pump (AXWJ-2). Measurements of the total head rise and shaft torque on flow through the pump have been taken at a range of flow conditions through cavitation breakdown. The aim of this thesis is to compare and analyze the results of the AXWJ-2 experiment with a numerical cavitation model. The numerical model applies a Reynolds-Averaged Navier Stokes method. The flow solver uses a locally homogeneous multiphase approach coupled with a liquid-vapor mass transfer model. Numerical solutions appear to accurately capture the integrated performance at all conditions. Results start to deviate at low tunnel pressures due to choking cavitation since the experiment includes decreasing flow rates while the CFD keeps a steady flow rate. Choking is seen to occur due to saturation of low pressure at the exit of the rotor passageway.