Numerical Simulation of Propeller Cavitation in Non-Uniform Flow Fields

Cavitation is a phenomenon with intense vaporization of liquids which happens when local static pressure of liquid falls below the critical pressure threshold. Cavitation contains most of the complex flow in fluid dynamics and the comprehension we have is still limited. Modern ships face the challenge of high speed and other performance loss including thrust reduction, noise and vibration caused by cavitaion. The stern flow field of propeller is not simple uniform flow, instead it is non-uniform flow. Therefore, it is necessary to study the cavitation and hydrodynamic characteristics of propeller under non-uniform velocity field conditions.

To study the cavitation characteristics of propeller experimentally is both time and resource consuming. Hence the main attention of present work is to numerically investigate the simulation of propeller cavitation in non-uniform flow field. The numerical results can be used as a reference to evaluate the working ability of a propeller in case of actual nevigation. Typical unsteady dynamics are predicted by the RANS method with a modified shear stress transport (SST) k-ω turbulence model. The numerical results such as cavitation shape, pressure distribution, the thrust coefficient Kt and the torque coefficient Kq are analyzed and compared with each other, to study the influence of non-uniform flow.

All the simulation calculations of open water characteristics of propeller are obtained using InterPhaseChangeDyMFoam in the open source CFD software platform OpenFOAM with Schnerr-Sauer cavitation model. In order to reduce the calculation cost, the direct simulation of non-uniform incoming flow is adopted as the working condition parameter in the smulation process. The numerical results in open water of standard E779A propeller are basically in accordance with experimental data, indicating the reliability of the present method. It is found that the propeller under non-uniform flow output less thrust, and the unsteady characteristics of the sheet and tip cavitation on the propeller surface become more obvious. The disturbance of cavitation flow to pressure variation is also the reason for the reduction of propeller thrust coefficient. With the change of advance coefficient, this influence will be strengthened.