Numerical Simulations of the Cavitating Flow on a Marine Propeller

ABSTRACT This paper deals with numerical simulations of the cavitating flow around a marine propeller operating in open water but mounted on an inclined shaft. The investigation is mainly based on both Large Eddy simulation (LES) and Unsteady Reynolds-Averaged Navier-Stokes (URANS) in combination with a Volume-of-Fluid implementation to capture the liquid-vapour interface and a transport equation-based method for the mass transfer between the phases. Potential flow solver result will also be included to offer a complete picture of the general behaviour and capabilities of a range of computational methods with different levels of detail. Highspeed video recordings from experiments are available for detailed inspection. INTRODUCTION Propeller cavitation is of major concern for vessels in terms of performance degradation, erosion and passenger comfort due to cavitation induced vibrations and noise. However, with increasing demand for faster vessels, and at the same time, for higher propulsive efficiency, it is favourable to decrease the margin of cavitation-free operation or to allow for some "controlled" amounts of sheet cavitation on the propeller blades. These two contradictory demands cause the propeller design to be a game of balancing the pros and cons, and it becomes crucial to be able to determine the characteristics of cavitation and not only its appearance or extent. A common way to study propeller cavitation is through model scale experiments. However, this method has several drawbacks, such as high cost, long execution time, scaling effects, and perhaps more importantly, the limited measurable data that can only indicate the possible existence of a certain problem and will give more limited guidance regarding how to redesign. All these constraints have cultivated the need for developing a reliable, versatile and robust computational tool, to better understand the phenomenon itself as well as to contribute in advanced prediction and design work. Today the standard design tools typically include potential flow solvers on the basis of lifting-line/lifting surface theory, able to predict a reasonable pressure distribution on the blade, but with clear theoretical limitations regarding cavitatio