Achievements and challenges in cavitation research on ship propellers

Abstract

This paper reviews cavitation research on ship propellers performed in the recent past in MARIN’s Depressurized Towing Tank and cavitation tunnels. Cases are presented through which advances have been made possible in the design of propellers and ships, and unresolved issues are discussed that form the challenges of future research. Our focus is on inception, hull-pressure fluctuations, and erosion on propeller blades and rudders. Cavitation occurs on nearly all ship propellers. It may lead to expensive problems if not acknowledged in an early design stage. The two most frequently occurring problems are noise and vibration in the afterbody due to cavitation-induced pressure fluctuations on the hull, and cavitation erosion on propeller blades and appendages. Early recognition of these adverse effects is important, not only to ensure compliance with contract requirements, but also because often cavitation has to be controlled at the cost of propeller efficiency. To ensure that the propulsor meets the requirements relating to comfort (vibration and noise) and safe and economic operation (erosion), model scale experiments or computations addressing cavitation are conducted prior to construction. As reliable computational techniques that incorporate all aspects of cavitation that relate to noise, vibration and erosion are lacking, scale model experiments are still the preferred choice. From experiments in the first cavitation tunnel, built by Parsons in 1895, insights were built up as to how one should model cavitation phenomena to allow for full scale predictions. This has led to the use of medium sized cavitation tunnels in the mid nineteen hundreds and eventually to the large cavitation tunnels of today which allow for complete ship models to be installed in front of the propeller. At the Maritime Research Institute Netherlands (MARIN) propeller cavitation behavior is investigated in the Depressurized Towing Tank (DTT) which allows for the testing of large scale ship models in the presence of a free surface. The DTT is in operation since 1972 [19] and has been modernized in 2001. A medium sized cavitation tunnel and a small high