Passive active control of cavitating flows around ship hydrofoils

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Cavitation negatively affects the performance of marine propellers, rudders, pumps, and other machinery as it is one of the major sources of erosion and energy efficiency lost. In this regard, cavitation control methods can help to improve the design of propulsion, and steering devices. Passive cavitation control methods were successfully used and are the preferable choice, because of the low costs. However, the mitigation and control of cloud cavitation for severe cavitation regimes (e.g., dynamic positioning of wind offshore supply vessels) can hardly be achieved using only a passive control methods. On the other hand, using only active control methods for different cavitating regimes requires extra energy and, consequently, leads to higher costs. Therefore, a combined passive-active control methods are the preferred choice to efficiently suppress cavitation for a broad range of cavitation regimes and reduce costs. For this aim, the active control method is only used for the severe cavitation regimes, where the passive control method is not able to control cavitation. In this project, we intend to develop a passive-active control method by using miniature vortex generators placed on the hydrofoil surface and a combination of discrete quasi radial jets (water injection). First, we will extend and validate an existing multi-scale Euler-Lagrange method to take into account compressibility of the cavitating flow. Second, we will perform systematic numerical investigations using the extended multi-scale Euler-Lagrange method (based on PANS-equations). Varying the positions of the miniature vortex generators and the injection rates, the optimized configuration of the proposed control method will be determined to suppress cavitation and mitigate its negative effects. We will then perform systematic experimental investigations in our cavitation tunnel using high-speed imaging, force and pressure sensors, and hydrophones together with advanced processing procedures and data analysis methods.