Design Modifications to Minimize Tip Vortex Cavitation in Marine Propellers

Abstract Underwater radiated noise (URN) from marine vessels poses significant threats to marine ecosystems, necessitating effective mitigation strategies. Propellers are a primary source of this noise, and reducing their emissions is essential for quieter ship operations. Cavitation, the vaporization of liquid water in low-pressure regions forming during the operation of propellers, is one of the major contributors to propeller noise. Among various forms of cavitation, the onset of sheet cavitation is delayed on modern propellers by the improvements in blade design, causing tip vortex cavitation (TVC) to often appear earlier. The current study focusses on mitigating TVC through geometric modifications of the propeller blades. The blade geometry is fine-tuned through bending and twisting; bending is performed in the direction normal to the blade’s sectional chord-lines, altering its rake and skew distribution. Twisting is applied through modification of the radial pitch distribution. In this work, a computational toolbox - MultiProp, is developed to transform conventional propeller geometries into modified designs based on specified bending and twisting parameters. An integrated performance index (IPI) is proposed, combining TVC behavior and hydrodynamic efficiency to assess propeller performance. Numerical simulations comparing conventional and modified propellers reveal that these geometric changes effectively mitigate TVC without compromising hydrodynamic performance. The proposed modifications can be incorporated during the design stage as a passive TVC mitigation strategy, forming the basis for a multi-objective optimization framework to design efficient, low-noise propellers.