Advances in Cavitation Measurement Techniques: Shape and Bubble Size Distribution Analysis

Cavitation occurring on propellers operating in ship wakes adversely affects vessel performance through hull vibration, thrust reduction, and erosion. With underwater radiated noise from ships under discussion at the International Maritime Organization for marine environmental protection, cavitation has been identified as a primary noise source. Accurate cavitation prediction methods at the propeller design stage require accumulating experimental data through model propeller tests. Quantitative evaluation of cavitation volume and bubble size distribution is particularly needed, as these parameters strongly correlate with pressure fluctuation and underwater radiated noise generation. This study presents two advanced cavitation visualization techniques developed to address these measurement requirements. First, a multi-view line sensing technique enables three-dimensional capture of tip vortex cavitation geometry, providing macroscopic cavity shape measurements. Second, a shadowgraph visualization method using a transparent airfoil model allows detailed observation and quantitative analysis of individual bubble characteristics, including bubble size distribution measurements. These complementary measurement techniques provide comprehensive characterization capabilities ranging from macroscopic cavity geometry to microscopic bubble properties. The developed methods contribute to improved cavitation prediction accuracy and support the development of quieter, more efficient marine propulsion systems.