Cavity shape measurement on propeller blade surface by combination line CCD camera measurement method

A new combination-line-CCD camera method has been developed to accurately measure three-dimensional propeller blade cavitation shapes and volumes, which strongly correlate with pressure fluctuations. The effectiveness of this system was validated through model experiments conducted in NMRI's large cavitation tunnel using a propeller for a 749GT coastal vessel. The accuracy was verified by comparing the estimated pressure fluctuation, derived from the cavity volume, with the pressure sensor measurements. In the estimation, the unsteady cavity is replaced by a moving spherical bubble with a varying radius, and the pressure fluctuation induced by the sphere is calculated. Applying the proposed method to the experimental cavity shape data yielded pressure fluctuation estimates that closely matched the pressure sensor measurements. This result demonstrates the strong correlation between the time variability of the cavity volume and the pressure fluctuation induced by cavitation in the model tests.