Some Experiments With Specific Types of Cavitation on Ship Propellers

The influence of the boundary layer and of the nuclei content of the fluid on cavitation inception is investigated. Two models of ship propellers, displaying sheet cavitation and bubble cavitation respectively, are used. Generation of additional nuclei is obtained by electrolysis. It is shown that nuclei are necessary to create sheet cavitation when the laminar boundary layer separates. When the boundary layer is laminar, however, the absence of sheet cavitation is very persistent and independent of the nuclei content. Application of roughness at the leading edge of the propeller blades generates sheet cavitation independent of the nuclei content. Bubble cavitation is strongly affected by the nuclei content of the water. Roughness at the leading edge can indirectly affect bubble cavitation when nuclei are generated by the roughness elements.