Effect of Hydrofoil Shapes on Partial and Transitional Cavity Oscillations

The effects of foil geometry on partial and transitional cavity oscillations were examined by experiments. The transitional cavity oscillation can be observed in the upstream pressure fluctuation for all foils and the amplitude of oscillation becomes larger when the maximum cavity length becomes larger than about 75% of the chord length. The Stroulal number based on the chord length correlated with the value of a parameter $σ∕2α$ and increased from 0.07 to 0.17 with the increase of $σ∕2α$ from 2.0 to 6.0 for all foils. For thicker foils, the partial cavity oscillation could not be detected in the upstream pressure fluctuation. However, semi-periodical cavity shedding corresponding to the partial cavity oscillation could be visually observed for all foils and the Strouhal number based on the mean cavity length was about 0.15–0.35 for all foils. Thus, the effect of foil geometry appears only in the strength of partial cavity oscillation.