Microbubble disperse flow about a lifting surface

The effect of freestream nuclei content on stable cavitation about a hydrofoil and subsequent microbubble production in the wake is investigated experimentally. Microbubble concentrations are measured upstream and downstream of the hydrofoil for four upstream nuclei concentrations and three cavitation numbers. For each case the number of activated nuclei on the hydrofoil and the transverse distribution of concentrations in the wake were measured. Upstream nuclei concentrations were measured with interferometric Mie imaging in the size range between 45-250 µm at concentrations up to 30 cm⁻³. Wake microbubble concentrations were measured using shadowgraphy in the size range 5-50 µm at concentrations up to 600 cm⁻³. Wake concentration were found to increase for small changes in low upstream nuclei concentrations but to then decrease for further increase in concentrations. Wake concentrations were found to generally increase with decrease in cavitation number for a particular upstream nuclei concentration. The increase in wake bubble concentrations with seeding increase, at the high cavitation number, is in the smaller bubble size range whereas the increase at the lower cavitation numbers occurs over a greater size range.