Nucleation effects on cloud cavitation about a hydrofoil

The dynamics of cloud cavitation about a three-dimensional hydrofoil are investigated experimentally in tunnel with depleted, sparse and abundant free-stream nuclei populations. A rectangular planform, NACA 0015 was tested at Reynolds number $1.4\times 10^{6}$ , an incidence $6^{\circ }$ range numbers from single-phase flow to supercavitation. High-speed photographs shedding phenomena were acquired simultaneously unsteady force measurement enable identification cavity modes corresponding spectral peaks. analysed through decomposition the high-speed movies, revealing different instabilities according content. With no active nuclei, fundamental mode occurs Strouhal 0.28 is defined by large-scale re-entrant jet formation during growth phase, but shockwave propagation for collapse phase cycle. Harmonic subharmonic also occur due local tip shedding. For case, again much slower resulting frequency $St=0.15$ . harmonic forms this case two shockwaves; initial slow propagating wave followed second faster wave. passage first causes partial condensation leading lower void fraction consequent increase speed along larger-scale condensation. sparsely seeded flow, coherent fluctuations reduced intermittent, disperse activation breakup optimal condition maximum reduction lift.