Diffusion Induced Bubble Populations Downstream of a Partial Cavity

Bubble populations downstream of stable partial cavities were examined using in-line holography, and the bubble number distribution and void fraction of the bubbly clouds were determined. The measured flux of bubbles downstream of the cavity was used to determine the diffusion rate of noncondensable gas into the cavity. Four models of gas diffusion into partial cavities from Parkin and Kermeen (1963), Brennen (1969), and Parkin and Ravindra (1993) are reviewed, and their predictions are compared with the experimentally determined mass diffusion rates. The models, which recognize a turbulent boundary layer over the cavity interface, over-predict the diffusion rate by one order of magnitude for cavities characterized by L/δ > 25.