On cavitation in thin liquid layers

A new apparatus is described, which allows events occurring within a thin liquid layer while being dynamically loaded in tension to be viewed. Experiments were carried out with water layers of initial thickness of ca. 100 urn and ca. 10 ^im. With the 100 |im layers, the observed mechanism was that of cavities' nucleation and growth. A model is proposed for the mechanism of cavity inception and growth which is based on comparison between the rate of gas ejection into the cavities and the rate of total volume increase. Using the experimental results, this model enables calculation of the 'evaporation constant'. Once the number density of cavities is fixed, and they begin to grow, a simple model of liquid volume conservation can be applied to describe the cavities' growth. The disintegration of the cavities' structure seems to be caused by air flow from the rim of the layer towards its centre. With the 10 u.m layers, the yield mechanisms are different and resemble, to some degree, the brittle fracture of solids. The yielding of the liquid occurs within a few microseconds, and later time effects are caused by surface tension acting on the already separated parts of the liquid.