Abstract
Gas cavities, natural and ventilated, can occur on ship propulsors, control surfaces and hulls. These cavities can be significant sources of small bubbles in the ship wake. We present a two-dimensional time resolved X-ray densitometry system developed for investigation of natural, ventilated and mixed cavities. First we consider the limitations and performance of our X-ray system, and compare the measured void fraction to stationary known void fraction, and to data for a ventilated cavity obtained using dual fiber optical probes. Second, we present preliminary data from time-resolved X-ray used to observe the overall dynamics and time dependent void fraction distribution of a cavitating backward facing step with and without gas injection.