Cavitational Flows / the Geometry of a Supercavitation Bubble

Cavitation, i.e. the appearance of vapor cavities inside an initially homogeneous liquid medium, occurs in different situations commonly characterized by the pressure decrease below the vapor pressure of the liquid. The vapor structures are often unstable, and when reaching a zone of increased pressure, they may violently collapse. Thus, at a first glance, cavitation appears as a harmful phenomenon that should be avoided. The Russians were the first to identify a positive implication of cavitation, called supercavitation, and built a torpedo based on this technology. As the cavitation parameter decreases, a small cavity attached to an underwater body will extend and grow longer and longer, enveloping the entire body. Its overall drag with the surrounding will decrease significantly. Understanding the geometry of a supercavitation bubble is essential to the design of supercavitational underwater vehicles and applications. In a series of experiments we have investigated the development and shape of supercavitation bubbles under various operating conditions and different cavitators. Using a new theoretical approach we have examined the bubble shape and its stability for different geometries and disturbances. The research brings new insight for the phenomena of supercavitation bubbles.