Photographs of different types of cavitation

Partially Cavitating Hydrofoil

Here we see a hydrofoil exhibiting partial cavitation. A hydrofoil is a "lifting" surface. It is like an airplane wing in that it provides lift when a fluid flows past it. Both an airfoil and a hydrofoil create lift by creating a low pressure on the upper surface. In the case of the hydrofoil though, the pressure can become so low that the liquid water transforms into a gaseous water (cavity). The study of cavitating hydrofoils is important for research in the propulsor industry because a propeller is nothing more than a few hydrofoils "wrapped around" a hub.
Click for a close-up of a sheet cavity.

Partially Cavitating Propeller/Tip Vortex Cavity

This propeller is also exhibiting partial cavitation. The amount of cavitation that occurs on the blade usually depends on the position of the blade in it rotation. Usually the most cavitation occurs when the blade is near the top of its rotation. Research in this field is important because cavitation can cause excessive vibrations, noise, and degredation of the propeller blade. The efficiency of a propeller will also be compromised. Notice the thin string-like cavity near the tip of the blade. This is called a (developed) tip vortex cavity

A Walk in the Clouds

This hydrofoil exhibits "cloud cavitation" Cloud cavities present modeling difficulties because they tend to be unstable. It is also difficult to hydrodynamically model the flow around a "cloud".

Bubbles!

This foil exhibits a fairly clean "sheet" cavity. Although near the end of the cavity, you may notice some "bubble" cavitation. Notice that the cavity does not begin at the leading edge of the foil. (The leading edge is the very front of the foil.) Efforts are underway to correctly model cavitating propellers with non leading edge detachment.

It's a bird! It's a plane! It's SuperCavity!

Here we can see a hydrofoil undergoing "super cavitation"--the granddaddy of all cavities! A partial cavity becomes a super cavity when it extends beyond the end of the foil (or blade in the case of propellers).

It's my Dream

This cavity is a clear example of sheet cavitation. Sheet cavities are a hydrodynamicist's dream come true. They present the least modeling difficulties.

It's my Nightmare

This hydrofoil is exhibiting a rare form of cavitation. Notice that there are two cavities on the foil. This is the hydrodynamicist's nightmare. The cavity near the leading edge of the foil forms and then collapses quickly. Then, a "mid-chord" cavity forms at about halfway down the hydrofoil. It is possible to model mid-chord cavities or leading edge cavities alone, but a combination of the two has not yet been attempted by our research group.

Hub Vortex

This photograph shows a cavitating propeller. You can clearly see the tip-vortex cavities. Also present is a "hub-vortex" cavity originating from the tip of the hub of the propeller. Research on these forms of cavitation is underway.

Shark Attack

Here is a partially cavitating eliptical hydrofoil. This hydrofoil shape is one step closer to an actual propeller blade.