Cavitation occurs in liquid flows in which the pressure is locally below the vapor pressure. This leads to the formation of gas bubbles (vaporization of the liquid). A subsequent pressure increase downstream causes the bubbles to implode, which generates high velocities and temperatures. Material erosion can happen if this process occurs close to the wall, which significantly reduces the service life of affected components. The processes surrounding this phenomenon are still not fully understood and are the subject of numerous scientific studies.
The hydro-laboratory of the University has a test rig to visualize and investigate flows affected by cavitation. Investigations were recently carried out on a hydrofoil with a NACA0012 profile. A high-speed camera was used to visualize the phenomenon of cavitation. Two types of cavitation can be observed. The accelerated flow at the tip gap leads to gap cavitation and the pressure drop behind the leading-edge leads to surface cavitation on the top of the blade.
Computational fluid dynamics (CFD) is crucial during the development process to reduce the costs of expensive prototype testing. Experimentally obtained data are needed to validate and improve the models describing cavitation processes.