Cavitation phenomenon research for different flow conditions

Cavitation is a multiphase phenomenon including vapor bubbles creation and collapse occurring alternately at high frequency in liquid stream. Creation of bubbles is possible under low pressure conditions, which occur for example during acceleration of the liquid. The collapses of bubbles generate pressure waves which spread through the flow. Working under cavitation condition is especially dangerous for power machines such as pumps and turbines, because it can lead to serious damage of blades. To investigate cavitating flow over a foil a test rig was built. The test rig included chamber with the blade fixed to the disc that enabled to set different angles of attack. The flow rate of water was changed by means of pump’s motor variable frequency drive. As the flow rate was increased, the velocity in chamber rose and pressure dropped. This led to cavitation structures appearance and development on the suction side of the blade. For different flow conditions the pictures of cavitating flow were taken and examined. Moreover, the pressure and the inlet and outlet of the chamber were recorded, as well as the value of volumetric flow rate. That enabled to determine the cavitation number, a parameter that describes intensity of cavitation in the flow, for each case.