Cavitation in Hydraulic Machines: Mechanisms and Effects

This lecture focuses on cavitation in hydraulic machines, a critical phenomenon affecting turbomachinery design. It begins with a definition of cavitation, describing it as the formation of vapor-filled cavities in a liquid due to pressure drops without heat exchange. The instructor explains the conditions for cavitation occurrence, emphasizing the importance of pressure coefficients and cavitation numbers. The lecture details the effects of cavitation, including performance degradation, noise, vibration, and erosion of machine components. Various types of cavitation are discussed, such as bubble cavitation, leading edge cavitation, and vortex cavitation, each with distinct characteristics and implications for machine design. The instructor also highlights real-world applications, including the challenges faced by high-speed vessels and the natural occurrence of cavitation in marine life. Experimental methods for studying cavitation erosion are presented, showcasing techniques like ultrasound cavitation tests. The lecture concludes with a discussion on the significance of understanding cavitation for engineers and the ongoing search for materials that can withstand its effects.