Cavitation

Cavitation is a phenomenon that arises due to pressure fluctuations in liquid fluid systems and leads to serious problems in engineering applications. This phenomenon, particularly observed in hydraulic pumps, turbines, and propeller systems in the maritime industry, results in critical consequences such as material erosion, energy loss, and reduced system efficiency.

The fundamental mechanism of cavitation lies in the local pressure of the liquid dropping below its vapor pressure, causing instantaneous vaporization followed by the collapse of bubbles in high-pressure regions. Although this dynamic process occurs at a microscopic level, it produces destructive effects on a macroscopic scale.

Cavitation refers to the sudden collapse of vapor bubbles formed when the pressure within a liquid drops below its vapor pressure, along with the mechanical damage caused during this process. This phenomenon particularly leads to performance loss and material erosion in hydraulic systems such as pumps, turbines, and propeller systems.

The boiling point of water is directly proportional to pressure. As pressure decreases, water vaporizes at lower temperatures. In regions of high flow velocity, such as propeller tips, localized pressure drops cause the liquid to vaporize abruptly, forming microscopic vapor bubbles.

In the initial stage of the cavitation process, vaporization occurs in low-pressure regions, forming bubbles. Subsequently, as these bubbles are transported to regions of higher pressure, they collapse rapidly. Following collapse, microjets are generated. During this phase, liquid particles move at high velocities (>100 m/s) and impact the material surface. Ultimately, these microjets cause microcracks on metal surfaces and, over time, lead to corrosion. The process concludes with mechanical damage on the propeller surface.

^{Mechanics of cavitation bubbles respectively (}Dental Reviews⁾

In simulation environments, fluid dynamics are modeled using Computational Fluid Dynamics to identify pressure distributions and cavitation risk zones. Additionally, high-speed camera imaging captures bubble behavior at the millisecond level.

The regions most susceptible to severe cavitation are the tips of propeller blades and pump inlets. Simulated modeling combined with material strength tests has shown that aluminum alloys exhibit low cavitation resistance.

^{Cavitation coefficients at various regions of a pump impeller (}Dlamini, Hashe, Kunene⁾

Improving the aerodynamic profile of propeller blades and expanding flow channels to reduce pressure fluctuations can minimize cavitation risk. The use of cavitation-resistant materials such as titanium alloys or ceramic coatings, as well as the addition of anti-cavitation additives to the fluid, can delay the cavitation process. These methods extend material lifespan and provide economic and environmental benefits.