Where does cavitation erosion typically occur on a wet liner?

Cavitation erosion typically occurs on the wet liner in areas where the pressure fluctuates significantly, particularly where the fluid dynamics are most active. One of the primary locations for this phenomenon is aligned with the piston thrust faces. This area experiences high pressure and rapid motion as the piston moves during engine operation, leading to conditions that favor cavitation.

Cavitation takes place when there is a drop in pressure that allows vapor bubbles to form in the liquid. These bubbles can collapse violently when they move into areas of higher pressure, causing material erosion at the liner. The piston thrust faces represent a critical region where the hydraulic pressure can cause such fluctuations, making it a prime site for this type of erosion.

In contrast, other areas mentioned in the other choices may not experience the same high-velocity fluid flow or pressure variations that lead to cavitation erosion, which is why they would not be correct in this context.