Cavitation Prevention with Roughened Surface

Experiments show that a rough surface reduces the pressure drop and likelihood of cavitation downstream of the roughness. A rough surface upstream of an irregularity significantly reduces the pressure drop caused by the irregularity. The effect of the rough surface is a function of the roughness d/s and can prevent cavitation damage. If an irregularity is inevitable, increasing the roughness of the upstream surface in front of the irregularity will reduce the possibility of cavitation caused by the irregularity. For the curved open channel used in this study of the flow in a spillway, the critical height of the irregularity was increased six to eight times at the downstream tangential point of the curve, and the negative pressure caused by the irregularity was reduced enough to prevent cavitation.