Abstract
Ships take in seawater as weight to keep its balance. This is called ballast water. Ballast water contains various microbe (planktons, fish eggs and bacteria, etc) in the sea. So discharge of ballast water gives bad influence on ecosystem of other sea area. This paper presents effect of destruction of planktons when cavitating jet impinges on target body. We researched what kind of target body and distance is more effective on destructing planktons. Target body shapes flat, U-notch, V-notch and horn-shaped target. Distance between nozzle and target body is 2mm, 4mm, 6mm, 8mm and 12mm. The experimental result showed that the horn-shaped target and the distance 8mm between nozzle and target body was most effective in destructing planktons. It was caused by the collapse of cavitation bubbles at the horn and shearing stress at the shoulder of target body.
