Lateral Instability of Overtopping Jets Evolving into Fingering Surfaces

Abstract

Lateral instability of overtopping jets is manifested when a breaking wave hits a vertical wall, resulting in formation of so-called finger jets. This study presents that the instability is caused by changes in orientation of capillary waves on the stretched surface rising at high acceleration, and that the evolution of the resulting fingers depends on relative distance between the breaking point and location of the wall. Population of the sprays with very high rise velocity over 9 m/s significantly increases when incident waves break in front of the wall due to expansion of air pocket squeezed between the jet and wall.