A Qualitative Description of Wave Breaking

Abstract

A description of major features and patterns of motion in water waves just after breaking is presented. Previous literature is synthesized and new observations utilized to develop a new qualitative picture of the breaking process. Both classic spilling and plunging‐type breakers are found to have similar initial breaking motions, but at vastly different scales. Two primary vortex motions are identified. A plunger vortex is initially created by the overturning jet, which in turn causes a splash‐up of trough fluid and subsequent formation of a surface vortex similar to the roller in a hydraulic jump. Introduced for the first time is the hypothesis that the plunger vortex translates laterally to push up a new surface wave with vastly different wave kinematics that continues propagating into the inner surf zone. Of primary interest is the outer or transition region where momentum is being exchanged between mean, periodic and random flow processes along with some energy loss. Evidence is presented from the literature to support the new, second wave hypothesis and all other concepts introduced.