On the use of the method of images to investigate nearshore dynamical processes

This note describes how the method of images may be used to determine the m otion and evolution of two related kinds of phenomena within a wedge of inv iscid fluid. The image field of a curved vortex within a wedge with vortex lines lying along sectors of circles around the apex of the wedge is that s egment of a complete vortex ring which remains outside the wedge and of whi ch the curved vortex forms a part. The image system can be used to describe the motion, interaction and stability of single or multiple vortices withi n the wedge. Axisymmetric jets form the image system for flow parallel to t he edge of the wedge, akin to alongshore currents. Knowledge of the instabi lity of jets provides information about the evolution of waves in the wedge domain. Existing results on the motion and instability of single or multip le co-axial ring vortices and of waves and instabilities in jets may be app lied to describe the evolution of low Froude number eddies and waves in alo ngshore flow over a steadily shelving sea bed.