WAVES

Among the diverse wave motions, edge waves are a kind of wave which is trapped near shore and travels alongshore. Edge waves are of significance in both nearshore hydrodynamics and morphodynamics. Much research has been conducted on the excitation mechanism of standing edge waves on sloping beaches and their morphodynamic implications. It has been widely accepted that "standing" edge waves can be excited near the shoreline and one theory suggests that they can lead to cusp formation. However, comprehensive direct field observations of standing edge waves on natural beaches have not yet been found and previous studies were mostly conducted by assuming monochromatic incoming waves. The excitation of edge wave with coastal random waves remains unclear. 

We conducted large scale laboratory experiments to explore the subharmonic edge wave excitation. Results with monochromatic incoming waves confirm previous research. A new phenomenon, intermittent edge wave excitation, was observed with random incoming waves. Subharmonic edge wave amplitudes sometimes varied temporally, over many wave periods, between essentially zero (no edge waves) and the relatively large amplitudes seen with monochromatic incident waves. More research are undergoing to explore the mechanism behind this new phenomenon.

Contact: Xuelin Ding at  xdin286@aucklanduni.ac.nz