Bragg Resonance of Water Waves and its Applications

Reza Alam, UC Berkeley
September 26th, 2012 at 4PM–5PM in 939 Evans Hall [Map]

Free propagating water waves traveling over bottom ripples may be significantly altered if certain conditions between wave characteristics and the topography are satisfied. This phenomenon is referred to as Bragg resonance, a name taken from the analogy to its close cousin in solid state physics of X-ray diffraction in periodic crystals. Bragg resonance of water waves contributes to the development of coastal wave spectrum, modifies bottom features, and may explain the generation of internal gravity waves in stratified fluids. I will present recent results on oblique and high-order nonlinear Bragg resonance of water waves in homogenous and stratified waters and discuss its effect on the ocean spectral evolution. These results may have a number of practical applications in the area of ocean engineering. Specifically I will briefly talk about how Bragg Resonance can help protecting offshore structures (such as offshore wind farms) against ocean waves, can transfer tidal current energy to the surface, and can focus ocean wave energy for high-efficiency wave energy absorption.