Diffraction of water waves passing through a breakwater gap

Abstract

Efficient breakwater design requires a knowledge of the behavior of the waves passing the breakwater. Wave diffraction is an important factor in this behavior. Solutions based on the theory of light diffraction have been proposed for water‐wave diffraction, but have sot previously been experimentally verified for shallow water nor for waves entering breakwater gaps. This investigation found experimentally the wave patterns and comparative wave heights due to diffraction of water waves entering a gap in a breakwater normal to the incident wave direction in water of uniform depth, and compared these experimental results with approximate theoretical solutions. Both deep‐water and shallow‐water waves were studied. Oblique incidence and varying depths were not investigated experimentally, but approximate methods of considering their effect are suggested.The experimental results were found to verify the general form of the wave diffraction theory for breakwater gaps with gap width/wave‐length ratios as small as 1.41 in water of depth as small as 0.14 wave length.The theory and computation methods considered in this investigation form a usable basis for estimating the effect of diffraction on waves at a breakwater gap.