Study On The Hydrodynamic Performance Of A Submerged Perforated Wall Breakwater

Breakwaters are used to protect coastlines, coastal structure and harbor basin.Traditional breakwaters are surface-piercing and then affect to the coastal landscape.Submerged breakwaters can reflect and dissipate the energy of incident waves andthen reduce the damage of structures and shorelines without affecting the coastallandscape. Now breakwaters are making toward developed as permeable breakwatersand multi-functional breakwaters, such as horizontal plate breakwaters, perforatedcaissons and semi-circular perforated breakwaters. On the basis of traditionalperforated caissons, we present a new submerged perforated wall breakwater withbetter wave-absorbing performance.This work studies the hydrodynamic performance of submerged perforated wallbreakwater by physical model test and theoretical analysis. The reflectioncoefficient, transmission coefficient and wave forces acting on the breakwater areexamined.Experimental tests were conducted in a wave-current flume of Shandong ProvincialKey Laboratory of Ocean Engineering. The effects of relative chamber width B/L,relative water depth d/L, porosity of front plate and relative wave height H/d on thereflection and transmission coefficients are examined based on the experimental data.An analytical solution of wave interaction with the perforated wall breakwater isdeveloped based on the matched eigenfunction expansions. The reflection andtransmission coefficients and wave forces are examined. The analytical results for thereflection and transmission coefficients are the same as previous analytical andnumerical results and agree well with experimental data. The optimum parameters forthe submerged perforated wall breakwater are: d/h=0.1–0.2, B/L=0.3–0.4, ε=0.1–0.2. At this time, the breakwater has better wave absorbing performance withlow reflection and transmission coefficients and low wave force. Efficient shelter canbe provided for leeside regions and the scour in front of the structure is suppressed. These are of significant in practice.