Experimental study on the hydrodynamic performance of a side-by-side box-membrane breakwater

In this paper, the hydrodynamic performance of a proposed side -by -side box-membrane breakwater is experimentally studied in regular waves. The proposed breakwater consists of two identical breakwaters placed away from each other with an empty gap e , and each component breakwater is a combination of a rectangle rigid box and double layered flexible membranes which hanged freely below the box. For comparison, a side -by -side breakwater consisted of two boxes without flexible membrane is chosen, as well as e = 0. A series of preliminary experiments are carried out in a 2D wave flume, and the hydrodynamic performance under different parameters, including relative width 2 B/ lambda (box width B , wave length lambda ), length of flexible membrane, gap e between the two boxes, and box draft d are investigated. The results indicate that, both the narrow and wide gaps of the side -by -side box-membrane breakwater can achieve a well wave attenuation performance in relatively long waves. Specifically, the proposed side -by -side breakwater with the wide gap could reach a transmission coefficient less than 0.5 at B/ lambda = 0.0633 when the Bragg reflection occurs at about 2 S/ lambda = 1.0 ( S = e + B ). It is also found that attaching flexible membrane and increasing box draft could enhance the wave attenuation performance, which concur with those seen in other studies.