Wave reflection and transmission test with pipe wall roughness and without roughness on the perforated breakwater

Abstract

Waves towards the shore that have a porous breakwater building will experience reflection and transmission, to determine the height of reflection and transmission wave is needed a study by the process of generating waves on the flume with a porous breakwater building, the effect of wave changes in its propagation requires an experiment in the laboratory. This study was aimed to determine the height ratio of reflection and transmission wave by using a model of pipe structure as a wave reducer by adding the friction plane of the roughness of the walls in the pipe. A method of laboratory experiment on the wave generation flume has several variations consisting of 3 periods (T; 1,0 seconds, T; 1,1 seconds, T; 1.2 seconds) and 3 water depth (d) are 15, 30 and 36 cm, stroke to regulate the flap motion that determines the wave height (H) as a wave generator that is 4, 5 and 6 by comparing the model that uses pipe wall roughness and without roughness. The result of testing indicates that the height of reflection wave (Hr) and transmission (Ht) is strongly influenced by the period (T). If the period increases, Hr and Ht significantly decrease, the height ratio of reflection wave using pipe wall roughness is greater than without roughness. However, it inversely proportional to the height of transmission wave (Ht) were a model using pipe roughness is more efficient to reduce Ht than a model without pipe roughness.