EXPERIMENTAL STUDY OF WAVE BREAKING CRITERIA AND ENERGY LOSS CAUSED BY A SUBMERGED POROUS BREAKWATER ON HORIZONTAL BOTTOM

Study on the criteria of wave breaking and energy loss caused by a submerged porous breakwater on a horizontal bottom has been performed experimentally in a 2-D wave tank. Wave conditions as well as the freeboard of the submerged breakwater, with the front slope of 1/2 and 1/5, are varying in the experiments. Results show that almost all tested waves can be triggered to break when the ratio of the estimated equivalent deepwater wave height to the freeboard of the submerged breakwater is greater than one. Results also reveal that a milder front slope of submerged breakwater may not trigger wave breaking more efficiently as that with a steeper front slope does. Furthermore, for a given freeboard of submerged breakwater, longer waves are more difficult to be triggered to break than shorter waves as expected. It is found that a submerged breakwater function much more efficiently if waves can be triggered to break by the structure as expected. Furthermore, it is also found that the submerged breakwater with milder front slope consumes more wave energy than that with steeper one through a wider range of porous structure.