ABSTRACT

Owing to its cutting-edge contour of the improved structure is not a straight line, a new comb-type floating breakwater is proposed in this paper. Experiments have been done in a wave flume to study the wave attenuation characteristics and the mooring forces of both the new comb-type and the rectangular box-type floating breakwaters under regular wave conditions. Results indicate that the transmission coefficient of the new comb-type FBW is eight percent lower than that of the rectangular box-type FBW. But the former can reduce the mooring force by twenty-five percent more than the latter. Through comprehensive consideration, the new comb-type can replace the rectangular box-type in engineering application. In addition, the effects of the relative width of the breakwater, the elasticity coefficient and incline angle of mooring lines on the hydrodynamic characteristics of the new comb-type FBW have also been studied.

INTRODUCTION

With the introduction of the concept of marine ranching, the scale of cage aquaculture has been expanding. Cage aquaculture has been pushed from the inner bay to the open sea. However, the severe sea conditions such as big waves and strong currents pose a serious threat to the safety of the cage system and restrict the rapid development of cage aquaculture. In order to ensure the safety of cages and avoid the losses caused by strong wind and big waves, it is an effective measure to arrange floating breakwater (FBW) around the cage for shield. FBWs can not only reduce waves, but also have the characteristics of low cost, convenient transportation, easy demolition, no damage to the ecological environment, and suitable for soft soil waters. At present, there are many types of FBWs, which rectangular box-type breakwater and based on the improvement of it have always been the focus of scholars at home and abroad. Songzhe Li (2016) studied the wave elimination performance of a new type pontoon FBW under the action of regular waves by wave flume cross-section test. Xiaonan Tang proposed a new type of box-type FBW to study wave dissipation characteristics and maximum mooring force under the action of regular waves and irregular waves. Zhixiong Ma et al. (1986) studied wave attenuation characteristics of the structure improved by pontoon and the mooring forces of FBW by model experiment. Guoquan Yao (1992) studied the rectangular FBW systematically. For different forms of rectangular box-type structure, the variation of the transmission coefficient first increases with the increase of the wave period and then decreases. The mooring force varies with the wave period, which is related to the structure form. Williams A. N. et al. (1996) built a physical model of FBW under the action of wave transmission properties of two-dimensional mathematical model, and the correctness of the model is verified by physical model test. Sannasiraj S. A. et al. (1997) calculated the hydrodynamic characteristics of a rectangular box-type FBW by numerical and model tests.

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