A new L type floating breakwater derived from vortex dissipation simulation. (15th September 2018)

• Record Type: Journal Article
• Authors: Zhang, Xiao-song; Ma, Shan; Duan, Wen-yang
• Is Part Of: Ocean engineering. Volume 164(2018)
• Page Start: 455
• Page End: 464
• Publication Date: 2018-09-15
• Subjects: Fixed floating breakwater -- Viscous dissipation -- Vorticity field -- L type floating breakwater -- Configuration improvement of FB; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2018.06.059
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: During the hydrodynamic analysis of the incident wave with the floating breakwater, the viscous effect for example the vortex generation and the energy dissipation is one of the issues, which affects the proper estimation of the wave protection performance. Traditional potential flow simulation is unable to solve the vortex dissipation. In this paper, the viscous flow simulation of wave-body interactions is carried out for a rectangular and inverted π type fixed floating breakwater (FB). The numerical accuracy of the viscous model is confirmed by comparison of the wave transmission and reflection coefficients between the viscous flow, potential flow, and experimental results. Furthermore, the vorticity field on these two types of FB are discussed and compared respectively, further, the characteristics like the vortex evolution, the flow pattern and the vorticity magnitude around the inverted π type fixed FB is analyzed in detail. Finally, an L type floating breakwater is designed and the sensitivity analysis of the principle dimensions on its wave protection property is performed. It has been demonstrated that L type floating breakwater has better comprehensive performance than rectangular and inverted π type floating breakwater under the same length of the protruding plate. Highlights: In the past, few study on the vortex phenomenon during the wave energy dissipation of floating breakwater and the relationship between the wave energy dissipation and the vortex has been made. In this paper, the hydrodynamic interaction between the incident waves and two types of fixed floating breakwaters are studied, including the inverted π type and the rectangular box type breakwaters. Through the comparative analysis of potential flow, viscous flow and experimental data, it is confirmed that the viscous effect due to the horizontal protruding plates has an influence on the wave energy dissipation performance of breakwaters. The detailed evolution of the vortex during one wave period is discussed and the effects of vortex on the periodical wave induced flow are analyzed. The horizontal protruding plates are proved to have a great effect on the vortex generation, which contributes to explain why the inverted π type breakwater has better performance than the rectangular box type breakwater. By comparing the vortex at the seaward side of the breakwater and that of the leeward side of the breakwater, it is found that the horizontal protruding plate on the seaward side of the breakwater plays a greater role in the dissipation of wave energy. Therefore, a breakwater structure with a horizontal protruding plate installed on the seaward side of the breakwater is proposed, which is named L type floating breakwater. By the calculation of transmission coefficient and reflection coefficient, This type of breakwater is proved to have better performance than the inverted π type breakwater.