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Numerical simulations on waves of perforated breakwater with two chambers
|引用:||1.蔡清標、王柏棟、林建志、王志成、陳吉紀(2011) “梯形消波艙防波堤之波流場解析”，海洋工程學刊第11卷第1期，57頁-70頁 2.Bergmann, H., Oumeraci, H. (2000) “Performance of new multi chamber system vs conventional Jarlan caisson breakwaters,” Journees Nationales Genie Civil- Genie Cotier, Caen, France, pp. 17-19 Mai 2000 3.Fugazza, M. and Natale, L. (1992) “Hydraulic design of perforated breakwaters,” Journal of Waterway, Port, Coastal, and Ocean Engineering, ASCE, Vol. 118, No. 1, pp. 1–14. 4.Goda, Y. and Suzuki, Y. (1976) “Estimation of incident and reflected waves in random wave experiments,” Proceedings of the 15th Conference on Coastal Engineering, ASCE, pp. 828 – 845. 5.Goda, Y. (1985) “Random Seas and Design of Maritime Structures,” University of Tokyo Press, Tokyo, Japan. 6.Hirt, C.W., Nichols, B.D., (1981.) “Volume of fluid method for the dynamics of free boundaries,” Journal of Computational Physics 39, pp. 201– 225. 7.Hirt, C.W., Sicilian, J.M., (1984) “An efficient computation scheme for tracking contaminant concentrations in fluid flows,” Journal of Computational Physics, Vol. 56, pp. 428-447. 8.Jarlan, G.E. (1961) “A perforated vertical wall breakwater,” Dock & Harbour Authority 41 (486), pp. 394–398. 9.Kondo, H.,(1979) “Analysis of breakwaters having two porous walls,” Coastal Structures ''79, Alexandria, Virginia, pp. 962–977. 10.Lemos, C.M., (1992) “A simple numerical technique for turbulent flow with free surface,” International Journal for Numerical Methods in Fluids 15, pp. 127– 146. 11.Li, Y.C., Dong, G.H., Liu, H.J., Sun, D.P., (2003) “The reflection of oblique incident waves by breakwaters with double-layered perforated wall,” Coastal Engineering 50, pp. 47–60. 12.Liu, Y., Li, Y., Teng, B., Jiang, J., Ma, B. (2008) “Total horizontal and vertical forces of irregular waves on partially perforated caisson breakwaters,” Coastal Engineering, Vol. 55, pp. 537–552 13.Mansard, E.P.D., Funke, E.R., (1980) “The measurement of incident and reflected spectra using a least squares method,” Proc. 17th Costal Engineering Conference, ASCE, pp. 154 – 172. 14.Marks, W. and Jarlan G. E. (1968) “Experimental studies on a fixed perforated breakwater,” Proc. of 11th Conf. on Coastal Engineering 15.Oumeraci, H (2010) “Nonconventional wave damping structures,” In Handbook of Coastal and Ocean Engineering, World Scientific, pp. 287-315. 16.Sekiguchi, S.I., Miyabe, S., Yamamoto, Y., Miwa, T., (2002) “Development of a sloping-slit caisson breakwater,” Coastal Engineering Journal, Vol. 44, No. 3, pp. 203 - 215. 17.Suh, K.D., Park, W.S., (1995) “Wave reflection from perforated-wall caisson breakwaters,” Coastal Engineering, Vol. 26, pp. 177–193. 18.Suh, K.D., Park, W.S., Park, J.K. (2006) “Wave reflection from partially perforated-wallcaisson breakwater,” Proc. Ocean Engineering, Vol. 33, pp. 264–280. 19.Suh, K. D. (2010) “Wave interaction with breakwaters including perforated walls,” In Handbook of Coastal and Ocean Engineering, World Scientific, pp. 317-339. 20.Takahashi, S. (1999) “Failure of composite breakwaters in Japan,” Proc. Lect. Port Harbar Res Inst. 21.Williams, A.N., Mansour, A.E.M., Lee, H.S., (2000) “Simplified analytical solutions for wave interaction with absorbing-type caisson breakwaters,” Ocean Engineering 27, pp. 1231–1248.|
|摘要:||It is well known that a perforated-wall caisson breakwater reduces not only the wave reflection but also the wave forces. In this paper, the numerical simulation was presented to investigate the characteristics of waves on the caisson breakwater with trapezoidal wave-chambers which consists of two layers of slit wall. The three-dimensional RANS with RNG turbulent model was applied for the numerical simulation that was implemented with a CFD code, FLOW-3D.
The numerical results of wave profiles and pressure variations were first verified with the experimental data. The results of reflection coefficient with varied width of wave-chamber was compared with the previous experimental results as well. The wave reflection, the wave force, the turbulent energy dissipation and the different porosities of perforated wall were analyzed. As the wave passes through the perforated wall, the particle velocity increased and the vortex formed. When the wave passes the upper sloping-slit, the downward flow is generated. Turbulent dissipation usually occurs near the perforated wall which induces a greater energy loss it. The numerical simulations show the obvious reduction of the wave reflection and the wave force by the wave-chambers. The results indicated that the wave reflection from the wave-chamber and the wave force on the breakwater is minimal when B/L is about 0.15 where L is the wavelength and B is the width of wave chamber. Even for B/L = 0.2-0.5, the wave reflection and the wave force may be reduced in a great extent.|
根據以往對於開孔防波堤之研究，其具消波艙室開孔防波堤確實能有效降低反射率及波壓力。本研究針對具梯形消波艙室防波堤探討，在消波艙室內增設一層開孔牆形成雙消波艙室並進行波流場解析，文中並探討波浪反射率、堤面波壓力分佈及紊流能損等特性，數值解析系以三維RANS方程式結合RNG紊流模式為基礎，以有限差分法配合FAVOR網格障礙物處理技術及流體體積法解析防波堤與波浪的交互作用。 經由Flow-3D計算流體力學軟體模擬與模型試驗之波形與波壓分布及前人研究之防波堤反射率相互驗證，顯示計算結果具有很好的精確度。本文中探討具雙層消波艙室防波堤之相對寬度(B/L)與反射率及波力關係，以及不同開孔佈置之影響，並觀察波流場及紊流消散情形。波浪經開孔牆時因通水面積減小流速變大集中流出，而斜面開孔也使波浪入射後產生向下跌落之水流，造成流場紊亂且有渦流產生，能損主要產生於開孔附近，且當水流進出開孔牆時能損較大。根據模擬之結果，具雙層消波艙室開孔防波堤之反射率及波力有明顯的消減，且研究結果顯示B/L=0.15時，其在降低反射率及波力效果最佳，其波浪反射率約為0.2，波力比約為0.375，並在B/L=0.2 ~ 0.5間都能有效降低反射率及波力。前堤面與中間隔層之開孔是否交錯佈置並不影響反射率，而在固定前堤面開孔率λ1=0.25條件下，中間隔層開孔率λ2 減半，能在相對寬度B/L≧0.3範圍有更好之消波效能。
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