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Keywords: submerged permeable breakwater, shoreline change, time-dependent mild-slope equation, continuity equation of sediment.

Summary

When waves pass a submerged permeable breakwater, the wave heights may decay over the breakwater as a result of wave energy dissipation and the induced circulation current system behind the structure is likely to make the sand deposit. On the other hand, the porous breakwater has the function of ecological restoration and has less impact on the coastal environment. Thus it is used increasingly by costal engineers for prevention of coastal erosion. Significant literature has paid attention to the wave transformation passing the submerged breakwater. In this paper, a numerical model is presented for simulating the shoreline change in the lee of a permeable submerged breakwater.

In the past, many numerical models were proposed to simulate the shoreline changes. These models include two-dimensional line models [1,2,3,4] for the long-term shoreline change or a three-dimensional model [5] for the short-term topography variation. However, previous models considered the coastal structure as an impermeable one, rather than the porous structure considered in this paper.

In the present model, the wave field around the submerged permeable breakwater was first calculated based on the time-dependent mild slope equation proposed by Tsai et al. [6] that the porous parameters of the structure were involved. Then, the long-term shoreline change model is then established based on the continuity equation of the sediment, in which the longshore sediment transportation due to the effect of the wave diffraction is calculated using the breaking wave energy flux.

The movable-bed experiments were also conducted in a two-dimensional wave basin for verifying the simulated results. The comparisons show that the numerical results of the wave height variations and the shoreline change are well in agreement with the experimental results.

References

1: R. Pelnard-Considere, "Essai de theorie de l'evolution des forms de vivage en plages de sable et de dalets", IVeme Journees de l'Hydraulique, Les Energies de la Mer, Question III, Report, No. 1, 289-298, 1956.
2: W.T. Bakker, "The dynamic of a coast with a groin system", Proceedings of 11th Conference On Coastal Engineering, ASCE, 492-517, 1978.
3: D.H. Willis, "Sediment load under waves and current", Proceedings of 16th Conference on Coastal Engineering, ASCE, 1626-1637, 1980.
4: M. Perlin, R.G. Dean, "A numerical model to simulate sediment transport in vicinity of coastal structures", Miscellaneous Report 83-10, Coastal Engineering Research Center, U.S. Army Corps of Engineers, VA, 1978.
5: A. Watanabe, K. Maruyama, "Numerical modeling of nearshore wave field under combined refraction, diffraction and breaking", Coastal Engineering in Japan, 29, 19-39,1986.
6: C.P. Tsai, H.B. Chen, F.C. Lee, "Wave transformation over submerged permeable breakwater on porous bottom", Ocean Engineering, 33, 1623-1643, 2006. doi:10.1016/j.oceaneng.2005.09.006

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 94 PROCEEDINGS OF THE SEVENTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: Paper 82 Simulation of the Shoreline Change behind a Submerged Permeable Breakwater C.P. Tsai¹, C.W. Hung¹ and H.B. Chen² ¹Department of Civil Engineering, National Chung Hsing University, Taichung, Taiwan ²Department of Sports, Health, and Leisure, Chihlee Institute of Technology, Taipei, Taiwan doi:10.4203/ccp.94.82 purchase the full-text of this paper Full Bibliographic Reference for this paper C.P. Tsai, C.W. Hung, H.B. Chen, "Simulation of the Shoreline Change behind a Submerged Permeable Breakwater", in , (Editors), "Proceedings of the Seventh International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 82, 2010. doi:10.4203/ccp.94.82 Keywords: submerged permeable breakwater, shoreline change, time-dependent mild-slope equation, continuity equation of sediment. Summary When waves pass a submerged permeable breakwater, the wave heights may decay over the breakwater as a result of wave energy dissipation and the induced circulation current system behind the structure is likely to make the sand deposit. On the other hand, the porous breakwater has the function of ecological restoration and has less impact on the coastal environment. Thus it is used increasingly by costal engineers for prevention of coastal erosion. Significant literature has paid attention to the wave transformation passing the submerged breakwater. In this paper, a numerical model is presented for simulating the shoreline change in the lee of a permeable submerged breakwater. In the past, many numerical models were proposed to simulate the shoreline changes. These models include two-dimensional line models [1,2,3,4] for the long-term shoreline change or a three-dimensional model [5] for the short-term topography variation. However, previous models considered the coastal structure as an impermeable one, rather than the porous structure considered in this paper. In the present model, the wave field around the submerged permeable breakwater was first calculated based on the time-dependent mild slope equation proposed by Tsai et al. [6] that the porous parameters of the structure were involved. Then, the long-term shoreline change model is then established based on the continuity equation of the sediment, in which the longshore sediment transportation due to the effect of the wave diffraction is calculated using the breaking wave energy flux. The movable-bed experiments were also conducted in a two-dimensional wave basin for verifying the simulated results. The comparisons show that the numerical results of the wave height variations and the shoreline change are well in agreement with the experimental results. References 1 R. Pelnard-Considere, "Essai de theorie de l'evolution des forms de vivage en plages de sable et de dalets", IVeme Journees de l'Hydraulique, Les Energies de la Mer, Question III, Report, No. 1, 289-298, 1956. 2 W.T. Bakker, "The dynamic of a coast with a groin system", Proceedings of 11th Conference On Coastal Engineering, ASCE, 492-517, 1978. 3 D.H. Willis, "Sediment load under waves and current", Proceedings of 16th Conference on Coastal Engineering, ASCE, 1626-1637, 1980. 4 M. Perlin, R.G. Dean, "A numerical model to simulate sediment transport in vicinity of coastal structures", Miscellaneous Report 83-10, Coastal Engineering Research Center, U.S. Army Corps of Engineers, VA, 1978. 5 A. Watanabe, K. Maruyama, "Numerical modeling of nearshore wave field under combined refraction, diffraction and breaking", Coastal Engineering in Japan, 29, 19-39,1986. 6 C.P. Tsai, H.B. Chen, F.C. Lee, "Wave transformation over submerged permeable breakwater on porous bottom", Ocean Engineering, 33, 1623-1643, 2006. doi:10.1016/j.oceaneng.2005.09.006 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £125 +P&P)
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