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Hydrodynamic Analysis of Two-dimensional Floating Breakwater in Weakly Nonlinear Waves

약 비선형 파랑에 대한 연직 2차원 부방파제의 동수역학적 해석

  • 이정우 (한국건설기술연구원 수자원연구부) ;
  • 조원철 (연세대학교 사회환경시스템공학부 토목환경전공)
  • Received : 2005.12.19
  • Accepted : 2006.08.21
  • Published : 2006.09.30

Abstract

The performance of a pontoon-type floating breakwater (FB) is investigated numerically with the use of a second-order time domain model. The model has been developed based on potential theory, perturbation theory and boundary element method. This study is focused on the effects of weakly nonlinear wave on the hydrodynamic characteristics of the FB. Hydrodynamic forces, motion responses, surface elevation, and wave transmission coefficient around the floating breakwater are evaluated for various wave and geometric parameters. It is shown that the second-order wave component is of significant importance in calculating magnitudes of the hydrodynamic forces, mooring forces and the maximum response of a structure. The weak non-linearity of incident waves, however, can have little influence on the efficiency of the FB. From numerical simulations, the ratio of draft and depth, the relationship of wave number and width are presented for providing an effective means of reducing wave energy.

본 연구에서는 포텐셜 이론, 섭동법, 경계요소법에 근간을 둔 이차의 시간영역 수치모델을 개발하고 이를 이용하여 폰툰형 부방파제의 성능을 평가하였다. 다양한 설계조건에 대하여 파력, 운동변위, 자유수면고, 투과율 등의 변화를 고찰하였으며, 파랑의 약 비선형성이 방파제의 동수역학적 특성에 미치는 영향을 분석하는데 주안점을 두었다. 수치모의 수행 결과, 이차의 성분 파는 동유체력, 계류장력, 운동변위에 미치는 영향이 큰 것으로 분석되었으나, 파랑의 약 비선형성이 투과율에 미치는 영향은 매우 작아 선형해석만으로도 파랑제어효율을 평가할 수 있음을 확인하였다. 또한 파랑제어효율이 우수한 수심과 흘수의 비, 파수와 폭과의 관계 등을 제시하였다.

Keywords

References

  1. 김도삼, 이광호, 최낙훈, 윤희면 (2004) 신형식 부방파제의 파랑제어에 관한 연구, 한국해안해양공학회지, 한국해안.해양공학회, 제16권 제1호, pp. 1-9
  2. 김도삼, 기성태, 허동수, 박경수, 이상기 (2005a) 복합판형 부소파제에 의한 파랑제어기능과 동적거동에 관한 연구, 대한토목학회 정기학술대회, pp. 796-799
  3. 김도삼, 박경수, 김창훈, 오윤석 (2005b) 연직판각형 부소파제에 의한 파랑제어기능과 동적거동에 관한 연구, 대한토목학회 정기학술대회, pp. 1967-1970
  4. 양우석, 조원철, 박우선 (2001) 부유식 방파제의 파랑 차단 성능 제어, 한국해안해양공학회지, 한국해안.해앙공학회, 제13권 제3호, pp. 230-236
  5. 전인식 (1993) 케티너리 계류 부유식 방파제 거동의 시간영역 해석, 한국해안해양공학회지, 한국해안.해양공학회, 제5권 제3호, pp. 182-190
  6. 정신택, 박우선, 이호찬 (2002) 다열 부유식 방파제의 유한요소 해석, 한국해안해양공학회지, 한국해안.해양공학회, 제14권 제4호, pp. 257-264
  7. Adee, B.H. and Martin,W. (1974) Analysis of floating breakwater performance, Proceedings of the Floating Breakwater Conference, University of Rhode Island. RI. pp. 21-40
  8. Buchmann, B., Skoourup, J., and Cheung, K.F. (1998) Run-up on a structure due to second-order waves and a current in a numerical wave tank, Applied Ocean Research, Vol. 20, pp. 297-308 https://doi.org/10.1016/S0141-1187(98)00022-4
  9. Cointe, R, Geyer, P., King, B., Molin, B., and Tramoni, M. (1990) Nonlinear and linear motions of a rectangular barge in a perfect fluid, Proc. 18th Symp. On Naval Hydrodynamics, pp. 85-99
  10. Contento, G. (1996) Nonlinear phenomena in the motions of unrestrained bodied in a numerical wave tank, Proc. 6th Int. Offshore and Polar Eng. Conf, ISOPE, Los Angeles, CA, Vol. 3, pp.18-22
  11. Grue, J. and Palm, E. (1993) The mean drift force and yaw moment on marine structures in waves and current, Journal of Fluid Mechanics, Vol. 250, pp. 121-142 https://doi.org/10.1017/S0022112093001405
  12. Isaacson, M. and Cheung, K.F. (1991) Second-order wave diffraction around two-dimensional bodies by time-domain method, Applied Ocean Research, Vol. 13, No. 4, pp. 175-186 https://doi.org/10.1016/S0141-1187(05)80073-2
  13. Isaacson, M. and Ng, J.Y.T. (1993) Time-domain second-order wave radiation in two dimensions, Journal of Ship Research, Vol. 37, No. 1, pp. 25-33
  14. Jeongwoo Lee, Woncheol Cho (2003) Hydrodynamic analysis of wave interactions with a moored floating breakwater using the element free Galerkin Method, Canadian Journal of Civil Engineering, Vol. 30, No. 4, pp. 720-733 https://doi.org/10.1139/l03-020
  15. Kim, M.H. and Yue, D.K.P. (1990) The complete second-order diffraction solution for an axisymmetric body. Part 2. Bichro-matic incident waves and body motions, Journal of Fluid Mechanics, Vol. 211, pp. 557-593 https://doi.org/10.1017/S0022112090001690
  16. Kim, M.H. and Yue, D.K.P. (1991) Sum-and difference frequency wave loads on a body in unidirectional Gaussian seas, Journal of Ship Research, Vol. 35, No. 2, pp. 127-140
  17. Koo, W.C, and Kim, M.H. (2004) Freely nonlinear wave-body simulation by a 2D fully nonlinear numerical wave tank, Ocean Engineering, Vol. 31, pp. 2011-2046 https://doi.org/10.1016/j.oceaneng.2004.05.003
  18. Leonard, J.W., Huang, M.-C. and Hudspeth, R.T. (1983) Hydrody-namic interference between floating cylinders in oblique seas, Applied Ocean Research, Vol. 5, No. 3, pp. 158-166 https://doi.org/10.1016/0141-1187(83)90071-8
  19. Liu, Y, Yue, D.K.P., Kim, M.H. (1993) First- and second-order responses of a floating toroidal structure in long-crested irregular seas, Applied Ocean Research, Vol. 15, No 3, pp. 155-167 https://doi.org/10.1016/0141-1187(93)90038-Y
  20. Malenica, S. and Molin, B. (1995) Third-harmonic wave diffraction by a vertical cylinder, Journal of Fluid Mechanics, 302, pp. 203-229 https://doi.org/10.1017/S0022112095004071
  21. Ng, J.Y.T and Isaacson, M. (1992) Second-order wave interaction with two-dimensional floating bodies by a time-domain method, Applied Ocean Research, Vol. 15, pp. 95-105 https://doi.org/10.1016/0141-1187(93)90024-R
  22. Pierson, W.J. (1993) Oscillatory third-order perturbation solutions for sums of interacting long-crested Stokes waves on deep water, Journal of ship research, Vol. 37, No. 4, pp. 354-
  23. Sannasiraj, S.A., Sundar, V, and Sundaravadivelu, R. (1998) Mooring forces and motion responses of pontoon-type floating breakwaters, Ocean Engineering, Vol. 25, No. 1, pp. 27-48 https://doi.org/10.1016/S0029-8018(96)00044-3
  24. Sclavounos, P.D. and Kim, Y.W. (1995) Third order diffraction of surface waves by a time-domain ranking panel method, Proceedings of the 10th International Workshop on Water Waves and Floating Bodies, Oxford. UK
  25. Zhao, R. and Faltinsen, O.M. (1989) Interaction between current waves and marine structures, Proceedings of the 5th International Conference on Num. Hydrodynamics, Hiroshima, Japan, National Academy Press, Washington