Journal of Korean Society of Coastal and Ocean Engineers (한국해안해양공학회지)

Korean Society of Coastal and Ocean Engineers (한국해안·해양공학회)
권호 표지

Resonant Characteristics in Rectangular Harbor with Narrow Entrance (2.Effects of Entrance Energy Loss)

개구부가 좁은 직사각형 항만의 공진 특성 (2.항입구 에너지 손실의 영향)

  • 정원무 (한국해양연구소 연안·항만공학연구센터) ;
  • 박우선 (한국해양연구소 연안·항만공학연구센터) ;
  • 서경덕 (서울대학교 지구환경시스템공학부) ;
  • 채장원 (한국해양연구소 연안·항만공학연구센터)
  • Published : 1999.12.01
Download PDF
⟨ Previous Next ⟩

Abstract

A Galerkin finite element model for the analysis of harbor oscillation has been developed based on the extended mild-slope equation. Infinite elements are used to accomodate the radiation condition at infinity and joint elements to treat the matching conditions at the harbor entrance which include the energy loss due to flow separation. The numerical tests for rectangular harbors with fully or partially open entrances show that the energy loss at the harbor entrance considerably reduces the the amplification ratios at the innermost parts of the harbors and that the amplification ratios decrease considerably with increasing incident wave heights and jet lengths at the harbor entrance. Application of the model to the Gamcheon harbor show that when the incident wave amplitude is small the amplification ratios rather increase when the entrance energy loss is included than when ignored because of the shift of the resonance periods. Even though the entrance energy loss was insignificant for the measured long-period incident waves, it would be of great importance if the incident waves were large as in the attack of tsunamis. The resonance period of the Helmholtz mode at the Gamcheon Harbor was calculated to be 31 minutes, which agrees well with the measured one between 27 and 33.3 minutes. The measured resonance periods between 9.4 and 12.1 minutes and 5.2 and 6.2 minutes were also calculated by the numerical model as 10.4 minutes and 6.6 or 5.6 minutes, indicating good performance of the model. On the other hand, it was shown that a variety of oscillation modes exists in the Gamcheon Harbor and lateral resonances of considerable amplification ratios also exist at the periods of 3.6 and 1.6 minutes as in the Young-II Bay.

확장형 완경사방정식을 지배방정식으로 사용하며 무한원방에서의 방사조건은 무한요소로, 그리고 항입구에서의 흐름분리로 인한 에너지 손실의 고려는 정합요소로 처리하는 Galerkin 유한요소 모형을 개발하였다. 완전 및 부분 개방 직사각형 항만에 대한 수치실험 결과 항입구에서의 에너지 손실의 포함은 港奧에서의 증폭비를 상당히 감소시키는 것으로 나타났으며, 입사파고와 제트 길이의 증가는 증폭비의 상당한 감소를 초래하였다. 감천항에서 제트길이를 고려한 경우 공진주기의 이동으로 입사파 진폭이 작을 때는 손실을 고려하지 않은 경우보다 진폭비가 오히려 크게 나타났다. 관측된 입사 장주기 파고의 사용시에는 항입구 손실이 작은 것으로 나타났으나 지진해일의 내습시와 같이 파고가 큰 경우에는 상당한 입구 손실이 예상되었다. 감천항의 Helmholtz 공진모드는 주기 31.0분으로 제시되어 관측 겨로가인 27.0~33.3분과 잘 일치하였다. 또한 관측치인 주기 9.4~12.1분과 5.2~6.2분의 공진모드도 10.4분과 6.6분 또는 5.6분으로 상당히 재현되었다. 한편, 감천항에는 매우 다양한 모드의 부진동이 존재하는 것으로 나타났으며, 영일만 마찬가지로 주기 3.6분과 1.6분에서 상당한 진폭비의 횡방향 공진이 존재함을 확인하였다.

Keywords

References

  1. 해양연구 v.11 no.2 영일만과 포항신항의 부진동 현상 강석구;이상룡;소재귀
  2. 한국해안 · 해양공학회지 v.6 no.4 Galerkin 유한요소법에 의한 항내 정온도 모형 서승남;연영진
  3. 서울대학교 박사학위논문 항만부진동에 대한 현장연구와 유한요소 해석 정원무
  4. 한국해안 · 해양공학회지 v.8 no.2 항만 공진에 대한 복합요소 수치모형 민감도 분석 정원무;박우선
  5. 해양연구 v.20 no.2 항입구 손실과 저면마찰을 고려한 항만부진동 유한요소 모형 정원무;이길성;박우선;정경태
  6. 한국해안 · 해양공학회지 v.7 no.1 묵호항의 항내 진동 정원무;정경태;채장원
  7. 구속파의 전파 특성 해석 정원무;채장원;전기천;이종찬;조홍연;김용권;백원대;박승준;김미경
  8. Proc. 13th Coastal Engrg. Conf. Computation of combined refraction-diffraction Berkhoff, J.C.W.
  9. J. Fluid Mech. v.79 Harbour resonance due to set-down beneath wave groups Bowers, E.C.
  10. J. Fluid Mech. v.291 The modified mildslope equation Chamberlain, P.G.;Porter, D.
  11. Applied Ocean Res. v.8 no.2 Effects of bottom friction and boundary absorption on wave scattering Chen, H.S.
  12. J. Korean Soc. Coastal and Ocean Engrs. v.9 no.2 Control of seiches by adjustment of entrance channel width Cho, Y.J.
  13. Coastal Engrg. v.11 Modelling dissipation in harbour resonance Gerber, M.
  14. Coastal Engrg. in Japan v.13 Onthe effect of tsunami breakwater Ito, Y.
  15. Proc. 25th Coastal Engrg. Conf. Field measurements and numerical modeling of harbor oscillations during storm waves Jeong, W.M.;Chae, J.W.;Park, W.S.;Jung, K.T.
  16. Report KH-R-20 Wave induced oscillations in harbors of arbitrary shape Lee, J.J.
  17. J. Fluid Mech. v.45 Wave-induced oscillation in harbors of arbitrary shape Lee, J.J.
  18. Report No. KH-R-41 Tsunamis- harbor oscillations induced by nonlinear transient long waves Lepelletier, T.G.
  19. Coastal Engrg. v.19 Extended refraction-diffraction equation for surface waves Massel, S.R.
  20. The Applied Dynamics of Ocean Surface Waves Mei, C.C.
  21. Proc. Symp. on Medeling Techniques Hybrid-element method for water wave Mei, C.C.;Chen, H.S.
  22. J. Fluid Mech. v.46 Resonant response of harbours: An equivalent-circuit analysis Miles, J.W.
  23. J. Fluid Mech. v.67 Helmholtz resonance of harbors Miles, J.W.;Lee. Y.K.
  24. J. Waterways and Harbors Div. v.87 no.WW3 Harbor paradox Miles, J.W.;Munk, W.
  25. Methods of Theoretical Physics Morse, P.M.;Feshbach, H.
  26. Theoretical Acoustics Morse, P.M.;Ingard, K.U.
  27. Coastal Engrg. in Japan v.19 A solution for wave-induced oscillations in harbors considering energy dissipation Murakami, H.
  28. J. Korean Soc. Coastal and Ocean Engrs. v.6 no.2 Infinite element for the analysis of harbor resonances Park, W.S.;Chun, I.S.;Jeong, W.M.
  29. Proc. Int. Symp.: Waves -Physical and Numerical Modelling The effects of disspation on experimental and numerical models of harbor resonance Raichlen, F.;Lee, J.J.;Lepelletier, T.G.
  30. Math. Ann. v.47 Mathematische theorie der diffraction Sommerfeld, A.
  31. Coastal Engrg. v.32 Time-dependent equations for wave propagation on rapidly varying topography Suh, K.D.;Lee. C.;Park, W. S.
  32. J. Waterways, Harbours and Coastal Engrg. Div. v.101 no.WW2 Effects of entrance loss on harbor oscillations Unluata, U.;Mei, C C.
  33. J. Waterways, Habors and Coastal Engrg. Div. v.88 no.WW2 Disscussion of "Harbor paradox" Wilson, B.W.;Miles, J.W.(ed.);Munk, W.J.(ed.)