In this paper the wave action balance equation in terms of frequency-direction spectrum is derived. A theoretical formulation is presented to generate an invariant frequency space to replace the varying wavenumber spa...In this paper the wave action balance equation in terms of frequency-direction spectrum is derived. A theoretical formulation is presented to generate an invariant frequency space to replace the varying wavenumber space through a Jacobian transformation in the wave action balance equation. The physical properties of the Jacobian incorporating the effects of water depths are discussed. The results provide a theoretical basis of wave action balance equations and ensure that the wave balance equations used in the SWAN or other numerical models are correct. It should be noted that the Jacobian is omitted in the wave action balance equations which are identical to a conventional action balance equation.展开更多
Two different methods for incorporating diffraction effect into wave action balance equation based coastal spectral wave models, WABED and SWAN, are discussed and evaluated with respect to their formulations, numerica...Two different methods for incorporating diffraction effect into wave action balance equation based coastal spectral wave models, WABED and SWAN, are discussed and evaluated with respect to their formulations, numerical implementations, and modeling capabilities. Both models were nm to simulate the wave transformation through a gap between two infinitely long breakwaters and that across an elliptical shoal observed in laboratory studies, with the emphasis laid on the diffraction induced by either obstacles or wave amplitude variations. Calculations of WABED were compared with Sommerfeld＇s analytical solutions, experimental observations and SWAN simulations. It is shown that both methods can predict reasonably wave diffraction for the two eases studied herein, and a fairly better performance is provided by WABED for stronger diffraction ease.展开更多
Recent research on short-term topographic change in the Yangtze Estuary channel under storm surge conditions is briefly summarized. The mild-slope, Boussinesq and action balance equations are compared and analyzed. Th...Recent research on short-term topographic change in the Yangtze Estuary channel under storm surge conditions is briefly summarized. The mild-slope, Boussinesq and action balance equations are compared and analyzed. The action balance equation, SWAN, was used as a wave numerical model to forecast strong storm waves in the Yangtze Estuary. The spherical coordinate system and source terms used in the equation are described in this paper. The significant wave height and the wave orbital motion velocity near the bottom of the channel during 20 m/s winds in the EES direction were simulated, and the model was calibrated with observation data of winds and waves generated by Tropical Cyclone 9912. The distribution of critical velocity for incipient motion along the bottom was computed according to the threshold velocity formula for bottom sediment. The mechanism of rapid deposition is analyzed based on the difference between the root-mean-square value of the near-bottom wave orbital motion velocity and the bottom critical tractive velocity. The results show that a large amount of bottom sediments from Hengsha Shoal and Jiuduan Shoal are lifted into the water body when 20 m/s wind is blowing in the EES direction. Some of the sediments may enter the channel with the cross-channel current, causing serious rapid deposition. Finally, the tendency of the storm to induce rapid deposition in the Yangtze Estuary channel zone is analyzed.展开更多
基金supported by the Science Council,with contract number NSC95-2221-E-006-462Research Center of Ocean Environment and Technology,under the contract NCKU-NSYSU
文摘In this paper the wave action balance equation in terms of frequency-direction spectrum is derived. A theoretical formulation is presented to generate an invariant frequency space to replace the varying wavenumber space through a Jacobian transformation in the wave action balance equation. The physical properties of the Jacobian incorporating the effects of water depths are discussed. The results provide a theoretical basis of wave action balance equations and ensure that the wave balance equations used in the SWAN or other numerical models are correct. It should be noted that the Jacobian is omitted in the wave action balance equations which are identical to a conventional action balance equation.
基金supported by the Special Fund of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2009585812)the National Natural Science Foundation of China(Grant No.50979033)the Programfor New Century Excellent Talentsin University of China(Grant No.NCET-07-0255)
文摘Two different methods for incorporating diffraction effect into wave action balance equation based coastal spectral wave models, WABED and SWAN, are discussed and evaluated with respect to their formulations, numerical implementations, and modeling capabilities. Both models were nm to simulate the wave transformation through a gap between two infinitely long breakwaters and that across an elliptical shoal observed in laboratory studies, with the emphasis laid on the diffraction induced by either obstacles or wave amplitude variations. Calculations of WABED were compared with Sommerfeld＇s analytical solutions, experimental observations and SWAN simulations. It is shown that both methods can predict reasonably wave diffraction for the two eases studied herein, and a fairly better performance is provided by WABED for stronger diffraction ease.
基金supported by the National Natural Science Foundation of China (Grant No. 50779015)
文摘Recent research on short-term topographic change in the Yangtze Estuary channel under storm surge conditions is briefly summarized. The mild-slope, Boussinesq and action balance equations are compared and analyzed. The action balance equation, SWAN, was used as a wave numerical model to forecast strong storm waves in the Yangtze Estuary. The spherical coordinate system and source terms used in the equation are described in this paper. The significant wave height and the wave orbital motion velocity near the bottom of the channel during 20 m/s winds in the EES direction were simulated, and the model was calibrated with observation data of winds and waves generated by Tropical Cyclone 9912. The distribution of critical velocity for incipient motion along the bottom was computed according to the threshold velocity formula for bottom sediment. The mechanism of rapid deposition is analyzed based on the difference between the root-mean-square value of the near-bottom wave orbital motion velocity and the bottom critical tractive velocity. The results show that a large amount of bottom sediments from Hengsha Shoal and Jiuduan Shoal are lifted into the water body when 20 m/s wind is blowing in the EES direction. Some of the sediments may enter the channel with the cross-channel current, causing serious rapid deposition. Finally, the tendency of the storm to induce rapid deposition in the Yangtze Estuary channel zone is analyzed.
