The analysis of the scabed processes of a muddy coast has been described in this paper. On the basisof the basic differential equation of tidal current and sediment movement influenced by waves, a numerical simulation...The analysis of the scabed processes of a muddy coast has been described in this paper. On the basisof the basic differential equation of tidal current and sediment movement influenced by waves, a numerical simulation system for sediment lifted by waves and transported by tidal currents and scabed processes has been established by using MADI method, and applied to the sea area of Tianjin Port with good results.展开更多
Details are given herein of the current main proposals for tidal energy provision from the Severn Estuary, in the UK, with particular emphasis being focused on the Severn Barrage project, as originally promoted by the...Details are given herein of the current main proposals for tidal energy provision from the Severn Estuary, in the UK, with particular emphasis being focused on the Severn Barrage project, as originally promoted by the Severn Tidal Power Group. In particular, emphasis has focused on assessing the potential hydro-environmental impacts and power outputs of a barrage across the estuary, with an unstructured grid, high resolution, model being developed and applied to the estuary to assess the implications of each of five shortlisted proposed schemes on the hydrodynamic, geomorphologic, flood risk and faecal indicator organism changes within the estuary. An outline is given of recent research on power refinements to the model to assess the options for power generation. The results show that the Severn Barrage has the potential to reduce the tidal currents in a highly dynamic estuary. This leads to the reduction of suspended sediment loads (particularly upstream of the barrage), an increase of light penetration within the water column and, potentially, an increase in the benthic bio-diversity and the level of aquatic life in the estuary. The results also show that the Severn Barrage will reduce markedly the risk of flooding upstream of the barrage and to a lesser extent downstream of the structure. In contrast the alternative options have far less impact on flood risk changes. In addition to the Severn Barrage some results are shown herein for a typical lagoon option, namely the Fleming Lagoon.展开更多
The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic ...The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic and sedimentary environments. In this study the impact was investigated, based on synchronized multi-station data from continuous observations made within and around the culture area. In total, three current velocity profiles were identified inside and on the landward side of the culture area. Based on the current velocity profiles we calculated the boundary layer parameters, the fluxes of erosion/deposition, and the rate of sediment transport in different times at each observation site. Comparison between culture and non-culture periods showed that the presence of suspended kelp caused the reduction in the average flow velocity by approximately 49.5%, the bottom friction velocity by 24.8%, the seabed roughness length by 62.7%, and the shear stress and the flux of resuspended sediment by approximately 50%. From analyses in combination with the corresponding vertical variation of the suspended sediment distribution, it is revealed that the lifted sediments by resuspension is mixed with the upper suspended material, which will modify the regional distribution of suspended sediment. These changes in flow structure and sediment movement will accelerate seabed siltation, which corresponds to the changes in seabed erosion/deposition. However, under the influences of the seasonal changes in kelp growth the magnitude of change with the seabed siltation was not obvious inside the culture area, but a fundamental change was apparent around the culture area.展开更多
A particular porosity method named ＂slot method＂ is implemented in a depth-integrated shallow water flow model （DIVAST） to simulate wetting and drying processes. Discussed is the relationship between the shape fac...A particular porosity method named ＂slot method＂ is implemented in a depth-integrated shallow water flow model （DIVAST） to simulate wetting and drying processes. Discussed is the relationship between the shape factors of the ＂slot＂ and the preset depth used in ＂wetting-drying＂ algorithm. Two typical tests are conducted to examine the performance of the method with the effect of the shape factors of the ＂slot＂ being checked in detail in the first test. Numerical results demonstrate that： 1 ） no additional effort to improve the finite difference scheme is needed to implement ＂slot method＂ in DIVAST, and 2） ＂slot method＂ will simulate wetting and diying processes correctly if the shape factors of the ＂slot＂ being selected properly.展开更多
文摘The analysis of the scabed processes of a muddy coast has been described in this paper. On the basisof the basic differential equation of tidal current and sediment movement influenced by waves, a numerical simulation system for sediment lifted by waves and transported by tidal currents and scabed processes has been established by using MADI method, and applied to the sea area of Tianjin Port with good results.
基金Supported by the Flood Risk Management Research Consortium (PhaseⅡ)the UK Engineering and Physical Sciences Research Council (GR/S76304)the Welsh Assembly Government European Regional Development Fund, Project HE09
文摘Details are given herein of the current main proposals for tidal energy provision from the Severn Estuary, in the UK, with particular emphasis being focused on the Severn Barrage project, as originally promoted by the Severn Tidal Power Group. In particular, emphasis has focused on assessing the potential hydro-environmental impacts and power outputs of a barrage across the estuary, with an unstructured grid, high resolution, model being developed and applied to the estuary to assess the implications of each of five shortlisted proposed schemes on the hydrodynamic, geomorphologic, flood risk and faecal indicator organism changes within the estuary. An outline is given of recent research on power refinements to the model to assess the options for power generation. The results show that the Severn Barrage has the potential to reduce the tidal currents in a highly dynamic estuary. This leads to the reduction of suspended sediment loads (particularly upstream of the barrage), an increase of light penetration within the water column and, potentially, an increase in the benthic bio-diversity and the level of aquatic life in the estuary. The results also show that the Severn Barrage will reduce markedly the risk of flooding upstream of the barrage and to a lesser extent downstream of the structure. In contrast the alternative options have far less impact on flood risk changes. In addition to the Severn Barrage some results are shown herein for a typical lagoon option, namely the Fleming Lagoon.
基金funded by the National Natural Science Foundation of China, Nos.41076031 and 41106041
文摘The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic and sedimentary environments. In this study the impact was investigated, based on synchronized multi-station data from continuous observations made within and around the culture area. In total, three current velocity profiles were identified inside and on the landward side of the culture area. Based on the current velocity profiles we calculated the boundary layer parameters, the fluxes of erosion/deposition, and the rate of sediment transport in different times at each observation site. Comparison between culture and non-culture periods showed that the presence of suspended kelp caused the reduction in the average flow velocity by approximately 49.5%, the bottom friction velocity by 24.8%, the seabed roughness length by 62.7%, and the shear stress and the flux of resuspended sediment by approximately 50%. From analyses in combination with the corresponding vertical variation of the suspended sediment distribution, it is revealed that the lifted sediments by resuspension is mixed with the upper suspended material, which will modify the regional distribution of suspended sediment. These changes in flow structure and sediment movement will accelerate seabed siltation, which corresponds to the changes in seabed erosion/deposition. However, under the influences of the seasonal changes in kelp growth the magnitude of change with the seabed siltation was not obvious inside the culture area, but a fundamental change was apparent around the culture area.
基金the National Natural Science Foundation of China (Grant No.10702050)the Natural Science Foundation of Tianjin (Grant No.07JCYBJC07500)the Support Plan of Science and Technology of Tianjin (Grant No.07ZCGYSH01700)
文摘A particular porosity method named ＂slot method＂ is implemented in a depth-integrated shallow water flow model （DIVAST） to simulate wetting and drying processes. Discussed is the relationship between the shape factors of the ＂slot＂ and the preset depth used in ＂wetting-drying＂ algorithm. Two typical tests are conducted to examine the performance of the method with the effect of the shape factors of the ＂slot＂ being checked in detail in the first test. Numerical results demonstrate that： 1 ） no additional effort to improve the finite difference scheme is needed to implement ＂slot method＂ in DIVAST, and 2） ＂slot method＂ will simulate wetting and diying processes correctly if the shape factors of the ＂slot＂ being selected properly.
