The sea area east of Chenshan Cape has peak tidal current flows that exceed 2.3 m s^-1,which make it a promising site for the development of tidal current energy.Before these resources can be exploited,a comprehensive...The sea area east of Chenshan Cape has peak tidal current flows that exceed 2.3 m s^-1,which make it a promising site for the development of tidal current energy.Before these resources can be exploited,a comprehensive assessment is needed of the potential environmental impacts of the extraction of this energy.In this paper,we describe our construction of a three-dimensional hydrodynamic model of the waters near Chengshan Cape,and verify the performance of the model using continuous data measured in situ.We modeled the potential impacts of the exploitation of these resources on the flow field by adding a momentum loss term in the governing equation of the model.Simulation results show that an assumed tidal farm with an estimated power output of 20.34 MW would have a significant impact on the surrounding water level,especially next to the farm,where fluctuation could reach 6 cm.The maximum drop in the flow velocity in the wake of the farm was predicted to be more than 0.8 m s^-1,and this influence would extend 10 km downstream.展开更多
A process-based 3-D hydrodynamic model is established to simulate the rip current structures under irregular bathymetry. The depth-varying wave-induced residual momentum, the surface rollers, the turbulent mixing and ...A process-based 3-D hydrodynamic model is established to simulate the rip current structures under irregular bathymetry. The depth-varying wave-induced residual momentum, the surface rollers, the turbulent mixing and the wave-current interactions are considered. Experimental datasets are used to validate the model, and it is shown that the model can effectively describe the 3-D structures of the rip currents in both normal and oblique wave incident cases. The flow patterns of the rip currents see various characteristics for different incident wave directions. In the normal incident case, pairs of counter-rotating primary circulation cells are formed, and an offshore rip flow occurs in the embayment troughs. The peak seaward velocities occur at the top of the bed boundary layer, and the undertow is incorporated in addition to the rip currents. In the oblique incident case, the longshore currents are dominant, which result in a meandering flow along the depth contour, and the undertow is weaker compared to that in the normal incident condition.展开更多
Natural rivers are usually winding with branches and shoals, which are difficult to be simulated with rectangular grids. A 3-D current numerical model was established based on the orthogonal curvilinear coordinate sys...Natural rivers are usually winding with branches and shoals, which are difficult to be simulated with rectangular grids. A 3-D current numerical model was established based on the orthogonal curvilinear coordinate system and vertical o coordinate system. The equations were discretisized using a semi-implicit scheme. The ＂predictor＂ and ＂corrector＂ steps were applied for the horizontal momentum equations to meet the basic requirement that the depth-integrated currents obtained from the equations for 2-D and 3-D modes have identical values. And a modification of traditional method of dry/wet discriminance was proposed to determine accurately the boundary and ensure the continuity of variable boundary in the simulation. This model was verified with the data measured in a winding tidal river with branches in April, 2004. The simulated data of water levels and velocities agree well with the measured ones, and the computed results reveal well the practical flow characteristics, including the vertical secondary flow in a winding reach.展开更多
A 3-D impedance method has been introduced to compute the electric currents induced in a human body exposed to extremely low-frequency electromagnetic field. The 3-D impedance method has been deduced from Maxwell equa...A 3-D impedance method has been introduced to compute the electric currents induced in a human body exposed to extremely low-frequency electromagnetic field. The 3-D impedance method has been deduced from Maxwell equations and is put into the computation and simulation effectively to the visible human body model, which has 196×114×626 cells and more than 40 types of tissues. As the result, two representative cases are investigated. One is exposure of the human body to 100 μT （1 000 mG）, the limit recommended by the International Commission on Non-Ionizing Radiation Protection for the public and the other one is the exposure of human body to 0.4 laT （4 mG）, the level at which a statistical link appears with a doubled risk of development of childhood leukaemia. The distribution of induced current density can be obtained and the maximum of induced current are found to be 16 mA/m^2 and 0.07 mA/m^2.展开更多
Spatial hydrographic data collected from August 2007 through May 2008 and the Princeton Ocean Model(POM)are utilized to explain and document the upwelling in the south eastern Arabian Sea(SEAS).The decrease in the mag...Spatial hydrographic data collected from August 2007 through May 2008 and the Princeton Ocean Model(POM)are utilized to explain and document the upwelling in the south eastern Arabian Sea(SEAS).The decrease in the magnitude of winds towards the coast favors local anticyclonic vorticity,resulting in the formation of cyclonic eddy and reversal of coastal currents.The Ekman transport due to alongshore winds,Ekman pumping due to wind stress curl,cyclonic eddy and southward West Indian Coastal Currents play different roles in the SEAS upwelling.In the offshore,wind stress curl leads to the formation of meso-scale eddies,resulting in Ekman pumping at the center and consequent upwelling.The rapid depth variation on the western side of Quilon Mount intensifies upwelling in the offshore.The upwelling Kelvin waves generated at the equator terminates in the Bay of Bengal and do not contribute to the SEAS upwelling.The possible role of local and remote winds,especially around Sri Lanka on the upwelling dynamics of SEAS is described utilizing POM.The Kelvin waves generated off the coast of Sri Lanka during the active phase of the summer monsoon also contribute to the upwelling dynamics off the west coast of India.展开更多
基金supported by the National Natural Science Foundation of China (No. 51479185)the Major Basic Research Project of Shandong Province (No. ZR 2017ZA0202)
文摘The sea area east of Chenshan Cape has peak tidal current flows that exceed 2.3 m s^-1,which make it a promising site for the development of tidal current energy.Before these resources can be exploited,a comprehensive assessment is needed of the potential environmental impacts of the extraction of this energy.In this paper,we describe our construction of a three-dimensional hydrodynamic model of the waters near Chengshan Cape,and verify the performance of the model using continuous data measured in situ.We modeled the potential impacts of the exploitation of these resources on the flow field by adding a momentum loss term in the governing equation of the model.Simulation results show that an assumed tidal farm with an estimated power output of 20.34 MW would have a significant impact on the surrounding water level,especially next to the farm,where fluctuation could reach 6 cm.The maximum drop in the flow velocity in the wake of the farm was predicted to be more than 0.8 m s^-1,and this influence would extend 10 km downstream.
基金supported by the Central Public Institute Foundation of Tianjin Research Institute for Water Transport Engineering,Ministry of Transport(Grant No.TKS100102)
文摘A process-based 3-D hydrodynamic model is established to simulate the rip current structures under irregular bathymetry. The depth-varying wave-induced residual momentum, the surface rollers, the turbulent mixing and the wave-current interactions are considered. Experimental datasets are used to validate the model, and it is shown that the model can effectively describe the 3-D structures of the rip currents in both normal and oblique wave incident cases. The flow patterns of the rip currents see various characteristics for different incident wave directions. In the normal incident case, pairs of counter-rotating primary circulation cells are formed, and an offshore rip flow occurs in the embayment troughs. The peak seaward velocities occur at the top of the bed boundary layer, and the undertow is incorporated in addition to the rip currents. In the oblique incident case, the longshore currents are dominant, which result in a meandering flow along the depth contour, and the undertow is weaker compared to that in the normal incident condition.
文摘Natural rivers are usually winding with branches and shoals, which are difficult to be simulated with rectangular grids. A 3-D current numerical model was established based on the orthogonal curvilinear coordinate system and vertical o coordinate system. The equations were discretisized using a semi-implicit scheme. The ＂predictor＂ and ＂corrector＂ steps were applied for the horizontal momentum equations to meet the basic requirement that the depth-integrated currents obtained from the equations for 2-D and 3-D modes have identical values. And a modification of traditional method of dry/wet discriminance was proposed to determine accurately the boundary and ensure the continuity of variable boundary in the simulation. This model was verified with the data measured in a winding tidal river with branches in April, 2004. The simulated data of water levels and velocities agree well with the measured ones, and the computed results reveal well the practical flow characteristics, including the vertical secondary flow in a winding reach.
基金This work is supported by the National Natural Science Foundation of China （60671055, 60331010）；Innovation Foundation from Beijing University of Posts and Telecommunications.
文摘A 3-D impedance method has been introduced to compute the electric currents induced in a human body exposed to extremely low-frequency electromagnetic field. The 3-D impedance method has been deduced from Maxwell equations and is put into the computation and simulation effectively to the visible human body model, which has 196×114×626 cells and more than 40 types of tissues. As the result, two representative cases are investigated. One is exposure of the human body to 100 μT （1 000 mG）, the limit recommended by the International Commission on Non-Ionizing Radiation Protection for the public and the other one is the exposure of human body to 0.4 laT （4 mG）, the level at which a statistical link appears with a doubled risk of development of childhood leukaemia. The distribution of induced current density can be obtained and the maximum of induced current are found to be 16 mA/m^2 and 0.07 mA/m^2.
文摘Spatial hydrographic data collected from August 2007 through May 2008 and the Princeton Ocean Model(POM)are utilized to explain and document the upwelling in the south eastern Arabian Sea(SEAS).The decrease in the magnitude of winds towards the coast favors local anticyclonic vorticity,resulting in the formation of cyclonic eddy and reversal of coastal currents.The Ekman transport due to alongshore winds,Ekman pumping due to wind stress curl,cyclonic eddy and southward West Indian Coastal Currents play different roles in the SEAS upwelling.In the offshore,wind stress curl leads to the formation of meso-scale eddies,resulting in Ekman pumping at the center and consequent upwelling.The rapid depth variation on the western side of Quilon Mount intensifies upwelling in the offshore.The upwelling Kelvin waves generated at the equator terminates in the Bay of Bengal and do not contribute to the SEAS upwelling.The possible role of local and remote winds,especially around Sri Lanka on the upwelling dynamics of SEAS is described utilizing POM.The Kelvin waves generated off the coast of Sri Lanka during the active phase of the summer monsoon also contribute to the upwelling dynamics off the west coast of India.
