The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, ma...The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.展开更多
Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In t...Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R^2 value ～96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of "torque" or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed.展开更多
Modeling two-dimensional overland flow across complex real-world topography is a challenging problem. Predicting the overland flow variables for various whatif rainfall scenarios can facilitate designing water infrast...Modeling two-dimensional overland flow across complex real-world topography is a challenging problem. Predicting the overland flow variables for various whatif rainfall scenarios can facilitate designing water infrastructure components aimed at preventing inundation and urban flooding. Numerical models that are being used range from those that solve the simplified St. Venant equations to CFD models that solve the complete three dimensional Navier-Stokes equations. In this work, the performance of the USGS Diffusion Hydrodynamic Model (DHM) for a series of overland flow test problems was tested by comparing numerical solutions obtained for an event-driven simulation across various sensitive parameter combinations. The reliability of the model and its ability to incorporate various topographical characteristics in the domain are illustrated.展开更多
A real-time mathematical model for two dimensional tidal flow and water quality is presented in this paper. The control-volume-based-finite-difference method and the 'power interpolation distribution' advocate...A real-time mathematical model for two dimensional tidal flow and water quality is presented in this paper. The control-volume-based-finite-difference method and the 'power interpolation distribution' advocated by Patankar [4] have been employed, and new boundary condition for tidal flow is recommended. The model is un- conditionally stable and convergent, and able to deal with irregular estuarine topography and movable boundary problems. Practical application of the model is illustrated by an example for the Swatou Bay. A fair agreement be- tween the values measured and computed demonstrates the validity of the model developed.展开更多
文章采用FLOW-3D软件,通过RNGk-ε模型和volume of fluid(VOF)方法相结合,实现了竖井水平旋流泄洪洞水力特性的三维水流流场数值模拟;对开敞式进水口轴线与旋流洞轴线交角不同时起旋室的压强分布、旋流角和紊动能等水力特性进行了对比...文章采用FLOW-3D软件,通过RNGk-ε模型和volume of fluid(VOF)方法相结合,实现了竖井水平旋流泄洪洞水力特性的三维水流流场数值模拟;对开敞式进水口轴线与旋流洞轴线交角不同时起旋室的压强分布、旋流角和紊动能等水力特性进行了对比分析研究,数值模拟能够客观地反映起旋室旋流的流场特性,成果可为旋流溢洪道的研究应用提供参考.展开更多
A three-dimensional hydrodynamic model is presented which combines a terrain-following vertical coordinate with a horizontally orthogonal curvilinear coordinate system to fit the complex bottom topography and coastlin...A three-dimensional hydrodynamic model is presented which combines a terrain-following vertical coordinate with a horizontally orthogonal curvilinear coordinate system to fit the complex bottom topography and coastlines near estuaries, continental shelves, and harbors. To solve the governing equations more efficiently, we improve the alternating direction implicit method, which is extensively used in the numerical modeling of horizontal two-dimensional shallow water equations, and extend it to a three-dimensional tidal model with relatively little computational effort. Through several test cases and realistic applications, as presented in the paper, it can be demonstrated that the model is capable of simulating the periodic to-and-fro currents, wind-driven flow, Ekman spirals, and tidal currents in the near-shore region.展开更多
Computational modeling continues to evolve in applications of hydrology and hydraulics, and the field of Computational Hydrology and Hydraulics has grown into a significant technology in both engineering and computati...Computational modeling continues to evolve in applications of hydrology and hydraulics, and the field of Computational Hydrology and Hydraulics has grown into a significant technology in both engineering and computational mathematics. In this paper, the fundamental issue of assessment of computational error is addressed by determination of an “equivalent” mathematical statement, as a partial differential equation (“PDE”) that describes the original mathematical PDE statement and computational solution of it. In other words, given that the computational model does not exactly solve the governing PDE and that the computational processes used to approximate the governing PDE further moves the computational outcome away from the exact solution, what “alternate” or “equivalent” PDE does the resulting computational model exactly solve? In this paper it is shown that development of such an equivalent PDE enables an assessment of computational error by direct comparison of the equivalent PDE to the original PDE targeted to being solved. As an example, the USGS Diffusion Hydrodynamic Model (“DHM”) is examined as to development of an equivalent PDE that describes the DHM computational modeling outcome, which is then compared to the actual outcomes resulting from application of the DHM model.展开更多
A three dimensional numerical model based on the Reynolds equations is presented that can be used to predict the surface water flow in open channels.The model uses a computational mesh that conforms to the free water ...A three dimensional numerical model based on the Reynolds equations is presented that can be used to predict the surface water flow in open channels.The model uses a computational mesh that conforms to the free water sur- face and the bottom of the channel so that the accuracy of boundary condition application,code complexity,and e- conomy could be enhanced.The k-ε turbulence model is used to estimate the eddy viscosity coefficient.Instead of using the“rigid-lid”approximation a 2-D equation derived from integrating the continuity equation over the total depth is adopted to determine the elevation of the free water surface.A new algorithm is presented based on the conventional SIMPLE procedure.The block correction technique is employed to enhance rate of convergence. The model presented is applied to a bottom discharge into a rectangular straight channel for three dimensional phenomena to obtain the free water surface configuration,velocities and pressure.The computed results are in good agreement with the previous experimental values.展开更多
This Paper concerns with the numerical modelling of flow field in a tidal river and in the vicinity of intake of a nuclear power plant. The hybrid method of fractional steps presented in [1] was adopted in this modell...This Paper concerns with the numerical modelling of flow field in a tidal river and in the vicinity of intake of a nuclear power plant. The hybrid method of fractional steps presented in [1] was adopted in this modelling. In order to simulate the local flow field nearby the water intake meticulously, the technique of the match of the coarse and fine grids was used. The numerical results are in good agreement with the in-situ measurements of the main current. The detailed data of local flow field nearby the intake provides the assessment of the sediment transport characteristics in the vicinity of intake of the nuclear power plant.展开更多
基金The Natural Science Foundation of Tianjin, China under contract No.08JCZDZT00200
文摘The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.
基金The National Key R&D Project of China under contract No.2017YFC1404201the USA North Pacific Research Board Project under contract No.1229the USA Bureau of Ocean Energy Management Awards under contract Nos M12PG00024(ACES)and M12PG00018(Arctic EIS)
文摘Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R^2 value ～96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of "torque" or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed.
文摘Modeling two-dimensional overland flow across complex real-world topography is a challenging problem. Predicting the overland flow variables for various whatif rainfall scenarios can facilitate designing water infrastructure components aimed at preventing inundation and urban flooding. Numerical models that are being used range from those that solve the simplified St. Venant equations to CFD models that solve the complete three dimensional Navier-Stokes equations. In this work, the performance of the USGS Diffusion Hydrodynamic Model (DHM) for a series of overland flow test problems was tested by comparing numerical solutions obtained for an event-driven simulation across various sensitive parameter combinations. The reliability of the model and its ability to incorporate various topographical characteristics in the domain are illustrated.
文摘A real-time mathematical model for two dimensional tidal flow and water quality is presented in this paper. The control-volume-based-finite-difference method and the 'power interpolation distribution' advocated by Patankar [4] have been employed, and new boundary condition for tidal flow is recommended. The model is un- conditionally stable and convergent, and able to deal with irregular estuarine topography and movable boundary problems. Practical application of the model is illustrated by an example for the Swatou Bay. A fair agreement be- tween the values measured and computed demonstrates the validity of the model developed.
文摘文章采用FLOW-3D软件,通过RNGk-ε模型和volume of fluid(VOF)方法相结合,实现了竖井水平旋流泄洪洞水力特性的三维水流流场数值模拟;对开敞式进水口轴线与旋流洞轴线交角不同时起旋室的压强分布、旋流角和紊动能等水力特性进行了对比分析研究,数值模拟能够客观地反映起旋室旋流的流场特性,成果可为旋流溢洪道的研究应用提供参考.
基金We appreciate the detailed suggestions and comments provided by the editor and the anonymous reviewers. Several research programs supported the work presented in this article： the National Basic Research Program of China （No. 2015CB954100）, the National Natural Science Foundation of China （Grant No. 41306078）, and the Priority Academic Program Development of Jiangsu Higher Education Institutions （Grant No. 1411109012）.
文摘A three-dimensional hydrodynamic model is presented which combines a terrain-following vertical coordinate with a horizontally orthogonal curvilinear coordinate system to fit the complex bottom topography and coastlines near estuaries, continental shelves, and harbors. To solve the governing equations more efficiently, we improve the alternating direction implicit method, which is extensively used in the numerical modeling of horizontal two-dimensional shallow water equations, and extend it to a three-dimensional tidal model with relatively little computational effort. Through several test cases and realistic applications, as presented in the paper, it can be demonstrated that the model is capable of simulating the periodic to-and-fro currents, wind-driven flow, Ekman spirals, and tidal currents in the near-shore region.
文摘Computational modeling continues to evolve in applications of hydrology and hydraulics, and the field of Computational Hydrology and Hydraulics has grown into a significant technology in both engineering and computational mathematics. In this paper, the fundamental issue of assessment of computational error is addressed by determination of an “equivalent” mathematical statement, as a partial differential equation (“PDE”) that describes the original mathematical PDE statement and computational solution of it. In other words, given that the computational model does not exactly solve the governing PDE and that the computational processes used to approximate the governing PDE further moves the computational outcome away from the exact solution, what “alternate” or “equivalent” PDE does the resulting computational model exactly solve? In this paper it is shown that development of such an equivalent PDE enables an assessment of computational error by direct comparison of the equivalent PDE to the original PDE targeted to being solved. As an example, the USGS Diffusion Hydrodynamic Model (“DHM”) is examined as to development of an equivalent PDE that describes the DHM computational modeling outcome, which is then compared to the actual outcomes resulting from application of the DHM model.
基金This work is supported by Chinese National Natural Science Foundation.
文摘A three dimensional numerical model based on the Reynolds equations is presented that can be used to predict the surface water flow in open channels.The model uses a computational mesh that conforms to the free water sur- face and the bottom of the channel so that the accuracy of boundary condition application,code complexity,and e- conomy could be enhanced.The k-ε turbulence model is used to estimate the eddy viscosity coefficient.Instead of using the“rigid-lid”approximation a 2-D equation derived from integrating the continuity equation over the total depth is adopted to determine the elevation of the free water surface.A new algorithm is presented based on the conventional SIMPLE procedure.The block correction technique is employed to enhance rate of convergence. The model presented is applied to a bottom discharge into a rectangular straight channel for three dimensional phenomena to obtain the free water surface configuration,velocities and pressure.The computed results are in good agreement with the previous experimental values.
文摘This Paper concerns with the numerical modelling of flow field in a tidal river and in the vicinity of intake of a nuclear power plant. The hybrid method of fractional steps presented in [1] was adopted in this modelling. In order to simulate the local flow field nearby the water intake meticulously, the technique of the match of the coarse and fine grids was used. The numerical results are in good agreement with the in-situ measurements of the main current. The detailed data of local flow field nearby the intake provides the assessment of the sediment transport characteristics in the vicinity of intake of the nuclear power plant.
