In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method a...In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method and targeted long narrow reaches of the river networks, while the 2D model targeted broad channels and embayment and solved the 2D shallow-water equations using a semi-implicit scheme applied to an unstructured grid of triangular cells. The 1D and 2D models were solved simultaneously by building a matrix for the free surface elevation at every 1D junction and 2D cell center. Velocities were then computed explicitly based on the results at the previous time step and the updated water level. The originality of the scheme arose from a novel coupling method. The results showed that the coupled 1D/2D model produced identical results as the full 2D model in classical to benchmark problems with considerable savings in computational effort. Application of the model to the Pearl River Estuary in southern China showed that complex patterns of tidal wave propagation could be efficiently modeled.展开更多
In this paper, a revisiting Hughes’ dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimension...In this paper, a revisiting Hughes’ dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimensional continuous walking facility scattered with a circular obstruction. It is assumed that pedestrians prefer to walk a path with the lowest instantaneous travel cost from origin to destination, under the consideration of the current traffic conditions and the tendency to avoid a high-density region and an obstruction. An algorithm for the pedestrian flow model is based on a cellcentered finite volume method for a scalar conservation law equation, a fast sweeping method for an Eikonal-type equation and a second-order TVD Runge-Kutta method for the time integration on unstructured meshes. Numerical results demonstrate the effectiveness of the algorithm. It is verified that density distribution of pedestrian flow is influenced by the position of the obstruction and the path-choice behavior of pedestrians.展开更多
Nearshore currents have a complicated circulation structure over a beach due to the mutual interaction between waves and currents. To investigate the wave-induced circulation over a beach, a three-dimensional unstruct...Nearshore currents have a complicated circulation structure over a beach due to the mutual interaction between waves and currents. To investigate the wave-induced circulation over a beach, a three-dimensional unstructured model accounting for the combined actions of waves and currents is established. The wave distribution over the beach is computed by a wave model and the depth-dependent wave radiation stresses with the surface roller are employed in the hydrodynamic model. The present model takes the mixing coefficients and the bottom shear stress under waves and currents into account. To evaluate the three-dimensional unstructured model, the laboratory experiments over a plane and irregular beach are used to test the performance of the model. The undertow over a plane beach is well reproduced and the vertical variability is captured. The performance of the model over an irregular beach is well displayed in the reproduction of pairs of cotmter-rotating primary circulations at the embayment troughs. Meanwhile, the secondary circulations are observed in the swash zone. The model captures the circulation systems over a beach and the circulation structures of the wave-induced currents are well exhibited.展开更多
With the unstructured grid, the Finite Volume Coastal Ocean Model（FVCOM） is converted from its original FORTRAN code to a Compute Unified Device Architecture（CUDA） C code, and optimized on the Graphic Processor U...With the unstructured grid, the Finite Volume Coastal Ocean Model（FVCOM） is converted from its original FORTRAN code to a Compute Unified Device Architecture（CUDA） C code, and optimized on the Graphic Processor Unit（GPU）. The proposed GPU-FVCOM is tested against analytical solutions for two standard cases in a rectangular basin, a tide induced flow and a wind induced circulation. It is then applied to the Ningbo＇s coastal water area to simulate the tidal motion and analyze the flow field and the vertical tide velocity structure. The simulation results agree with the measured data quite well. The accelerated performance of the proposed 3-D model reaches 30 times of that of a single thread program, and the GPU-FVCOM implemented on a Tesla k20 device is faster than on a workstation with 20 CPU cores, which shows that the GPU-FVCOM is efficient for solving large scale sea area and high resolution engineering problems.展开更多
In the present paper,tides in the port of Vancouver Harbour have been investigated with a high-resolution three-dimensional hydrodynamic model based on FVCOM(Finite Volume Community Ocean Model).The model was evaluate...In the present paper,tides in the port of Vancouver Harbour have been investigated with a high-resolution three-dimensional hydrodynamic model based on FVCOM(Finite Volume Community Ocean Model).The model was evaluated against field observations including tidal elevations and tidal currents,and the evaluation showed that the model was in good agreement with the observational data.Using the model,we first investigated the horizontal distributions of tides,tidal currents,and tidally induced residual circulation,and then investigated the tidal asymmetry and dynamic mechanisms of tidal flows in the harbour.The tidal residual circulation shows a strong spatial pattern,which is associated with the local coastlines and variation of topography.The tidal asymmetry in the harbour is caused by different mechanisms,not only including the traditional factors,such as residual flows,the interaction between M_(2)and its overtide M_(4),but also the interaction of principal astronomical tides of O_(1),K_(1),and M_(2).The momentum balance is dominated by terms of the advection and the pressure gradient in First Narrows and Second Narrows,whereas terms of the local acceleration and the Coriolis are also important in the central harbour.The spatial variations of the momentum terms are strongly associated with the local changes in coastline and topography.展开更多
基金financially supporrted by the National Key Research and Development Program of China(Grant No.2017YFC1404200)the National Natural Science Foundation of China(Grant Nos.51779150 and 51979040)
文摘In this study, 1D and 2D shallow-water models were coupled to simulate unsteady flow in channel networks and embayment. The 1D model solved the 1D shallow-water equations (St. Venant) using the Preissmann box method and targeted long narrow reaches of the river networks, while the 2D model targeted broad channels and embayment and solved the 2D shallow-water equations using a semi-implicit scheme applied to an unstructured grid of triangular cells. The 1D and 2D models were solved simultaneously by building a matrix for the free surface elevation at every 1D junction and 2D cell center. Velocities were then computed explicitly based on the results at the previous time step and the updated water level. The originality of the scheme arose from a novel coupling method. The results showed that the coupled 1D/2D model produced identical results as the full 2D model in classical to benchmark problems with considerable savings in computational effort. Application of the model to the Pearl River Estuary in southern China showed that complex patterns of tidal wave propagation could be efficiently modeled.
基金supported by the Natural Science Foundation of Anhui Province (090416227)Chinese Universities Scientific Fund
文摘In this paper, a revisiting Hughes’ dynamic continuum model is used to investigate and predict the essential macroscopic characteristics of pedestrian flow, such as flow, density and average speed, in a two dimensional continuous walking facility scattered with a circular obstruction. It is assumed that pedestrians prefer to walk a path with the lowest instantaneous travel cost from origin to destination, under the consideration of the current traffic conditions and the tendency to avoid a high-density region and an obstruction. An algorithm for the pedestrian flow model is based on a cellcentered finite volume method for a scalar conservation law equation, a fast sweeping method for an Eikonal-type equation and a second-order TVD Runge-Kutta method for the time integration on unstructured meshes. Numerical results demonstrate the effectiveness of the algorithm. It is verified that density distribution of pedestrian flow is influenced by the position of the obstruction and the path-choice behavior of pedestrians.
基金supported by the National Key Basic Research Development Program of China(973 Program,Grant No.2013CB036101)the National Natural Science Foundation of China(Grant No.51379037)
文摘Nearshore currents have a complicated circulation structure over a beach due to the mutual interaction between waves and currents. To investigate the wave-induced circulation over a beach, a three-dimensional unstructured model accounting for the combined actions of waves and currents is established. The wave distribution over the beach is computed by a wave model and the depth-dependent wave radiation stresses with the surface roller are employed in the hydrodynamic model. The present model takes the mixing coefficients and the bottom shear stress under waves and currents into account. To evaluate the three-dimensional unstructured model, the laboratory experiments over a plane and irregular beach are used to test the performance of the model. The undertow over a plane beach is well reproduced and the vertical variability is captured. The performance of the model over an irregular beach is well displayed in the reproduction of pairs of cotmter-rotating primary circulations at the embayment troughs. Meanwhile, the secondary circulations are observed in the swash zone. The model captures the circulation systems over a beach and the circulation structures of the wave-induced currents are well exhibited.
基金Project supported by the National Natural Science Foundation of China(Grant No.51279028,51479175)the Public Science and Technology Research Funds Projects of Ocean(Grant No.201405025)
文摘With the unstructured grid, the Finite Volume Coastal Ocean Model（FVCOM） is converted from its original FORTRAN code to a Compute Unified Device Architecture（CUDA） C code, and optimized on the Graphic Processor Unit（GPU）. The proposed GPU-FVCOM is tested against analytical solutions for two standard cases in a rectangular basin, a tide induced flow and a wind induced circulation. It is then applied to the Ningbo＇s coastal water area to simulate the tidal motion and analyze the flow field and the vertical tide velocity structure. The simulation results agree with the measured data quite well. The accelerated performance of the proposed 3-D model reaches 30 times of that of a single thread program, and the GPU-FVCOM implemented on a Tesla k20 device is faster than on a workstation with 20 CPU cores, which shows that the GPU-FVCOM is efficient for solving large scale sea area and high resolution engineering problems.
基金supported by the Department of Fisheries and Oceans Canada(DFO).
文摘In the present paper,tides in the port of Vancouver Harbour have been investigated with a high-resolution three-dimensional hydrodynamic model based on FVCOM(Finite Volume Community Ocean Model).The model was evaluated against field observations including tidal elevations and tidal currents,and the evaluation showed that the model was in good agreement with the observational data.Using the model,we first investigated the horizontal distributions of tides,tidal currents,and tidally induced residual circulation,and then investigated the tidal asymmetry and dynamic mechanisms of tidal flows in the harbour.The tidal residual circulation shows a strong spatial pattern,which is associated with the local coastlines and variation of topography.The tidal asymmetry in the harbour is caused by different mechanisms,not only including the traditional factors,such as residual flows,the interaction between M_(2)and its overtide M_(4),but also the interaction of principal astronomical tides of O_(1),K_(1),and M_(2).The momentum balance is dominated by terms of the advection and the pressure gradient in First Narrows and Second Narrows,whereas terms of the local acceleration and the Coriolis are also important in the central harbour.The spatial variations of the momentum terms are strongly associated with the local changes in coastline and topography.
