The rapid development of the automobile industry and the relative lag of the road construction have constituted a prominent contradiction all over the world, particularly, in most of large cities. To cope with it, ele...The rapid development of the automobile industry and the relative lag of the road construction have constituted a prominent contradiction all over the world, particularly, in most of large cities. To cope with it, elevated roads have been built in many cities both at home and abroad. However, traffic jams frequently appear on elevated roads immediately after the completion of their construction. The awkward situation mainly results from the planning bug or the unsuitable control, apart from drastic increase in transportation demand. Elevated roads,展开更多
In this paper, the bottom of the Dianshan Lake was selected as a test sample. The dynamic release of contaminated sediments into the overlying water column was experimentally investigated in an open water channel unde...In this paper, the bottom of the Dianshan Lake was selected as a test sample. The dynamic release of contaminated sediments into the overlying water column was experimentally investigated in an open water channel under different hydrodynamic conditions. The experimental results indicate that the Total Phosphorus （TP） release process can be divided into three stages： rapid release, slow release and equilibration release. In the initial release stage the measured TP concentration changes along the depth. The TP concentration near the sediment-water interface is higher than that near the water surface, but the TP concentration becomes uniform along the depth after 3 h. The dynamic release of re-suspension sediment pollutants is about 6 times higher than the static release of sediment-water interface. There are three main types of release mechanism： diffusion release, re-suspended pore water mixing release and re-suspended particles desorbing release.展开更多
The joint effects of the sediment size and porosity on the contaminant adsorption/desorption and interfacial diffusion characteristics were experimentally investigated. The adsorption of Phosphorus （P） on the natura...The joint effects of the sediment size and porosity on the contaminant adsorption/desorption and interfacial diffusion characteristics were experimentally investigated. The adsorption of Phosphorus （P） on the natural and artificial sediment suspensions was measured with respect to the P adsorption isotherms and kinetics in the experiment. The obtained adsorption isotherms for different grain-sized sediment suspensions fit well with the Langmuir equation, dependent on the initial aqueous concentration and sediment content. The P kinetic adsorption behaviors for cohesive fine-grained and non-cohesive coarse-grained sediment suspensions clearly show the size-dependent feature. On the other hand, the P kinetic release feature of a porous sediment layer is affected by not only the direct desorption of the uppermost sediments, but also the diffusivity in the pore-water within the underlying sediment layer, characterized by the sediment size and porosity, respectively. Furthermore, the temporal contaminant release from the permeable sediment layer into the overlying water column increases with the increasing flow velocity, while this enhancement in mediating the interfacial diffusion flux is somewhat insignificant in an immediate release stage, largely due to the resistance of the diffusive boundary layer on the hydrodynamic disturbance.展开更多
The time-varying viscosity of common grout and the controllable grout are measured with a rotation viscometer in experiments. The time-varying viscosity of grout is analyzed according to the characteristics in the pro...The time-varying viscosity of common grout and the controllable grout are measured with a rotation viscometer in experiments. The time-varying viscosity of grout is analyzed according to the characteristics in the process of anti-seepage treatment for gravel foundation. The principle of effective stress for porous medium is applied to analyzes the fluid-structure coupling in grouting. In the consideration of coupling physical variables, dynamic models of porosity, permeability and viscosity are constructed. The diffusion radius can thus be defined by the foundational porosity. The distribution of holes in field experiments is designed according to the diffusion radius of grout. Then, the permeability test is designed to verify the grout effect. The calculated diffusion radius coincides with experimental results, and the permeability meets the requirements of the project, which is valuable for the anti-seepage treatment in gravel foundation.展开更多
The three-dimensional vortical structures for an impinging transverse jet in the near region were numerically investigated by means of Large-Eddy Simulation （LES）. The LES results reproduced the skewed jet shear lay...The three-dimensional vortical structures for an impinging transverse jet in the near region were numerically investigated by means of Large-Eddy Simulation （LES）. The LES results reproduced the skewed jet shear layer vortices close to the jet nozzle and the scarf vortex in the near-wall zone in good agreement with the experimental observations. Different vortical modes in the skewed jet shear layer close to the jet nozzle were identified depending upon the velocity ratio between jet and crossflow, namely changing from an approximately axisymmetric mode to a helical one with the velocity ratios varying from 20 to 8. Moreover, the scarf vortex wrapped around the impinging jet in the near-wall zone showed distinct asymmetry with regard to its bilateral spiral legs within the near region. And the entrainment of the ambient crossflow fluids by the scarf vortex in the near-wall zone was appreciably influenced by its asymmetry and in a large part occurred on the surface of the spiral roller structures in the course of spreading downstream.展开更多
The vortex formation and entrainment characteristics for a round transverse jet in shallow water were experimentally investigated by means of a combination of LIF flow visualization and PIV measurement. A scarf vortex...The vortex formation and entrainment characteristics for a round transverse jet in shallow water were experimentally investigated by means of a combination of LIF flow visualization and PIV measurement. A scarf vortex wrapped around the main body of the jet is formed in the near-wall region due to the interaction between the resulting wall jet and sufficiently shallow crossflow, with some more or less unsteady flow properties and with spreading ranges as functions of both the velocity ratio and the water depth within the near field. The entrainment of the ambient crossflow fluid into the jet main body is closely associated with the time-evolving features of the shear layer between the jet and surrounding fluid as well as the induced vortical structures near the wall. In the case of slight impingement upon the wall, the interaction between the jet shear layer and the weak, unstable scarf vortex gives rise to an appreciable local entrainment enhancement, confined in the near-wall region in the vicinity of the stagnation point. While in the case of intense impingement upon the wall, the well-organized and stable scarf vortex gives rise to a greatly enhanced entrainment and a greatly increased lateral spreading rate nearly throughout the overall near field as compared to the conventional wall jet. In addition, the entrainment of the ambient crossflow fluid by the scarf vortex in this case occurs largely on the surface of the unique spiral roller structure by itself due to the presence of smaller and unorganized eddies, and accordingly the scarf vortex is likely to keep its spiral roller structure steadily to a relatively great downstream distance within the near field.展开更多
A new numerical scheme for solving the tidal flow in an opening channel using the advective-diffusion shallow-water equations as the governing equations is proposed based on the combination of the MacCormack and the f...A new numerical scheme for solving the tidal flow in an opening channel using the advective-diffusion shallow-water equations as the governing equations is proposed based on the combination of the MacCormack and the finite analysis methods. In the present scheme, the finite analysis method is used to discretize the momentum equation and the MacCormack technique is used to discretize the continuity equation in a single grid system. The matrix of the discretized momentum equation is characterized by predominantly main diagonal elements, which ensures favorable convergence and stability for the numerical simulation by the combined method. To verify the present method, hydraulics simulation is carried out for a section down mainstream of the Huangpu River. The computational results agree with the measured data. By use of orthogonal curvilinear coordinate system, the methods can be easily extended to the numerical simulation of the tidal flow in a tortuous channel.展开更多
By using the high-efficiency of four-stage calculation method named ＂channel-junction-channel＂ and considering the influence of temporal and spatial variation of aquatic environmental capacity, an optimization metho...By using the high-efficiency of four-stage calculation method named ＂channel-junction-channel＂ and considering the influence of temporal and spatial variation of aquatic environmental capacity, an optimization method of aquatic environmental capacity for tidal river network was worked out. The method not only reflects characteristics of unsteady flow with variable directions, but also indicates that aquatic environmental capacity is influenced by boundary condition and water quality standard, etc. It has been applied to the regional program of Pudong area in Shanghai, and the computed results agree well with the practical data.展开更多
Based on particle approach and tidal flow model this article studies the behavior of the oil slick on the water surface in the Huangpu River, a tidal waterway in Shanghai. In order to track the oil slick motion, a two...Based on particle approach and tidal flow model this article studies the behavior of the oil slick on the water surface in the Huangpu River, a tidal waterway in Shanghai. In order to track the oil slick motion, a two-dimensional oil trajectory model is used. The dynamical properties of spilled oil characterized by advection, oil spreading and turbulent diffusion are considered in the model. The simulation results consistent with the flume experimental data show that the model is applicable. Both simulation and experiment illustrate that the tidal flow has a great influence on the oil slick motion. The calculated results can be used as a reference for the response to oil spill accidents in rivers.展开更多
文摘The rapid development of the automobile industry and the relative lag of the road construction have constituted a prominent contradiction all over the world, particularly, in most of large cities. To cope with it, elevated roads have been built in many cities both at home and abroad. However, traffic jams frequently appear on elevated roads immediately after the completion of their construction. The awkward situation mainly results from the planning bug or the unsuitable control, apart from drastic increase in transportation demand. Elevated roads,
基金the National Natural Science Foundation of China (Grant Nos. 10972134, 11032007)the Shanghai Program for Innovative Research Team in Universities
文摘In this paper, the bottom of the Dianshan Lake was selected as a test sample. The dynamic release of contaminated sediments into the overlying water column was experimentally investigated in an open water channel under different hydrodynamic conditions. The experimental results indicate that the Total Phosphorus （TP） release process can be divided into three stages： rapid release, slow release and equilibration release. In the initial release stage the measured TP concentration changes along the depth. The TP concentration near the sediment-water interface is higher than that near the water surface, but the TP concentration becomes uniform along the depth after 3 h. The dynamic release of re-suspension sediment pollutants is about 6 times higher than the static release of sediment-water interface. There are three main types of release mechanism： diffusion release, re-suspended pore water mixing release and re-suspended particles desorbing release.
基金Project supported by the National Natural Science Foundation of China(Grant Nos. 10972134, 11032007)the Shanghai key Laboratory of mechanics in energy Engineering and the Shanghai Program for Innovative Research Team in Universities
文摘The joint effects of the sediment size and porosity on the contaminant adsorption/desorption and interfacial diffusion characteristics were experimentally investigated. The adsorption of Phosphorus （P） on the natural and artificial sediment suspensions was measured with respect to the P adsorption isotherms and kinetics in the experiment. The obtained adsorption isotherms for different grain-sized sediment suspensions fit well with the Langmuir equation, dependent on the initial aqueous concentration and sediment content. The P kinetic adsorption behaviors for cohesive fine-grained and non-cohesive coarse-grained sediment suspensions clearly show the size-dependent feature. On the other hand, the P kinetic release feature of a porous sediment layer is affected by not only the direct desorption of the uppermost sediments, but also the diffusivity in the pore-water within the underlying sediment layer, characterized by the sediment size and porosity, respectively. Furthermore, the temporal contaminant release from the permeable sediment layer into the overlying water column increases with the increasing flow velocity, while this enhancement in mediating the interfacial diffusion flux is somewhat insignificant in an immediate release stage, largely due to the resistance of the diffusive boundary layer on the hydrodynamic disturbance.
基金supported by the Shanghai Leading Academic Discipline Project (Grant No.S30106)the Shanghai Program for Innovation Research Team in Universities
文摘The time-varying viscosity of common grout and the controllable grout are measured with a rotation viscometer in experiments. The time-varying viscosity of grout is analyzed according to the characteristics in the process of anti-seepage treatment for gravel foundation. The principle of effective stress for porous medium is applied to analyzes the fluid-structure coupling in grouting. In the consideration of coupling physical variables, dynamic models of porosity, permeability and viscosity are constructed. The diffusion radius can thus be defined by the foundational porosity. The distribution of holes in field experiments is designed according to the diffusion radius of grout. Then, the permeability test is designed to verify the grout effect. The calculated diffusion radius coincides with experimental results, and the permeability meets the requirements of the project, which is valuable for the anti-seepage treatment in gravel foundation.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10572084)Shanghai Leading Academic Discipline Project (Grant No. Y0103)
文摘The three-dimensional vortical structures for an impinging transverse jet in the near region were numerically investigated by means of Large-Eddy Simulation （LES）. The LES results reproduced the skewed jet shear layer vortices close to the jet nozzle and the scarf vortex in the near-wall zone in good agreement with the experimental observations. Different vortical modes in the skewed jet shear layer close to the jet nozzle were identified depending upon the velocity ratio between jet and crossflow, namely changing from an approximately axisymmetric mode to a helical one with the velocity ratios varying from 20 to 8. Moreover, the scarf vortex wrapped around the impinging jet in the near-wall zone showed distinct asymmetry with regard to its bilateral spiral legs within the near region. And the entrainment of the ambient crossflow fluids by the scarf vortex in the near-wall zone was appreciably influenced by its asymmetry and in a large part occurred on the surface of the spiral roller structures in the course of spreading downstream.
基金supported by the National Natural Science Foundation of China (Grant No. 10572084)the Shanghai Pujiang Program (Grant No. 08PJ14054)the Innovation Program of Shanghai Municipal Education Commission (Grant No. 09 YZ01)
文摘The vortex formation and entrainment characteristics for a round transverse jet in shallow water were experimentally investigated by means of a combination of LIF flow visualization and PIV measurement. A scarf vortex wrapped around the main body of the jet is formed in the near-wall region due to the interaction between the resulting wall jet and sufficiently shallow crossflow, with some more or less unsteady flow properties and with spreading ranges as functions of both the velocity ratio and the water depth within the near field. The entrainment of the ambient crossflow fluid into the jet main body is closely associated with the time-evolving features of the shear layer between the jet and surrounding fluid as well as the induced vortical structures near the wall. In the case of slight impingement upon the wall, the interaction between the jet shear layer and the weak, unstable scarf vortex gives rise to an appreciable local entrainment enhancement, confined in the near-wall region in the vicinity of the stagnation point. While in the case of intense impingement upon the wall, the well-organized and stable scarf vortex gives rise to a greatly enhanced entrainment and a greatly increased lateral spreading rate nearly throughout the overall near field as compared to the conventional wall jet. In addition, the entrainment of the ambient crossflow fluid by the scarf vortex in this case occurs largely on the surface of the unique spiral roller structure by itself due to the presence of smaller and unorganized eddies, and accordingly the scarf vortex is likely to keep its spiral roller structure steadily to a relatively great downstream distance within the near field.
基金supported by the National Natural Science Foundation of China (Grant No.10572084)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No.20050280008)
文摘A new numerical scheme for solving the tidal flow in an opening channel using the advective-diffusion shallow-water equations as the governing equations is proposed based on the combination of the MacCormack and the finite analysis methods. In the present scheme, the finite analysis method is used to discretize the momentum equation and the MacCormack technique is used to discretize the continuity equation in a single grid system. The matrix of the discretized momentum equation is characterized by predominantly main diagonal elements, which ensures favorable convergence and stability for the numerical simulation by the combined method. To verify the present method, hydraulics simulation is carried out for a section down mainstream of the Huangpu River. The computational results agree with the measured data. By use of orthogonal curvilinear coordinate system, the methods can be easily extended to the numerical simulation of the tidal flow in a tortuous channel.
基金Project supported by Shanghai Leading Academic Discipline Project (Grant No: Y0103).
文摘By using the high-efficiency of four-stage calculation method named ＂channel-junction-channel＂ and considering the influence of temporal and spatial variation of aquatic environmental capacity, an optimization method of aquatic environmental capacity for tidal river network was worked out. The method not only reflects characteristics of unsteady flow with variable directions, but also indicates that aquatic environmental capacity is influenced by boundary condition and water quality standard, etc. It has been applied to the regional program of Pudong area in Shanghai, and the computed results agree well with the practical data.
基金supported by the National Natural Science Foundation of China (Grant No.10972134)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No.20050280008)
文摘Based on particle approach and tidal flow model this article studies the behavior of the oil slick on the water surface in the Huangpu River, a tidal waterway in Shanghai. In order to track the oil slick motion, a two-dimensional oil trajectory model is used. The dynamical properties of spilled oil characterized by advection, oil spreading and turbulent diffusion are considered in the model. The simulation results consistent with the flume experimental data show that the model is applicable. Both simulation and experiment illustrate that the tidal flow has a great influence on the oil slick motion. The calculated results can be used as a reference for the response to oil spill accidents in rivers.
