The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the s...The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the solution of model is expanded into a series in powers of perturbation parameter. By using the Boundary Element Method (BEM) and Duhamel principle, wellbore pressure with effects of skins and wellbore storage is obtained. The type curves are plotted and analyzed considering effects of heterogeneity, arbitrary shape and impermeable barriers. Finally, the results obtained by perturbation boundary element method is compared with the analytical solution and is available for the transient pressure analysis of arbitrary shaped reservoirs.展开更多
The increased application of chemical fertilizers in citrus orchards and the non-point source nitrogen(N) and phosphorus(P)diffusion threaten the fresh water quality of the Three Gorges Reservoir area of China. A 10-y...The increased application of chemical fertilizers in citrus orchards and the non-point source nitrogen(N) and phosphorus(P)diffusion threaten the fresh water quality of the Three Gorges Reservoir area of China. A 10-year field trial on sloping citrus lands was conducted to evaluate five protection methods for reducing N and P losses: 1) intercropping with perennial white clover(CW); 2) straw mulching of the soil surface(CS); 3) intercropping with yellow daylily contour hedgerows(CH); 4) an impermeable membrane buried in the soil along the contour lines(CM); and 5) intercropping with a rotation of wheat and peanut(CWP). An area of conventional citrus management was also maintained as the control(CK). The results showed that CM and CH were the most effective methods for reducing surface runoff. The sediment yield were reduced at the highest rate by CW and CH and was also significantly reduced by CS. Reduced runoff volume and sediment yield were the crucial mechanism for the reductions in N and P losses. Compared with the control, CW, CS, CH, and CM reduced annual runoff by 9%, 13%, 25%, and 30%, sediment yield by 77%, 55%, 71%, and 28%,N loss by 10%, 23% 36%, and 37%, and P loss by 39%, 31%, 27%, and 25%, respectively. CW, CS, CH, and CM were effective in reducing N and P losses from the sloping citrus land. However, over the long-term, surface soil nutrient accumulation in CW, CS, and CH diminished the benefit of those methods in reducing N and P losses. In addition, CWP increased soil erosion and nutrient loss,which showed that citrus intercropping with other crops was an unsuitable method for citrus sloping land in the Three Gorges area.展开更多
The Urban Commune of Maradi in Niger experienced increasingly frequent flooding following rainy episodes generating volumes and water flows that are difficult to control in recent years. This study aims to determine t...The Urban Commune of Maradi in Niger experienced increasingly frequent flooding following rainy episodes generating volumes and water flows that are difficult to control in recent years. This study aims to determine the impacts of runoff water in Commune II of Maradi City and to assess the role of urban planning in runoff management, as well as the strengths and weaknesses of urban sanitation in Maradi. The methodological approach used consisted of: 1) an interpretation of documentary data, 2) gathering information on runoff at several sites in the study area, and 3) interviews and questionnaires with local communities. This approach made it possible to understand the degree of vulnerability of the populations to flooding and then to propose sustainable solutions to reduce the vulnerability of the affected populations, through the implementation of effective urban rainwater management practices (USWMP). The results show that the impacts of runoff are mainly related to the lack of adequate storm water drainage networks in the area, but also to the nature of the habitats. Geomorphological factors such as the nature of the soil, the slope of the terrain and the altitude increase the degree of risk. In addition, the inadequacy and dilapidation of the drainage systems of the canals and above all the anarchic occupation of the land linked to accelerated urbanization are the cause of flooding by stagnation of rainwater. A phenomenon now linked to numerous deteriorations of urban equipment, the runoff of rainwater in the city of Maradi carries so many pollutants that municipalities, businesses and individuals should put in place pollution prevention measures.展开更多
The steady-state flow mathematical model of arbitrary shaped homogeneous reservoirs with impermeable barrier is constructed in this paper. By using Boundary Element Method （BEM）, the mathematical model is solved. An...The steady-state flow mathematical model of arbitrary shaped homogeneous reservoirs with impermeable barrier is constructed in this paper. By using Boundary Element Method （BEM）, the mathematical model is solved. And a streamline generating technique is presented. The figures of streamlines are plotted and analyzed considering the effect of complex boundary and impermeable barriers. Through analyzing it indicates that the size, shape and orientation of impermeable barriers have various degree of influence on the streamlines. So, if there are impermeable barriers in reservoir according to the geological materials, the influence of impermeable barriers must be considered when adjusting flood pattern and injection strategy.展开更多
A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreb...A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: (1) perfect workability: slump is more than 22cm, theslump afar 3h is about 16cm; (2) high impermeability:for the mortar, the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2. 2cm;(3) high crack-resistance: there is a micro-expansion at the age of 90d; (4) high compressivestrength: compared with the controlled concrete, the compressive strengths at the age of 3d and 2Sd are improved by 66.4% and 62.0% , respectively. At the same time, the effects of different curing condition on mortar and concrete expansive andshrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism, was investigatedin the present paper.展开更多
Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled ...Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled discrete element method(DEM)and computational fluid dynamics(CFD)approach is adopted to model suffusion in multi-layered soils with different fines contents,and soils with one or more impermeable zones.The parameters of the CFD-DEM model are first calibrated with the classic Ergun test and a good match with experiment is obtained.Then suffusion in multi-layered soils with different fines contents and impermeable zones is simulated and discussed.The simulation results show that,for soils with multiple layers,the cumulative eroded mass is mainly determined by the fines content of the bottom layer.In general,the higher the fines content of the bottom soil layer,the higher the cumulative eroded mass.In addition,suffusion is more severe if the fines content of the layer above is decreased.Impermeable zones inside soil specimens can increase the flow velocity around those zones,facilitating the migration of fine particles and intensifying suffusion.展开更多
Domain switching around electrically permeable and impermeable cracks in ferro-electric single crystals subjected to a mechanical load is investigated by using a phase field model.It is found that the electrical bound...Domain switching around electrically permeable and impermeable cracks in ferro-electric single crystals subjected to a mechanical load is investigated by using a phase field model.It is found that the electrical boundary conditions have little effect on the polarization distribution without any external load when the initial polarization is parallel to the crack,which is totally different from previous studies where the initial polarization is perpendicular to the crack.How-ever,the simulation results show that the electrical boundary conditions have great influence on the polarization distribution as well as the domain switching behavior when a mechanical load is applied.The critical mechanical load of domain switching with a permeable crack is much smaller than that in the case of an impermeable crack.展开更多
We prove the existence of global solutions to the initial-boundary-value problem on the half space R＋ for a one-dimensional viscous ideal polytropic gas. Some suitable assumptions are made to guarantee the existence ...We prove the existence of global solutions to the initial-boundary-value problem on the half space R＋ for a one-dimensional viscous ideal polytropic gas. Some suitable assumptions are made to guarantee the existence of smooth solutions. Employing the L2- energy estimate, we prove that the impermeable problem has a unique global solutionis.展开更多
This paper presents the results of an experimental study on the influences of floodplain impermeable groynes on flow structure, velocity, and water depth around the groyne（s）. A wooden symmetrical compound channel w...This paper presents the results of an experimental study on the influences of floodplain impermeable groynes on flow structure, velocity, and water depth around the groyne（s）. A wooden symmetrical compound channel was used. Groyne models with three different groyne relative lengths, 0.5, 0.75, and 1.0, were used on one floodplain with single and series arrangements. Analysis of the experimental results using the measured flow velocity and water depth values showed that flow structure, velocity, and water depth mainly depend on groyne relative length and the relative distance between series groynes. The flow velocity at the main channel centerline increased by about 40%, 60%, and 85%, and in other parts on the horizontal plane at the floodplain mid-water, depth by about 75%, 125%, and 175% of its original value in eases of one-side floodplain groyne（s） with relative lengths of 0.5, 0.75, and 1.0, respectively. The effective distance between two groynes in series arrangement ranges from 3 to 4 times the groyne length. Using an impermeable groyne with a large relative length in river floodplains increases the generation of eddy and roller zones downstream of the groyne, leading to more scouring and deposition. To avoid that, the groyne relative length must be kept below half the floodplain width,展开更多
Analytical solution is obtained for the pressure response of a slanted well in a slab reservoir with an impermeable fault. Based on the basic point source solution in an infinite space, the basic point source solution...Analytical solution is obtained for the pressure response of a slanted well in a slab reservoir with an impermeable fault. Based on the basic point source solution in an infinite space, the basic point source solution is obtained by using the mirror image principle. Wellbore pressure response of a slanted well is obtained by integration of the basic point source solution along the trajectory of a slanted well and the type curves are computed. The dimensionless bottom hole pressure and type curves are obtained and the sensitivities of related parameters are discussed. The model presented in this paper could be used for the well test analysis of a slanted well in a reservoir bounded by an impermeable fault.展开更多
This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume me...This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume method(FVM) and volume of fluid(VOF) method are adopted to simulate the flow field around the pipeline.The pressure distribution along the sandy bed surface is obtained by considering the variation of water surface.Furthermore,the effects of water depth,unidirectional and bidirectional impermeable plates on pressure difference are discussed.The seepage flow field of sandy bed near underwater pipeline is numerically simulated using the laminar and porous media model.On this basis,the effect of the impermeable plate length on hydraulic gradient is investigated and the critical length of impermeable plate is obtained.The simulated results show that when the water depth is smaller than 5.00D(D is the diameter of pipeline),the effect of the water depth on the pressure difference is remarkable.The pressure differences between two endpoints of both the unidirectional and bidirectional plates decrease with the increase of the plate length.The variations of the pressure differences for both the unidirectional and bidirectional plates are similar.With the increase of plate length,the hydraulic gradient decreases and the piping at the seepage exit is avoided effectively as long as it reaches a certain length.Such a critical length of the plate decreases with the increase of the water depth.When water depth is larger than 4.00D,the effect of the water depth on the critical length is small.For the same water depth,the critical length of impermeable plate increases with the increase of the dimensionless flow parameter.Numerical simulation results are in good agreement with the available experimental measurements.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos: 50174011 10172028) the Science Tech. Research Program of Heilongjiang Provincial Education Department (Grant No: 10531032).
文摘The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the solution of model is expanded into a series in powers of perturbation parameter. By using the Boundary Element Method (BEM) and Duhamel principle, wellbore pressure with effects of skins and wellbore storage is obtained. The type curves are plotted and analyzed considering effects of heterogeneity, arbitrary shape and impermeable barriers. Finally, the results obtained by perturbation boundary element method is compared with the analytical solution and is available for the transient pressure analysis of arbitrary shaped reservoirs.
基金supported by the Eco-environmental Monitoring Network of the Three Gorges Project, Three Gorges Project Construction Committee of the State Council, Chinathe National Natural Science Foundation of China (Nos. 40871147 and 30870410)
文摘The increased application of chemical fertilizers in citrus orchards and the non-point source nitrogen(N) and phosphorus(P)diffusion threaten the fresh water quality of the Three Gorges Reservoir area of China. A 10-year field trial on sloping citrus lands was conducted to evaluate five protection methods for reducing N and P losses: 1) intercropping with perennial white clover(CW); 2) straw mulching of the soil surface(CS); 3) intercropping with yellow daylily contour hedgerows(CH); 4) an impermeable membrane buried in the soil along the contour lines(CM); and 5) intercropping with a rotation of wheat and peanut(CWP). An area of conventional citrus management was also maintained as the control(CK). The results showed that CM and CH were the most effective methods for reducing surface runoff. The sediment yield were reduced at the highest rate by CW and CH and was also significantly reduced by CS. Reduced runoff volume and sediment yield were the crucial mechanism for the reductions in N and P losses. Compared with the control, CW, CS, CH, and CM reduced annual runoff by 9%, 13%, 25%, and 30%, sediment yield by 77%, 55%, 71%, and 28%,N loss by 10%, 23% 36%, and 37%, and P loss by 39%, 31%, 27%, and 25%, respectively. CW, CS, CH, and CM were effective in reducing N and P losses from the sloping citrus land. However, over the long-term, surface soil nutrient accumulation in CW, CS, and CH diminished the benefit of those methods in reducing N and P losses. In addition, CWP increased soil erosion and nutrient loss,which showed that citrus intercropping with other crops was an unsuitable method for citrus sloping land in the Three Gorges area.
文摘The Urban Commune of Maradi in Niger experienced increasingly frequent flooding following rainy episodes generating volumes and water flows that are difficult to control in recent years. This study aims to determine the impacts of runoff water in Commune II of Maradi City and to assess the role of urban planning in runoff management, as well as the strengths and weaknesses of urban sanitation in Maradi. The methodological approach used consisted of: 1) an interpretation of documentary data, 2) gathering information on runoff at several sites in the study area, and 3) interviews and questionnaires with local communities. This approach made it possible to understand the degree of vulnerability of the populations to flooding and then to propose sustainable solutions to reduce the vulnerability of the affected populations, through the implementation of effective urban rainwater management practices (USWMP). The results show that the impacts of runoff are mainly related to the lack of adequate storm water drainage networks in the area, but also to the nature of the habitats. Geomorphological factors such as the nature of the soil, the slope of the terrain and the altitude increase the degree of risk. In addition, the inadequacy and dilapidation of the drainage systems of the canals and above all the anarchic occupation of the land linked to accelerated urbanization are the cause of flooding by stagnation of rainwater. A phenomenon now linked to numerous deteriorations of urban equipment, the runoff of rainwater in the city of Maradi carries so many pollutants that municipalities, businesses and individuals should put in place pollution prevention measures.
基金Project supported by the 973 of China (Grant No: 2005cb221304), the National Natural Science Foundation of China(Grant No: 50174011)
文摘The steady-state flow mathematical model of arbitrary shaped homogeneous reservoirs with impermeable barrier is constructed in this paper. By using Boundary Element Method （BEM）, the mathematical model is solved. And a streamline generating technique is presented. The figures of streamlines are plotted and analyzed considering the effect of complex boundary and impermeable barriers. Through analyzing it indicates that the size, shape and orientation of impermeable barriers have various degree of influence on the streamlines. So, if there are impermeable barriers in reservoir according to the geological materials, the influence of impermeable barriers must be considered when adjusting flood pattern and injection strategy.
基金Funded by Natural Science Foundation of Hubei Province (No.2000J027)
文摘A kind of high impermeable and crack-resistance chemical admixture ( HICRCA) was prepared , which is a compound chemical admixture composed of an expansion ingredient, density ingredient, and organic hydrophobic poreblocking ingredient. The results of the experiments indicate that the addition of HICRCA improves mortar and concrete in the following performances: (1) perfect workability: slump is more than 22cm, theslump afar 3h is about 16cm; (2) high impermeability:for the mortar, the pervious height under a water pressure of 1.5MPa is 1.5cm,for the concrete, the pervious height under a water pressure of 5.0MPa is 2. 2cm;(3) high crack-resistance: there is a micro-expansion at the age of 90d; (4) high compressivestrength: compared with the controlled concrete, the compressive strengths at the age of 3d and 2Sd are improved by 66.4% and 62.0% , respectively. At the same time, the effects of different curing condition on mortar and concrete expansive andshrinkage performance were studied. In addition, the impermeable and crack-resistance mechanism, was investigatedin the present paper.
基金This work is supported by the Research Grants Council(RGC)of Hong Kong(No.15226322)the National Natu‐ral Science Foundation of China(No.42207210).
文摘Suffusion in broadly graded granular soils is caused by fluid flow and is a typical cause of geo-hazards.Previous studies of it have mainly focused on suffusion in homogeneous soil specimens.In this study,the coupled discrete element method(DEM)and computational fluid dynamics(CFD)approach is adopted to model suffusion in multi-layered soils with different fines contents,and soils with one or more impermeable zones.The parameters of the CFD-DEM model are first calibrated with the classic Ergun test and a good match with experiment is obtained.Then suffusion in multi-layered soils with different fines contents and impermeable zones is simulated and discussed.The simulation results show that,for soils with multiple layers,the cumulative eroded mass is mainly determined by the fines content of the bottom layer.In general,the higher the fines content of the bottom soil layer,the higher the cumulative eroded mass.In addition,suffusion is more severe if the fines content of the layer above is decreased.Impermeable zones inside soil specimens can increase the flow velocity around those zones,facilitating the migration of fine particles and intensifying suffusion.
基金supported by the National Natural Science Foundation of China (Nos. 10832009,11002123 and 11090333)the Zhejiang Provincial Natural Science Foundation under grant R6110115+1 种基金the Chinese Universities Scientific Fund under grant 2009QNA4035the program of Key Team of Technological Innovation of Zhejiang Province under grant2011R09025-07
文摘Domain switching around electrically permeable and impermeable cracks in ferro-electric single crystals subjected to a mechanical load is investigated by using a phase field model.It is found that the electrical boundary conditions have little effect on the polarization distribution without any external load when the initial polarization is parallel to the crack,which is totally different from previous studies where the initial polarization is perpendicular to the crack.How-ever,the simulation results show that the electrical boundary conditions have great influence on the polarization distribution as well as the domain switching behavior when a mechanical load is applied.The critical mechanical load of domain switching with a permeable crack is much smaller than that in the case of an impermeable crack.
文摘We prove the existence of global solutions to the initial-boundary-value problem on the half space R＋ for a one-dimensional viscous ideal polytropic gas. Some suitable assumptions are made to guarantee the existence of smooth solutions. Employing the L2- energy estimate, we prove that the impermeable problem has a unique global solutionis.
文摘This paper presents the results of an experimental study on the influences of floodplain impermeable groynes on flow structure, velocity, and water depth around the groyne（s）. A wooden symmetrical compound channel was used. Groyne models with three different groyne relative lengths, 0.5, 0.75, and 1.0, were used on one floodplain with single and series arrangements. Analysis of the experimental results using the measured flow velocity and water depth values showed that flow structure, velocity, and water depth mainly depend on groyne relative length and the relative distance between series groynes. The flow velocity at the main channel centerline increased by about 40%, 60%, and 85%, and in other parts on the horizontal plane at the floodplain mid-water, depth by about 75%, 125%, and 175% of its original value in eases of one-side floodplain groyne（s） with relative lengths of 0.5, 0.75, and 1.0, respectively. The effective distance between two groynes in series arrangement ranges from 3 to 4 times the groyne length. Using an impermeable groyne with a large relative length in river floodplains increases the generation of eddy and roller zones downstream of the groyne, leading to more scouring and deposition. To avoid that, the groyne relative length must be kept below half the floodplain width,
文摘Analytical solution is obtained for the pressure response of a slanted well in a slab reservoir with an impermeable fault. Based on the basic point source solution in an infinite space, the basic point source solution is obtained by using the mirror image principle. Wellbore pressure response of a slanted well is obtained by integration of the basic point source solution along the trajectory of a slanted well and the type curves are computed. The dimensionless bottom hole pressure and type curves are obtained and the sensitivities of related parameters are discussed. The model presented in this paper could be used for the well test analysis of a slanted well in a reservoir bounded by an impermeable fault.
基金supported by the National Natural Science Foundation of China(Grant No.51279189)the National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2008AA09Z309)China Scholarship Council and University of Aberdeen
文摘This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume method(FVM) and volume of fluid(VOF) method are adopted to simulate the flow field around the pipeline.The pressure distribution along the sandy bed surface is obtained by considering the variation of water surface.Furthermore,the effects of water depth,unidirectional and bidirectional impermeable plates on pressure difference are discussed.The seepage flow field of sandy bed near underwater pipeline is numerically simulated using the laminar and porous media model.On this basis,the effect of the impermeable plate length on hydraulic gradient is investigated and the critical length of impermeable plate is obtained.The simulated results show that when the water depth is smaller than 5.00D(D is the diameter of pipeline),the effect of the water depth on the pressure difference is remarkable.The pressure differences between two endpoints of both the unidirectional and bidirectional plates decrease with the increase of the plate length.The variations of the pressure differences for both the unidirectional and bidirectional plates are similar.With the increase of plate length,the hydraulic gradient decreases and the piping at the seepage exit is avoided effectively as long as it reaches a certain length.Such a critical length of the plate decreases with the increase of the water depth.When water depth is larger than 4.00D,the effect of the water depth on the critical length is small.For the same water depth,the critical length of impermeable plate increases with the increase of the dimensionless flow parameter.Numerical simulation results are in good agreement with the available experimental measurements.
