Due to large topography slopes in natural rivers, pollutant concentration embodies a property of three-dimensional distribution when wastewater is discharged from effluents along the bank. With the sigma coordinate al...Due to large topography slopes in natural rivers, pollutant concentration embodies a property of three-dimensional distribution when wastewater is discharged from effluents along the bank. With the sigma coordinate along the vertical dimension fitted to both the moving free surface and the bed topography, a three-dimensional numerical model was developed in the present work to address pollutant transport processes in the above-mentioned cases. To avoid the reduction in accuracy caused by spurious diffusion in the case of steep bottom slopes, a formula for horizontal diffusion in the sigma coordinate system was derived. A case study for the side discharge into a straight open-channel flow shows that numerical results are verified well by experimental data. Furthermore, the present model is also verified by the simulation of discharging wastewater from Fuling Phosphorus Factory effluent into the Three Gorges Reservoir and the agreement between the numerical simulation results and field observation data is satisfactory. The change of the mixing zone scope in the water surface versus the layers along the vertical dimension was also discussed in detail. The study shows that a more realistic calculation for pollutant discharge has been provided by the present model than by the depth-average model which predicts an unrealistically smaller mixing zone.展开更多
A numerical model of transverse mixing in natural rivers has been presented by using the body-fitted coordinate systems,which is capable of describing the complex flow and mixing characteristics of rivers.To study the...A numerical model of transverse mixing in natural rivers has been presented by using the body-fitted coordinate systems,which is capable of describing the complex flow and mixing characteristics of rivers.To study the validity and to illustrate the applicability of this model,field measurement date in the Gan River near Nanchang have been used to compare the numerical results.展开更多
While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponen...While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponents such as 1/6 and 1/7 are generally applied. However, exponent of power law is an index representing bed resistance related with relative roughness and furthermore influences the shapes of vertical velocity distribution. The purpose of this study is to investigate characteristics of vertical velocity distribution of the natural rivers by testing and optimizing previous methods used for determination of power law exponent with vertical velocity distribution data collected with ADCPs during the years of 2005 to 2009 from rivers in South Korea. Roughness coefficient has been calculated from the equation of Limerinos. And using theoretical and empirical formulae, and representing relationships between bed resistance and power law exponent, it has been evaluated whether the exponents suggested by these equations appropriately reproduce vertical velocity distribution of actual rivers. As a result, it has been confirmed that there is an increasing trend of power law exponent as bed resistance increases. Therefore, in order to correctly predict vertical velocity distribution in the natural rivers, it is necessary to use an exponent that reflects flow conditions at the field.展开更多
This paper is concerned with the experiments of simulating self-purification of heavy metal pollutants in natural rivers, such as tributaries polluted by heavy metal polutants joining a main stream, or an uncontaminat...This paper is concerned with the experiments of simulating self-purification of heavy metal pollutants in natural rivers, such as tributaries polluted by heavy metal polutants joining a main stream, or an uncontaminated tributary with much sediment entering a main stream polluted by heavy metal pollutants, and the experiments on the effect of sediment movement on the adsorption of heavy metal pollutants. Further-more, the effect of turbulence, sediment supply conditions and sediment motion patterns on the adsorption of heavy metal pollutants are studied in a device, in which turbulence is generated by a harmonically vibrating set of grids. The results indicate that sediment motion pattern has no effect on the characteristic parameters in the adsorption isotherm, such as the saturated adsorption content by unit weight of seidment and the constant of adsorption-desorption rate in the Langmuir adsorption isotherm, but it has significant effect on the coefficient of adsorption rate (or the coefficient of desorption rate). When the turbulent intensity of flow is low and all sediment exists as bottom mud, the coefficient of adsorption rate of sediment (or the coefficient of desorption rate of sediment) is very small, thus descending rate of concentration of dissolved heavy metal pollutant concentration is small, and when the turbulent intensity of flow is high, sediment supply condition, that is, whether sediment exists on the bed or not, influences greatly the variation of dissolved heavy metal pollutant concentration. When the sediment on the bed could be lifted up, descending rate of dissolved heavy metal pollutant concentration is large. In other wards, the coefficient of adsorption rate (or the coefficient of desorption rate) by unit weight of suspended sediment is much larger than that by unit weight of bottom mud.展开更多
From 2009 until 2012 the project“Watershed Management of Forest Land in Beijing,Restoration of Small Water Bodies(SWBR)”was implemented,combining Close to Nature Forest Management and Restoration of Small Water Bodi...From 2009 until 2012 the project“Watershed Management of Forest Land in Beijing,Restoration of Small Water Bodies(SWBR)”was implemented,combining Close to Nature Forest Management and Restoration of Small Water Bodies.The targets were to improve flood control,to enhance the ecological conditions by copying nature and to support the recreational value of small water bodies,all in cooperation with people living there.The efficiency of each project was proofed by comparison of biological and hydro-morphological assessment before the projects started and 2-3 years after they were finished.The results confirmed the ecological improvements of the restored river sections and showed the achievements.Guidelines to assess the biological and hydro-morphological status of rivers were developed and there are plans to introduce them as Beijing Standards.Planning and implementation of measures,based on experiences in Central Europe,will be documented in a handbook.&2015 International Research and Training Center on Erosion and Sedimentation and China Water and Power Press.Production and Hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).展开更多
基金supported by the National Basic Research and Development Program of China (973 Program, Grant No. 2006CB403304)
文摘Due to large topography slopes in natural rivers, pollutant concentration embodies a property of three-dimensional distribution when wastewater is discharged from effluents along the bank. With the sigma coordinate along the vertical dimension fitted to both the moving free surface and the bed topography, a three-dimensional numerical model was developed in the present work to address pollutant transport processes in the above-mentioned cases. To avoid the reduction in accuracy caused by spurious diffusion in the case of steep bottom slopes, a formula for horizontal diffusion in the sigma coordinate system was derived. A case study for the side discharge into a straight open-channel flow shows that numerical results are verified well by experimental data. Furthermore, the present model is also verified by the simulation of discharging wastewater from Fuling Phosphorus Factory effluent into the Three Gorges Reservoir and the agreement between the numerical simulation results and field observation data is satisfactory. The change of the mixing zone scope in the water surface versus the layers along the vertical dimension was also discussed in detail. The study shows that a more realistic calculation for pollutant discharge has been provided by the present model than by the depth-average model which predicts an unrealistically smaller mixing zone.
文摘A numerical model of transverse mixing in natural rivers has been presented by using the body-fitted coordinate systems,which is capable of describing the complex flow and mixing characteristics of rivers.To study the validity and to illustrate the applicability of this model,field measurement date in the Gan River near Nanchang have been used to compare the numerical results.
文摘While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponents such as 1/6 and 1/7 are generally applied. However, exponent of power law is an index representing bed resistance related with relative roughness and furthermore influences the shapes of vertical velocity distribution. The purpose of this study is to investigate characteristics of vertical velocity distribution of the natural rivers by testing and optimizing previous methods used for determination of power law exponent with vertical velocity distribution data collected with ADCPs during the years of 2005 to 2009 from rivers in South Korea. Roughness coefficient has been calculated from the equation of Limerinos. And using theoretical and empirical formulae, and representing relationships between bed resistance and power law exponent, it has been evaluated whether the exponents suggested by these equations appropriately reproduce vertical velocity distribution of actual rivers. As a result, it has been confirmed that there is an increasing trend of power law exponent as bed resistance increases. Therefore, in order to correctly predict vertical velocity distribution in the natural rivers, it is necessary to use an exponent that reflects flow conditions at the field.
文摘This paper is concerned with the experiments of simulating self-purification of heavy metal pollutants in natural rivers, such as tributaries polluted by heavy metal polutants joining a main stream, or an uncontaminated tributary with much sediment entering a main stream polluted by heavy metal pollutants, and the experiments on the effect of sediment movement on the adsorption of heavy metal pollutants. Further-more, the effect of turbulence, sediment supply conditions and sediment motion patterns on the adsorption of heavy metal pollutants are studied in a device, in which turbulence is generated by a harmonically vibrating set of grids. The results indicate that sediment motion pattern has no effect on the characteristic parameters in the adsorption isotherm, such as the saturated adsorption content by unit weight of seidment and the constant of adsorption-desorption rate in the Langmuir adsorption isotherm, but it has significant effect on the coefficient of adsorption rate (or the coefficient of desorption rate). When the turbulent intensity of flow is low and all sediment exists as bottom mud, the coefficient of adsorption rate of sediment (or the coefficient of desorption rate of sediment) is very small, thus descending rate of concentration of dissolved heavy metal pollutant concentration is small, and when the turbulent intensity of flow is high, sediment supply condition, that is, whether sediment exists on the bed or not, influences greatly the variation of dissolved heavy metal pollutant concentration. When the sediment on the bed could be lifted up, descending rate of dissolved heavy metal pollutant concentration is large. In other wards, the coefficient of adsorption rate (or the coefficient of desorption rate) by unit weight of suspended sediment is much larger than that by unit weight of bottom mud.
文摘From 2009 until 2012 the project“Watershed Management of Forest Land in Beijing,Restoration of Small Water Bodies(SWBR)”was implemented,combining Close to Nature Forest Management and Restoration of Small Water Bodies.The targets were to improve flood control,to enhance the ecological conditions by copying nature and to support the recreational value of small water bodies,all in cooperation with people living there.The efficiency of each project was proofed by comparison of biological and hydro-morphological assessment before the projects started and 2-3 years after they were finished.The results confirmed the ecological improvements of the restored river sections and showed the achievements.Guidelines to assess the biological and hydro-morphological status of rivers were developed and there are plans to introduce them as Beijing Standards.Planning and implementation of measures,based on experiences in Central Europe,will be documented in a handbook.&2015 International Research and Training Center on Erosion and Sedimentation and China Water and Power Press.Production and Hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).
