This paper presents a review on previous activities of mining on water resources around active and abandoned mines/quarries across Ebonyi State,South-Eastern,Nigeria.As high demand for water increases due to populatio...This paper presents a review on previous activities of mining on water resources around active and abandoned mines/quarries across Ebonyi State,South-Eastern,Nigeria.As high demand for water increases due to population growth and rapid development across the state,it is of upmost importance to periodically review water quality and also monitor water resources.However,less information is available on evaluation of impact on mining activities on water resources.For the purpose of this research,related articles were downloaded from Google,published article on effect of mining on water resources was download and thoroughly studied to evaluate effect of mining on water resources of the study area.Findings revealed that past mining activities has lead to chains of complex chemical reactions that has altered the quality of water resources.展开更多
In the present study,the flow over the stepped spillway was numerically investigated by using Flow3D model.The effect of step angle on different properties of Nappe flow regime such as the water surface profile,locati...In the present study,the flow over the stepped spillway was numerically investigated by using Flow3D model.The effect of step angle on different properties of Nappe flow regime such as the water surface profile,location of free-surface aeration inception,Froude number at the spillway’s toe,and pressure,flow velocity,air concentration and cavitation index were evaluated.The realizable k–εwas applied as the turbulence model,and Volume of Fluid(VOF)model was used to determine the free surface flow profiles of the spillway.The model was verified using experimental data.In order to investigate the different characteristics of Nappe flow regime,17 numerical runs was designed,in which,four step angles,four flow discharge were considered to investigate the flow characteristics over the stepped spillway.The results indicated that the numerical model is well suited with the experimental data over the stepped spillway(RMSE=0.147 and ARE=6.9%).In addition,with increasing the step angles,the aeration inception point is generally moved downstream.By increasing the step angles from zero to 10 degrees,the Froude number does not change significantly,however,at the angle of 15 degrees,the Froude number decreases by about 42 percent.展开更多
Spur dykes also known as Groynes are often used to either divert or attract the flow from the main structure to safeguard their life.Those structures may be bridge piers,abutments or any similar hydraulics structures....Spur dykes also known as Groynes are often used to either divert or attract the flow from the main structure to safeguard their life.Those structures may be bridge piers,abutments or any similar hydraulics structures.Spur dykes are also used to save the cutting of banks on concave side of stream.Lots of work have been done in recent past on spur dykes by many investigators in which various hydraulic and geometrical parameters of spur dykes such as discharge,sediment size,flow velocity,shear stress,spur dykes shape,size and submergence etc.are studied in detail.But mostly all the studies were pointed out in straight open channels.Very few studies were done in curved channel and only their similar effects were studied.In present thesis main emphasis is given to study the effect of orientation and location of spur dykes in meandering channel on the bed of downstream side.In the present study experimental work has been carried out in 80°bend and constant discharge(Q=4.5 l/s)is allowed to pass in channel without spur dyke.It is found that maximum scouring occurs at angular displacementθ=60°to 80°in the vicinity of outer bank.To minimize this scouring,spur dyke has been installed at angular displacementθ=20°,40°&60°by changing the dyke angleα=60°,90°&120°respectively.It is found that scouring atθ=60°is reduced by installing spur dyke at angular displacementθ=40°which is oriented atα=60°and scouring atθ=80°is reduced by installing spur dyke at angular displacementθ=60°which is oriented atα=60°.展开更多
Offshore Horizontal Axis Wind Turbines(HAWT)are used globally as a source of clean and renewable energy.Turbine efficiency can be improved by optimizing the geometry of the turbine blades.Turbines are generally design...Offshore Horizontal Axis Wind Turbines(HAWT)are used globally as a source of clean and renewable energy.Turbine efficiency can be improved by optimizing the geometry of the turbine blades.Turbines are generally designed in a way that its orientation is adjustable to ensure the wind direction is aligned with the axis of the turbine shaft.The deflection angle from this position is defined as yaw angle of the turbine.Understanding the effects of the yaw angle on the wind turbine performance is important for the turbine safety and performance analysis.In this study,performance of a yawed HAWT is studied by computational fluid dynamics.The wind flow around the turbine is simulated by solving the Reynolds-Averaged Navier-Stokes equations using software ANSYS Fluent.The principal aim of this study is to quantify the yaw angle on the efficiency of the turbine and to check the accuracy of existing empirical formula.A three-bladed 100-m diameter prototype HAWT was analysed through comprehensive Computational Fluid Dynamics(CFD)simulations.The turbine efficiency reaches its maximum value of 33.9%at 0°yaw angle and decreases with the increase of yaw angle.It was proved that the cosine law can estimate the turbine efficiency with a yaw angle with an error less 10%when the yaw angle is between-30°and 30°.The relative error of the cosine law increase at larger yaw angles because of the power is reduced significantly.展开更多
Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge p...Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge piers and foundations.Several investigators have extensively studied local scour around isolated bridge pier,but modern designs of the bridges comprise of wide span and thus group of piers rather than a single pier.The flow and scour pattern around group of piers are different from the case of a single pier due to the interaction effect.The objective of present study is to investigate the effect of mutual interference of bridge piers on local scour experimentally around two piers in non-cohesive bed.Experiments were carried out on model bridge piers of circular cross section in a meandering channel.It was observed that when front and rear piers were placed at an angular displacement ofθ=40°and 80°respectively,maximum depth of scour is maximum.Hereθis the angle the line drawn at the inlet of bend to the line joining the centre of curvature and any point on the outer portion of the bend.展开更多
Change silt charge of water in the rivers can negatively be reflected in throughput the rivers beds,stability of coast,change of river structures,disappearance of boggy places,etc.In work questions of variabilit...Change silt charge of water in the rivers can negatively be reflected in throughput the rivers beds,stability of coast,change of river structures,disappearance of boggy places,etc.In work questions of variability silt charge waters in the river Sluch in time and on length of the river are considered.It is revealed that in time average and maximal silt charge waters decrease.While on length of the river change silt charge waters is shown not precisely,similar on some increase silt charge waters to a mouth of the river.The researches led by the factorial analysis and graphic-analytical method on the basis of long-term materials of measurement of charges of water have shown that,on a part of posts average depth of water in the river grows,and on others-cyclically changes with the general tendency to reduction.Average speed in them,accordingly,falls and grows.Stratification of interrelations of a silt charge with other factors on years is observed.The reasons of reduction of a silt charge are:1)agrarian and forest meliorative actions on a catchments of the river,hydraulic engineering construction;2)grassy bed of the river;3)change of a climate that promotes growth of temperature of a surface of soils and grassy bed of the river.In developed natural-climatic conditions expediently application on reservoirs of the antierosion organization of territory of the land tenure including agrarian-forests-meliorative actions that will allow to adjust outflow of a moisture from reservoirs to lower warming up of a surface of the soils,to provide against a high water protection and it will favorably be reflected in manufacture of agricultural production.展开更多
Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive materials.In this study,flat sheet PVDF membranes were synthe...Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive materials.In this study,flat sheet PVDF membranes were synthesized using phase inversion and water as the pore former.Remarkably,the water added in the casting solution improved the membrane pore sizes;where the maximum pore size was 0.58μm.Also,the incorporation of f-SiO2NPs in the membrane matrix considerably enhanced the membrane hydrophobicity.Specifically,the membrane contact angles increased from 96°to 153°.Additionally,other parameters investigated were mechanical strength and liquid entry pressure(LEP).The maximum recorded values were 2.26 MPa and 239 kPa,respectively.The modified membranes(i.e.,using water as the pore former and f-SiO2NPs)were the most efficient,showing maximum salt rejection of 99.9%and water flux of 11.6 LMH;thus,indicating their capability to be used as efficient materials for the recovery of high purity water in MD.展开更多
In the last decade,the construction of communication routes has intensified globally.As a result,many case studies have emerged related to the presence of saturated clayey soils in the foundation ground.In order to sp...In the last decade,the construction of communication routes has intensified globally.As a result,many case studies have emerged related to the presence of saturated clayey soils in the foundation ground.In order to speed up the execution of highways and railways in a safely manner,the designers use different methods for improving soft clays in terms of compressibility.The present paper aims to evaluate the efficiency of an electrochemical method used for the dewatering of a soft montmorillonite clay subgrade.The effects on the consolidation process are analyzed for the final conclusions.The advantages of the method are briefly discussed,and some potential areas for scientific research are proposed.展开更多
Aim of the study was to assess the physicochemical characteristics of rainwater at urban and rural(north B)Unguja.Twenty four(24)rainwater samples were analyzed for pH,electrical conductivity(EC)and total dissolved so...Aim of the study was to assess the physicochemical characteristics of rainwater at urban and rural(north B)Unguja.Twenty four(24)rainwater samples were analyzed for pH,electrical conductivity(EC)and total dissolved solids(TDS)and cations:calcium(Ca^2+),copper(Cu^2+),iron(Fe^2+),chromium(Cr VI),and anions:fluoride(F^-),nitrite and sulfate(SO4^2-).The investigated physicochemical parameters in the rainwater samples were within the permissible limits of the World Health Organization(WHO)drinking water quality guidelines.The ranges of concentration for the physical parameters analyzed were;pH:(5.8-7.7),EC:(5.08-35.6μS/cm),TDS:(1.68-20.16 mg/L,Ca:(0.163-24.331 mg/L),Cr:(VI):(BDL-0.029 mg/L),Cu:(BDL-0.085 mg/L);Fe:(BDL-0.068),anions were SO4^2-:(BDL-5.00 mg/L)and F^-:(BDL-0.5 mg/L).Nevertheless,there was no significant difference for the measured parameters between urban and rural areas.This is a good indication that the air quality in Zanzibar is remarkably not polluted with respect to the parameters studied.展开更多
This study investigated coal-mine drainage(AMD)and municipal wastewater(MWW)contaminant concentrations and conducted the combined treatment in phases I and II:phase I,evaluating the effects of mixing the two based on ...This study investigated coal-mine drainage(AMD)and municipal wastewater(MWW)contaminant concentrations and conducted the combined treatment in phases I and II:phase I,evaluating the effects of mixing the two based on the extent of acid neutralization and metals removal;phase II:conducting anaerobic batch reactor treatment of AMD and MWW under varying COD/sulfate ratios(0.04-5.0).In phase I,acid mine drainage water quality conditions are as follows:pH 4.5,acidity 467.5 mg/L as CaCO3,alkalinity 96.0 mg/L as CaCO3,Cl-11.8 mg/L,SO42-1722 mg/L,TDS 2757.5 mg/L,TSS 9.8 mg/L,BOD 14.7 mg/L,Fe 138.1 mg/L,Mg 110.8 mg/L.Mn 7.5 mg/L,Al 8.1 mg/L,Na 114.2 mg/L,and Ca 233.5 mg/L.Results of the mixing experiments indicated significant removal of selected metals(Fe 85~98%,Mg 0~65%,Mn 63~89%,Al 98~99%,Na 0~30%),acidity(77~95%)from the mine water and pH was raised to above 6.3.The Phase II results suggested under the wide range of COD/sulfate ratios,COD and sulfate removal varied from 37.4%-100%and 0%-93.5%respectively.During biological treatment,alkalinity was generated which leads to pH increase to around 7.6-8.5.The results suggested feasibility of the proposed technology for co-treatment of AMD and MWW.A conceptual design of co-treatment system which is expected to remove a matrix of pollutants has been provided to utilize all the locally available water resources to achieve the optimum treatment efficiency.The technology also offers an opportunity to significantly reduce capital and operating costs compared to the existing treatment methodologies used.Featured Application:In this study,we have measured the concentrations of contaminants in acid mine drainage(AMD)and municipal wastewater(MWW)and conducted the combined treatment in phases I and II.This is significant because in previous years there was a massive fish kill that is linked to the high total dissolved solids(TDS)and salinity content in the water.With the current proposed combined treatment technology,it shows high potential in reducing TDS and salinity content in the展开更多
Vortex-induced vibration(VIV)of multiple circular cylinders elastically connected together in a side-by-side arrangement subject to steady flow is investigated numerically at a low Reynolds number of 150 and a mass ra...Vortex-induced vibration(VIV)of multiple circular cylinders elastically connected together in a side-by-side arrangement subject to steady flow is investigated numerically at a low Reynolds number of 150 and a mass ratio of 2.Simulations are conducted for two-,five-and ten-cylinder systems over a wide range of reduced velocities.The aim of the study is to identify the high-amplitude response range of the reduced velocity for the multiple degree of freedom vibration system and identify the difference between the responses of the single-and multiple-degree-of-freedom vibrations.Unlike the single cylinder case,distinct lock-in between the response frequency and any of the structural natural frequencies in a wide range of reduced velocity is not observed in the multiple-cylinder cases.Instead,the response frequency increases continuously with increasing reduced velocity.High response amplitudes are found when the response frequency is between the first and the highest modal frequencies.In a multiple-cylinder system,the single-mode response,where the vibration is dominated by one mode,can be only found in low reduced velocity range.In the single-mode branch,the dominance of a single mode shape in the response can be clearly identified except at the boundary reduced velocity between two modes.The maximum response amplitude occurs in the multiple-mode response and interaction between the vortices in the wake of the cylinders is strong when the response amplitudes are high.展开更多
Climate change can alter the status quo of the world as we know today.Water resources may also be influenced by these plausible impacts.The common perception is that these changes may exacerbate the situation of water...Climate change can alter the status quo of the world as we know today.Water resources may also be influenced by these plausible impacts.The common perception is that these changes may exacerbate the situation of water resources in arid and semi-arid regions,such as the Middle-East,which are experiencing mild to severe water stress due to limited water availability and growing water demands.In that spirit,this study aims to investigate the possible impacts of climate change on surface water in Maharlou Lake basin,Iran.Reportedly,this basin has already shown some symptoms of the water-related crisis,which highlights the importance of conducting climate change studies in this region.The CansESM2 model was employed to predict the basin’s climatic response under various climate change scenarios.The hydrologic response of the basin was,then,simulated using IHACRES.The results have demonstrated a 4%decrease in average annual rainfall,a 2%increase in average annual temperature,and,finally,a 24%decrease in average annual streamflow of the basin in the(2010-2099)time window.While the results suggest that recent water-related challenges in the basin might have caused by climate change,further in-depth studies are required to reveal the exact reasons.展开更多
Pre-stressed structure and its application for civil engineering.Specificity of external loads of ships.Corresponded specificity of controllable pre-stressing.An example of pre-stressed structure and an decreasing est...Pre-stressed structure and its application for civil engineering.Specificity of external loads of ships.Corresponded specificity of controllable pre-stressing.An example of pre-stressed structure and an decreasing estimation of its mass(about 10%of the full displacement).Possibility of wider application.展开更多
A three dimensional model to predict the hydro-mechanical state of unsaturated and deformable material during hot air drying has been proposed.The material viscoelastic behaviour was formulated using Bishop’s effecti...A three dimensional model to predict the hydro-mechanical state of unsaturated and deformable material during hot air drying has been proposed.The material viscoelastic behaviour was formulated using Bishop’s effective stress theory for partially saturated material using the liquid saturation as the Bishop parameter.The hydro-thermal and mechanical equations were coupled by the fluid pressure and the solid matter velocity.The model was applied to a deformable material(innovative clay-cellulose fibers composite)subjected to convective drying.A generalized Maxwell model with five elements,whose parameters were measured experimentally and correlated to water content was used to describe the material’s viscoelastic behavior.The hydro-thermal part of the proposed model was validated on the basis of a comparison of experimental and simulated drying rate curves.The Von Mises stress was simulated and compared to the experimental tensile strength in order to predict the time and the region of material failure.For a drying process at 95°C,the region of failure risk was identified.The failure may occur on the lateral surface of the slab in contact with air at a drying time of 2.5h.展开更多
The independent LNG(Liquified Nature Gas)containment is widely used for small or medium-sized LNG carrier and ship using LNG as fuels.The common tank pattern includes single-spherical-cylindrical tank and double-spher...The independent LNG(Liquified Nature Gas)containment is widely used for small or medium-sized LNG carrier and ship using LNG as fuels.The common tank pattern includes single-spherical-cylindrical tank and double-spherical-cylindrical tank,which is the key to design the hull structure and its support.The support is designed to connect the hull structure and LNG tank.Its main functions are heat transferring and force loading.This paper focus on the temperature field distribution of hull and its support structure.The thermal boundary conditions are simulated according to the heat transfer action,such as thermal convection,heat conduction and thermal radiation.The method on how to carry out thermal analysis is presented for an independent LNG containment.The case study is carried out with two typical independent LNG tanks.One is a tank with double spherical cylindrical in the LNG carrier,and the other is a tank with single spherical cylindrical on the deck of the ship using LNG as fuels.The result shows the method presented in this paper is a good reference for the structural design with independent LNG containment.展开更多
This document provides some guidelines to authors for submission in order to work towards a seamless submission process.While complete adherence to the following guidelines is not enforced,authors should note that fol...This document provides some guidelines to authors for submission in order to work towards a seamless submission process.While complete adherence to the following guidelines is not enforced,authors should note that following through with the guidelines will be helpful in expediting the copyediting and proofreading processes,and allow for improved readability during the review process.展开更多
This study is based on the hypothesis that the implementation of Integrated Water Resources Management(IWRM)tools in the Oueme watershed has not led to a systematic improvement in the degree of IWRM implementation in ...This study is based on the hypothesis that the implementation of Integrated Water Resources Management(IWRM)tools in the Oueme watershed has not led to a systematic improvement in the degree of IWRM implementation in the Oueme Valley in Benin.Methodologically,data were collected through a semi-structured survey of stakeholder families in the study area using snowball sampling.The tool used was the form developed by the United Nations to collect data to assess the level of IWRM implementation.The four(4)assessment criteria,each covering a key component of IWRM,are the enabling environment,institutions and participation,management tools and financing.The results obtained per criteria according to the stepwise methodology adopted reveal on average a degree of implementation of 40 on a scale of 0 to 100 in the Oueme basin.This value varies according to the geographical area and the factors considered.This study,which is a decision-making tool,provides a guide for governments to monitor the progress of integrated water resources management in their territory.展开更多
Ice Engineering is associated with how to solve challenges from different kinds of ice,such as,sea ice,river ice,lake ice,icing,and snow in cold regions.The aim is to design special structures which could resist struc...Ice Engineering is associated with how to solve challenges from different kinds of ice,such as,sea ice,river ice,lake ice,icing,and snow in cold regions.The aim is to design special structures which could resist structural and global impact from drifting ice and freezing ice.The foundation of ice engineering is to study ice properties and its action on various structures,icing process within ice mechanics by using theoretical analysis,numerical simulation,model scale tests and field measurements.Ice is a kind of non-uniform material and its properties depends on many factors such as loading rate,temperature,freezing disturbance.The scope of Ice Engineering covers the science and engineering projects in cold regions,especially for offshore oil and gas,Arctic shipping,and offshore renewable energy.展开更多
have been done in the past by many researchers.Many factors which affect scour around piers such as shape of piers,size,positioning and orientation etc.have been studied in detail by them.However,similar studies in me...have been done in the past by many researchers.Many factors which affect scour around piers such as shape of piers,size,positioning and orientation etc.have been studied in detail by them.However,similar studies in meandering channels are scanty.Very few researchers have studied the effect of angular displacement which has considerable effects of scour around bridge piers.In this paper an attempt has been made to carry out a detailed study of angular displacement on scour.A constant diameter bridge pier of circular shape has been tested in a meandering channel bend with bend angle as 800.The test bed was prepared by using uniform sand having d50 as 0.27 mm and run was taken for a discharge of 2.5 l/s.展开更多
Surface water samples were collected from selected locations along river Panchaganga,from Kolhapur to Narsobawadi during April 2019.Physicochemical parameters were determined in the laboratory and chemical mass balanc...Surface water samples were collected from selected locations along river Panchaganga,from Kolhapur to Narsobawadi during April 2019.Physicochemical parameters were determined in the laboratory and chemical mass balance approach was adopted to estimate the individual ionic loads in the river water.Streeter-Phelps equation was applied to derive a relationship between DO and BOD_(5).Model parameters such as De-oxygenation Rate(K_(d))and Re-aeration Rates(K_(r))were optimized using different empirical methods.The result of chemical mass balance showed an increase in the loading of various ions from upstream to downstream which could be attributed to agricultural and industrial wastes that enter the main stream.De-oxygenation rate and re-aeration constants were calculated using various empirical methods.DO sag curve was developed using Streeter Phelp’s model and compared with the observed parameters which showed a significant correlation.DO-BOD concentration observed along the course of the river indicated that the self-purification capacity of the river is high due to which the river regains the lost DO level at a distance less than 50 meters.展开更多
文摘This paper presents a review on previous activities of mining on water resources around active and abandoned mines/quarries across Ebonyi State,South-Eastern,Nigeria.As high demand for water increases due to population growth and rapid development across the state,it is of upmost importance to periodically review water quality and also monitor water resources.However,less information is available on evaluation of impact on mining activities on water resources.For the purpose of this research,related articles were downloaded from Google,published article on effect of mining on water resources was download and thoroughly studied to evaluate effect of mining on water resources of the study area.Findings revealed that past mining activities has lead to chains of complex chemical reactions that has altered the quality of water resources.
文摘In the present study,the flow over the stepped spillway was numerically investigated by using Flow3D model.The effect of step angle on different properties of Nappe flow regime such as the water surface profile,location of free-surface aeration inception,Froude number at the spillway’s toe,and pressure,flow velocity,air concentration and cavitation index were evaluated.The realizable k–εwas applied as the turbulence model,and Volume of Fluid(VOF)model was used to determine the free surface flow profiles of the spillway.The model was verified using experimental data.In order to investigate the different characteristics of Nappe flow regime,17 numerical runs was designed,in which,four step angles,four flow discharge were considered to investigate the flow characteristics over the stepped spillway.The results indicated that the numerical model is well suited with the experimental data over the stepped spillway(RMSE=0.147 and ARE=6.9%).In addition,with increasing the step angles,the aeration inception point is generally moved downstream.By increasing the step angles from zero to 10 degrees,the Froude number does not change significantly,however,at the angle of 15 degrees,the Froude number decreases by about 42 percent.
文摘Spur dykes also known as Groynes are often used to either divert or attract the flow from the main structure to safeguard their life.Those structures may be bridge piers,abutments or any similar hydraulics structures.Spur dykes are also used to save the cutting of banks on concave side of stream.Lots of work have been done in recent past on spur dykes by many investigators in which various hydraulic and geometrical parameters of spur dykes such as discharge,sediment size,flow velocity,shear stress,spur dykes shape,size and submergence etc.are studied in detail.But mostly all the studies were pointed out in straight open channels.Very few studies were done in curved channel and only their similar effects were studied.In present thesis main emphasis is given to study the effect of orientation and location of spur dykes in meandering channel on the bed of downstream side.In the present study experimental work has been carried out in 80°bend and constant discharge(Q=4.5 l/s)is allowed to pass in channel without spur dyke.It is found that maximum scouring occurs at angular displacementθ=60°to 80°in the vicinity of outer bank.To minimize this scouring,spur dyke has been installed at angular displacementθ=20°,40°&60°by changing the dyke angleα=60°,90°&120°respectively.It is found that scouring atθ=60°is reduced by installing spur dyke at angular displacementθ=40°which is oriented atα=60°and scouring atθ=80°is reduced by installing spur dyke at angular displacementθ=60°which is oriented atα=60°.
文摘Offshore Horizontal Axis Wind Turbines(HAWT)are used globally as a source of clean and renewable energy.Turbine efficiency can be improved by optimizing the geometry of the turbine blades.Turbines are generally designed in a way that its orientation is adjustable to ensure the wind direction is aligned with the axis of the turbine shaft.The deflection angle from this position is defined as yaw angle of the turbine.Understanding the effects of the yaw angle on the wind turbine performance is important for the turbine safety and performance analysis.In this study,performance of a yawed HAWT is studied by computational fluid dynamics.The wind flow around the turbine is simulated by solving the Reynolds-Averaged Navier-Stokes equations using software ANSYS Fluent.The principal aim of this study is to quantify the yaw angle on the efficiency of the turbine and to check the accuracy of existing empirical formula.A three-bladed 100-m diameter prototype HAWT was analysed through comprehensive Computational Fluid Dynamics(CFD)simulations.The turbine efficiency reaches its maximum value of 33.9%at 0°yaw angle and decreases with the increase of yaw angle.It was proved that the cosine law can estimate the turbine efficiency with a yaw angle with an error less 10%when the yaw angle is between-30°and 30°.The relative error of the cosine law increase at larger yaw angles because of the power is reduced significantly.
文摘Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge piers and foundations.Several investigators have extensively studied local scour around isolated bridge pier,but modern designs of the bridges comprise of wide span and thus group of piers rather than a single pier.The flow and scour pattern around group of piers are different from the case of a single pier due to the interaction effect.The objective of present study is to investigate the effect of mutual interference of bridge piers on local scour experimentally around two piers in non-cohesive bed.Experiments were carried out on model bridge piers of circular cross section in a meandering channel.It was observed that when front and rear piers were placed at an angular displacement ofθ=40°and 80°respectively,maximum depth of scour is maximum.Hereθis the angle the line drawn at the inlet of bend to the line joining the centre of curvature and any point on the outer portion of the bend.
文摘Change silt charge of water in the rivers can negatively be reflected in throughput the rivers beds,stability of coast,change of river structures,disappearance of boggy places,etc.In work questions of variability silt charge waters in the river Sluch in time and on length of the river are considered.It is revealed that in time average and maximal silt charge waters decrease.While on length of the river change silt charge waters is shown not precisely,similar on some increase silt charge waters to a mouth of the river.The researches led by the factorial analysis and graphic-analytical method on the basis of long-term materials of measurement of charges of water have shown that,on a part of posts average depth of water in the river grows,and on others-cyclically changes with the general tendency to reduction.Average speed in them,accordingly,falls and grows.Stratification of interrelations of a silt charge with other factors on years is observed.The reasons of reduction of a silt charge are:1)agrarian and forest meliorative actions on a catchments of the river,hydraulic engineering construction;2)grassy bed of the river;3)change of a climate that promotes growth of temperature of a surface of soils and grassy bed of the river.In developed natural-climatic conditions expediently application on reservoirs of the antierosion organization of territory of the land tenure including agrarian-forests-meliorative actions that will allow to adjust outflow of a moisture from reservoirs to lower warming up of a surface of the soils,to provide against a high water protection and it will favorably be reflected in manufacture of agricultural production.
基金The authors would like to acknowledge the South African National Research Foundation for funding this work.
文摘Although PVDF flat sheet membranes have been widely tested in MD,their synthesis and modifications currently require increased use of green and inexpensive materials.In this study,flat sheet PVDF membranes were synthesized using phase inversion and water as the pore former.Remarkably,the water added in the casting solution improved the membrane pore sizes;where the maximum pore size was 0.58μm.Also,the incorporation of f-SiO2NPs in the membrane matrix considerably enhanced the membrane hydrophobicity.Specifically,the membrane contact angles increased from 96°to 153°.Additionally,other parameters investigated were mechanical strength and liquid entry pressure(LEP).The maximum recorded values were 2.26 MPa and 239 kPa,respectively.The modified membranes(i.e.,using water as the pore former and f-SiO2NPs)were the most efficient,showing maximum salt rejection of 99.9%and water flux of 11.6 LMH;thus,indicating their capability to be used as efficient materials for the recovery of high purity water in MD.
文摘In the last decade,the construction of communication routes has intensified globally.As a result,many case studies have emerged related to the presence of saturated clayey soils in the foundation ground.In order to speed up the execution of highways and railways in a safely manner,the designers use different methods for improving soft clays in terms of compressibility.The present paper aims to evaluate the efficiency of an electrochemical method used for the dewatering of a soft montmorillonite clay subgrade.The effects on the consolidation process are analyzed for the final conclusions.The advantages of the method are briefly discussed,and some potential areas for scientific research are proposed.
基金The authors gratefully acknowledge the State University of Zanzibar,Chief Government Chemist Laboratory Agency,University of Daresalam for supporting during sample collection,storage and analysis.We also thank Farid Mpatani,Hasasn Ali Juma,Peter Gofrey Ndosi for their untiring assistance.
文摘Aim of the study was to assess the physicochemical characteristics of rainwater at urban and rural(north B)Unguja.Twenty four(24)rainwater samples were analyzed for pH,electrical conductivity(EC)and total dissolved solids(TDS)and cations:calcium(Ca^2+),copper(Cu^2+),iron(Fe^2+),chromium(Cr VI),and anions:fluoride(F^-),nitrite and sulfate(SO4^2-).The investigated physicochemical parameters in the rainwater samples were within the permissible limits of the World Health Organization(WHO)drinking water quality guidelines.The ranges of concentration for the physical parameters analyzed were;pH:(5.8-7.7),EC:(5.08-35.6μS/cm),TDS:(1.68-20.16 mg/L,Ca:(0.163-24.331 mg/L),Cr:(VI):(BDL-0.029 mg/L),Cu:(BDL-0.085 mg/L);Fe:(BDL-0.068),anions were SO4^2-:(BDL-5.00 mg/L)and F^-:(BDL-0.5 mg/L).Nevertheless,there was no significant difference for the measured parameters between urban and rural areas.This is a good indication that the air quality in Zanzibar is remarkably not polluted with respect to the parameters studied.
文摘This study investigated coal-mine drainage(AMD)and municipal wastewater(MWW)contaminant concentrations and conducted the combined treatment in phases I and II:phase I,evaluating the effects of mixing the two based on the extent of acid neutralization and metals removal;phase II:conducting anaerobic batch reactor treatment of AMD and MWW under varying COD/sulfate ratios(0.04-5.0).In phase I,acid mine drainage water quality conditions are as follows:pH 4.5,acidity 467.5 mg/L as CaCO3,alkalinity 96.0 mg/L as CaCO3,Cl-11.8 mg/L,SO42-1722 mg/L,TDS 2757.5 mg/L,TSS 9.8 mg/L,BOD 14.7 mg/L,Fe 138.1 mg/L,Mg 110.8 mg/L.Mn 7.5 mg/L,Al 8.1 mg/L,Na 114.2 mg/L,and Ca 233.5 mg/L.Results of the mixing experiments indicated significant removal of selected metals(Fe 85~98%,Mg 0~65%,Mn 63~89%,Al 98~99%,Na 0~30%),acidity(77~95%)from the mine water and pH was raised to above 6.3.The Phase II results suggested under the wide range of COD/sulfate ratios,COD and sulfate removal varied from 37.4%-100%and 0%-93.5%respectively.During biological treatment,alkalinity was generated which leads to pH increase to around 7.6-8.5.The results suggested feasibility of the proposed technology for co-treatment of AMD and MWW.A conceptual design of co-treatment system which is expected to remove a matrix of pollutants has been provided to utilize all the locally available water resources to achieve the optimum treatment efficiency.The technology also offers an opportunity to significantly reduce capital and operating costs compared to the existing treatment methodologies used.Featured Application:In this study,we have measured the concentrations of contaminants in acid mine drainage(AMD)and municipal wastewater(MWW)and conducted the combined treatment in phases I and II.This is significant because in previous years there was a massive fish kill that is linked to the high total dissolved solids(TDS)and salinity content in the water.With the current proposed combined treatment technology,it shows high potential in reducing TDS and salinity content in the
文摘Vortex-induced vibration(VIV)of multiple circular cylinders elastically connected together in a side-by-side arrangement subject to steady flow is investigated numerically at a low Reynolds number of 150 and a mass ratio of 2.Simulations are conducted for two-,five-and ten-cylinder systems over a wide range of reduced velocities.The aim of the study is to identify the high-amplitude response range of the reduced velocity for the multiple degree of freedom vibration system and identify the difference between the responses of the single-and multiple-degree-of-freedom vibrations.Unlike the single cylinder case,distinct lock-in between the response frequency and any of the structural natural frequencies in a wide range of reduced velocity is not observed in the multiple-cylinder cases.Instead,the response frequency increases continuously with increasing reduced velocity.High response amplitudes are found when the response frequency is between the first and the highest modal frequencies.In a multiple-cylinder system,the single-mode response,where the vibration is dominated by one mode,can be only found in low reduced velocity range.In the single-mode branch,the dominance of a single mode shape in the response can be clearly identified except at the boundary reduced velocity between two modes.The maximum response amplitude occurs in the multiple-mode response and interaction between the vortices in the wake of the cylinders is strong when the response amplitudes are high.
文摘Climate change can alter the status quo of the world as we know today.Water resources may also be influenced by these plausible impacts.The common perception is that these changes may exacerbate the situation of water resources in arid and semi-arid regions,such as the Middle-East,which are experiencing mild to severe water stress due to limited water availability and growing water demands.In that spirit,this study aims to investigate the possible impacts of climate change on surface water in Maharlou Lake basin,Iran.Reportedly,this basin has already shown some symptoms of the water-related crisis,which highlights the importance of conducting climate change studies in this region.The CansESM2 model was employed to predict the basin’s climatic response under various climate change scenarios.The hydrologic response of the basin was,then,simulated using IHACRES.The results have demonstrated a 4%decrease in average annual rainfall,a 2%increase in average annual temperature,and,finally,a 24%decrease in average annual streamflow of the basin in the(2010-2099)time window.While the results suggest that recent water-related challenges in the basin might have caused by climate change,further in-depth studies are required to reveal the exact reasons.
文摘Pre-stressed structure and its application for civil engineering.Specificity of external loads of ships.Corresponded specificity of controllable pre-stressing.An example of pre-stressed structure and an decreasing estimation of its mass(about 10%of the full displacement).Possibility of wider application.
文摘A three dimensional model to predict the hydro-mechanical state of unsaturated and deformable material during hot air drying has been proposed.The material viscoelastic behaviour was formulated using Bishop’s effective stress theory for partially saturated material using the liquid saturation as the Bishop parameter.The hydro-thermal and mechanical equations were coupled by the fluid pressure and the solid matter velocity.The model was applied to a deformable material(innovative clay-cellulose fibers composite)subjected to convective drying.A generalized Maxwell model with five elements,whose parameters were measured experimentally and correlated to water content was used to describe the material’s viscoelastic behavior.The hydro-thermal part of the proposed model was validated on the basis of a comparison of experimental and simulated drying rate curves.The Von Mises stress was simulated and compared to the experimental tensile strength in order to predict the time and the region of material failure.For a drying process at 95°C,the region of failure risk was identified.The failure may occur on the lateral surface of the slab in contact with air at a drying time of 2.5h.
文摘The independent LNG(Liquified Nature Gas)containment is widely used for small or medium-sized LNG carrier and ship using LNG as fuels.The common tank pattern includes single-spherical-cylindrical tank and double-spherical-cylindrical tank,which is the key to design the hull structure and its support.The support is designed to connect the hull structure and LNG tank.Its main functions are heat transferring and force loading.This paper focus on the temperature field distribution of hull and its support structure.The thermal boundary conditions are simulated according to the heat transfer action,such as thermal convection,heat conduction and thermal radiation.The method on how to carry out thermal analysis is presented for an independent LNG containment.The case study is carried out with two typical independent LNG tanks.One is a tank with double spherical cylindrical in the LNG carrier,and the other is a tank with single spherical cylindrical on the deck of the ship using LNG as fuels.The result shows the method presented in this paper is a good reference for the structural design with independent LNG containment.
文摘This document provides some guidelines to authors for submission in order to work towards a seamless submission process.While complete adherence to the following guidelines is not enforced,authors should note that following through with the guidelines will be helpful in expediting the copyediting and proofreading processes,and allow for improved readability during the review process.
文摘This study is based on the hypothesis that the implementation of Integrated Water Resources Management(IWRM)tools in the Oueme watershed has not led to a systematic improvement in the degree of IWRM implementation in the Oueme Valley in Benin.Methodologically,data were collected through a semi-structured survey of stakeholder families in the study area using snowball sampling.The tool used was the form developed by the United Nations to collect data to assess the level of IWRM implementation.The four(4)assessment criteria,each covering a key component of IWRM,are the enabling environment,institutions and participation,management tools and financing.The results obtained per criteria according to the stepwise methodology adopted reveal on average a degree of implementation of 40 on a scale of 0 to 100 in the Oueme basin.This value varies according to the geographical area and the factors considered.This study,which is a decision-making tool,provides a guide for governments to monitor the progress of integrated water resources management in their territory.
文摘Ice Engineering is associated with how to solve challenges from different kinds of ice,such as,sea ice,river ice,lake ice,icing,and snow in cold regions.The aim is to design special structures which could resist structural and global impact from drifting ice and freezing ice.The foundation of ice engineering is to study ice properties and its action on various structures,icing process within ice mechanics by using theoretical analysis,numerical simulation,model scale tests and field measurements.Ice is a kind of non-uniform material and its properties depends on many factors such as loading rate,temperature,freezing disturbance.The scope of Ice Engineering covers the science and engineering projects in cold regions,especially for offshore oil and gas,Arctic shipping,and offshore renewable energy.
文摘have been done in the past by many researchers.Many factors which affect scour around piers such as shape of piers,size,positioning and orientation etc.have been studied in detail by them.However,similar studies in meandering channels are scanty.Very few researchers have studied the effect of angular displacement which has considerable effects of scour around bridge piers.In this paper an attempt has been made to carry out a detailed study of angular displacement on scour.A constant diameter bridge pier of circular shape has been tested in a meandering channel bend with bend angle as 800.The test bed was prepared by using uniform sand having d50 as 0.27 mm and run was taken for a discharge of 2.5 l/s.
文摘Surface water samples were collected from selected locations along river Panchaganga,from Kolhapur to Narsobawadi during April 2019.Physicochemical parameters were determined in the laboratory and chemical mass balance approach was adopted to estimate the individual ionic loads in the river water.Streeter-Phelps equation was applied to derive a relationship between DO and BOD_(5).Model parameters such as De-oxygenation Rate(K_(d))and Re-aeration Rates(K_(r))were optimized using different empirical methods.The result of chemical mass balance showed an increase in the loading of various ions from upstream to downstream which could be attributed to agricultural and industrial wastes that enter the main stream.De-oxygenation rate and re-aeration constants were calculated using various empirical methods.DO sag curve was developed using Streeter Phelp’s model and compared with the observed parameters which showed a significant correlation.DO-BOD concentration observed along the course of the river indicated that the self-purification capacity of the river is high due to which the river regains the lost DO level at a distance less than 50 meters.
