In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field h...In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer.Within the vegetated layer,an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted.In the non-vegetated layer,a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated.Based on the studied analytical model,a sensitivity analysis has been conducted to assess the influences of the drag (CD) and friction (Cf ) coefficients on the flow velocity.The investigated ranges of CD and Cf have also been compared to published values.The findings suggest that the CD and Cf values are non-constant at different depths and vegetation densities,unlike the constant values commonly suggested in literature.This phenomenon is particularly clear for flows with flexible vegetation,which is characterised by large deflection.展开更多
The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the re...The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-e model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning＇s roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases.展开更多
The interaction between waves and currents in the ocean often complicates the flow field around structures.In this study,a three-dimensional integrated numerical model was established to investigate the seabed respons...The interaction between waves and currents in the ocean often complicates the flow field around structures.In this study,a three-dimensional integrated numerical model was established to investigate the seabed response and liquefaction around a mono-pile under different wave-current interaction angles.In the present model,the Reynolds-averaged Navier-Stokes equations were used to simulate the flow field,and the Biot's poro-elastic theory was adopted to calculate the seabed response caused by crossing wave-current loading.Unlike previous studies,the load on the mono-pile was considered,and the wave-current interaction angle was extended to 180°,which was more in line with practical engineering problems.The numerical results were in a good agreement with the experimental measurements.The results indicated that waves interacted with currents in a large angle could result in a large momentary liquefaction depth of the seabed.The parametric studies proved that the position of the front and two sides of the pile was relatively safer compared with that of the leeside of the pile,and the surface of the seabed downstream of the pile was liable to liquefy.展开更多
Pile foundations have been widely used in offshore engineering.In this study,a three-dimensional numerical model was used to investigate the seabed response around a mono-pile under wave-current loading.Reynolds-avera...Pile foundations have been widely used in offshore engineering.In this study,a three-dimensional numerical model was used to investigate the seabed response around a mono-pile under wave-current loading.Reynolds-averaged Navier-Stokes equations were used to simulate the flow field,and Biot's consolidation equations were used for simulating the response of a porous seabed.The pore water pressure within soil and the effective stress along the depth of the seabed were simulated for various current velocities,with currents traveling either along or against the wave.Results indicate that the current has a significant effect on the effective stress and the pore water pressure distributions,which increases with the current velocity,and that the current traveling against the wave increases the liquefaction depth of the porous seabed.展开更多
The deformed microstructure evolution of depleted uranium impacted by steel projectile at a velocity of50m/s was investigated by means of confocal laser scanning microscope,electron backscatter diffraction,transmissio...The deformed microstructure evolution of depleted uranium impacted by steel projectile at a velocity of50m/s was investigated by means of confocal laser scanning microscope,electron backscatter diffraction,transmission electron microscope and indenter technique.The experimental results showed that the spherical cap crater was formed in depleted uranium target impacted by steel projectile,and the diameter and depth of the impacted crater were5.45and1.01mm,respectively.From crater rim to deep matrix,four deformed zones were classified,including twin fragmentation zone,high density deformation twin zone,low density deformation twin zone and matrix zone.Twinning was considered as the dominant plastic deformation mechanism of depleted uranium subjected to impact loadings.Besides twinning,the dislocation slipping also played an important role to accommodate the plastic deformation.Finally,the deformed microstructure evolution of depleted uranium under high velocity impact was proposed.展开更多
The offshore wind industry has been Hourishing globally over the past few decades because of the increasing demand for renewable energy.Different types of foundations have been adopted,including monopiles,gravity・base...The offshore wind industry has been Hourishing globally over the past few decades because of the increasing demand for renewable energy.Different types of foundations have been adopted,including monopiles,gravity・based structures,tripods,jackets,and pile groups for traditional offshore wind-farm foundations,as well as drag-embedment anchors(DEAs)with associated subsea structures(i.e.,tensioners,clump weights,and chains)for foundations of floating windfarms.Local scour and liquefaction issues are significant to the security of offshore windfarm foundations and foundation stability(Guan et al.,2019;Whitehouse et al.,2011;Zhu et al.,2018).展开更多
A self-healing and recyclable carbon tube/epoxy adhesive was prepared by epoxy monomer with Diels-Alder （DA） bonds, diethylenetriamine and polyethyleneimine modified multi-wall carbon nanotubes （MWCNTs）. The self-...A self-healing and recyclable carbon tube/epoxy adhesive was prepared by epoxy monomer with Diels-Alder （DA） bonds, diethylenetriamine and polyethyleneimine modified multi-wall carbon nanotubes （MWCNTs）. The self-healing and recyclable ability was attained by thermally reversible Diels-Alder reaction between furan and maleimide in the epoxy monomer. By controlling the molar ratio of furfuryl glycidyl ether and 4,4＇-methylenebis（N-phenylmaleimide）, the glass transition temperature and mechanical properties of MWCNTs/epoxy adhesives were varied. The self-healing properties of MWCNTs/epoxy polymers were evaluated by lap shear experiment and the results showed that the MWCNTs/epoxy adhesives exhibited enhanced mechanical properties and excellent self-healing ability under heat stimulus. The healing efficiency was related to the molecule mobility and the conversion of DA reaction between furan and maleimide. The MWCNTs/epoxy adhesives also displayed excellent recyclable ability by transforming into soluble polymer under heating. These materials offer a wide range of possibilities to produce materials with healing and recyclable ability and have the potential to bring great benefits to our daily lives by enhancing the safety, performance, and lifetime of products.展开更多
文摘In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer.Within the vegetated layer,an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted.In the non-vegetated layer,a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated.Based on the studied analytical model,a sensitivity analysis has been conducted to assess the influences of the drag (CD) and friction (Cf ) coefficients on the flow velocity.The investigated ranges of CD and Cf have also been compared to published values.The findings suggest that the CD and Cf values are non-constant at different depths and vegetation densities,unlike the constant values commonly suggested in literature.This phenomenon is particularly clear for flows with flexible vegetation,which is characterised by large deflection.
基金supported by the National Natural Science Foundation of China(Grants No.11361002 and 91230111)the Natural Science Foundation of Ningxia,China(Grant No.NZ13086)+1 种基金the Project of Beifang University of Nationalities,China(Grant No.2012XZK05)the Foreign Expert Project of Beifang University of Nationalities,China,and the Visiting Scholar Foundation of State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,China(Grant No.2013A011)
文摘The upper reach of the Yellow River from Daliushu to Shapotou consists of five bends and has complex topography. A two-dimensional Re-Normalisation Group （RNG） k-ε model was developed to simulate the flow in the reach. In order to take the circulation currents in the bends into account, the momentum equations were improved by adding an additional source term. Comparison of the numerical simulation with field measurements indicates that the improved two-dimensional depth-averaged RNG k-e model can improve the accuracy of the numerical simulation. A rapid adaptive algorithm was constructed, which can automatically adjust Manning＇s roughness coefficient in different parts of the study river reach. As a result, not only can the trial computation time be significantly shortened, but the accuracy of the numerical simulation can also be greatly improved. Comparison of the simulated and measured water surface slopes for four typical cases shows that the longitudinal and transverse slopes of the water surface increase with the average velocity upstream. In addition, comparison was made between the positions of the talweg and the main streamline, which coincide for most of the study river reach. However, deviations between the positions of the talweg and the main streamline were found at the junction of two bends, at the position where the river width suddenly decreases or increases.
基金supported by the Key Project of NSFC-Shangdong Joint Research Funding POW3C(Grant No.U1906230).
文摘The interaction between waves and currents in the ocean often complicates the flow field around structures.In this study,a three-dimensional integrated numerical model was established to investigate the seabed response and liquefaction around a mono-pile under different wave-current interaction angles.In the present model,the Reynolds-averaged Navier-Stokes equations were used to simulate the flow field,and the Biot's poro-elastic theory was adopted to calculate the seabed response caused by crossing wave-current loading.Unlike previous studies,the load on the mono-pile was considered,and the wave-current interaction angle was extended to 180°,which was more in line with practical engineering problems.The numerical results were in a good agreement with the experimental measurements.The results indicated that waves interacted with currents in a large angle could result in a large momentary liquefaction depth of the seabed.The parametric studies proved that the position of the front and two sides of the pile was relatively safer compared with that of the leeside of the pile,and the surface of the seabed downstream of the pile was liable to liquefy.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC1404200)the National Natural Science Foundation of China(Grant No.51479053)the Marine Renewable Energy Research Project of the State Oceanic Administration(Grant No.GHME2015GC01).
文摘Pile foundations have been widely used in offshore engineering.In this study,a three-dimensional numerical model was used to investigate the seabed response around a mono-pile under wave-current loading.Reynolds-averaged Navier-Stokes equations were used to simulate the flow field,and Biot's consolidation equations were used for simulating the response of a porous seabed.The pore water pressure within soil and the effective stress along the depth of the seabed were simulated for various current velocities,with currents traveling either along or against the wave.Results indicate that the current has a significant effect on the effective stress and the pore water pressure distributions,which increases with the current velocity,and that the current traveling against the wave increases the liquefaction depth of the porous seabed.
基金Project(2014B0301046)supported by the Science Development Fund of China Academy of Engineering PhysicsProject(51401187)supported by the National Natural Science Foundation of China
文摘The deformed microstructure evolution of depleted uranium impacted by steel projectile at a velocity of50m/s was investigated by means of confocal laser scanning microscope,electron backscatter diffraction,transmission electron microscope and indenter technique.The experimental results showed that the spherical cap crater was formed in depleted uranium target impacted by steel projectile,and the diameter and depth of the impacted crater were5.45and1.01mm,respectively.From crater rim to deep matrix,four deformed zones were classified,including twin fragmentation zone,high density deformation twin zone,low density deformation twin zone and matrix zone.Twinning was considered as the dominant plastic deformation mechanism of depleted uranium subjected to impact loadings.Besides twinning,the dislocation slipping also played an important role to accommodate the plastic deformation.Finally,the deformed microstructure evolution of depleted uranium under high velocity impact was proposed.
基金support from the Major International Collaboration Research Project P0W3M(Grant No.51920105013)of the National Natural Science Foundation of China(NSFC)the Key Project of NSFC—Shangdong Joint Research Funding POW3C(Grant No.U1906230).
文摘The offshore wind industry has been Hourishing globally over the past few decades because of the increasing demand for renewable energy.Different types of foundations have been adopted,including monopiles,gravity・based structures,tripods,jackets,and pile groups for traditional offshore wind-farm foundations,as well as drag-embedment anchors(DEAs)with associated subsea structures(i.e.,tensioners,clump weights,and chains)for foundations of floating windfarms.Local scour and liquefaction issues are significant to the security of offshore windfarm foundations and foundation stability(Guan et al.,2019;Whitehouse et al.,2011;Zhu et al.,2018).
基金financially supported by the National Natural Science Foundation of China(Nos.51573172,11405149 and 51401187)the Science and Technology Planning Project of Sichuan Province(No.SCXSDTR15001)Director’s Funds of China Academy of Engineering Physics(No.SJZ201506)
文摘A self-healing and recyclable carbon tube/epoxy adhesive was prepared by epoxy monomer with Diels-Alder （DA） bonds, diethylenetriamine and polyethyleneimine modified multi-wall carbon nanotubes （MWCNTs）. The self-healing and recyclable ability was attained by thermally reversible Diels-Alder reaction between furan and maleimide in the epoxy monomer. By controlling the molar ratio of furfuryl glycidyl ether and 4,4＇-methylenebis（N-phenylmaleimide）, the glass transition temperature and mechanical properties of MWCNTs/epoxy adhesives were varied. The self-healing properties of MWCNTs/epoxy polymers were evaluated by lap shear experiment and the results showed that the MWCNTs/epoxy adhesives exhibited enhanced mechanical properties and excellent self-healing ability under heat stimulus. The healing efficiency was related to the molecule mobility and the conversion of DA reaction between furan and maleimide. The MWCNTs/epoxy adhesives also displayed excellent recyclable ability by transforming into soluble polymer under heating. These materials offer a wide range of possibilities to produce materials with healing and recyclable ability and have the potential to bring great benefits to our daily lives by enhancing the safety, performance, and lifetime of products.
