[Objective]The aim was to study the simulation test of hydrodynamics process of erosion.[Method]Through the runoff scouring experiment,the property of soil erosion in Damaoqi grassland in Inner Mongolia was studied.Th...[Objective]The aim was to study the simulation test of hydrodynamics process of erosion.[Method]Through the runoff scouring experiment,the property of soil erosion in Damaoqi grassland in Inner Mongolia was studied.The process and mechanism of soil erosion were studied.[Result]The results of runoff scouring experiment on inner Damaoqi steppe showed that the mean flow velocity of change slope increased with the discharge of flow and slope gradient.The mean silt content rate,the mean sediment transport rate and the mean sheer stress all increased when the discharge of flow increased,which changed in parabolic form with the increase of slope gradient and the critical gradient is 25°.The relationship between the mean sediment transport rate and the mean sheer stress was linear.[Conclusion]The study provided theoretic basis for the report of soil erosion in grassland in China.展开更多
Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notab...Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notably bridges,would experience significant flooding for which they were not intended and would be submerged.The flow field and shear stress distribution around tandem bridge piers under pressurized flow conditions for various bridge deck widths are examined using a series of three-dimensional(3D)simulations.It is indicated that scenarios with a deck width to pier diameter(Ld/p)ratio of 3 experience the highest levels of turbulent disturbance.In addition,maximum velocity and shear stresses occur in cases with Ld/p equal to 6.Results indicate that increasing the number of piers from 1 to 2 and 3 results in the increase of bed shear stress by 24%and 20%respectively.Finally,five machine learning algorithms,including Decision Trees(DT),Feed Forward Neural Networks(FFNN),and three Ensemble models,are implemented to estimate the flow field and the turbulent structure.Results indicated that the highest accuracy for estimation of U,and W,were obtained using AdaBoost ensemble with R2=0.946 and 0.951,respectively.Besides,the Random Forest algorithm outperformed AdaBoost slightly in the estimation of V and turbulent kinetic energy(TKE)with R2=0.894 and 0.951,respectively.展开更多
The turbulent flow discharging under a sluice gate is one kind of typical flows with complicated boundaries in hydraulic and hydroelectric engineering, and the characteristics of its flow field and flow evolution are ...The turbulent flow discharging under a sluice gate is one kind of typical flows with complicated boundaries in hydraulic and hydroelectric engineering, and the characteristics of its flow field and flow evolution are important in engineering hydraulics. Although there were many studies in this regard, which mainly focus on the discharge capacity, the local scour and the mean flow field, some issues remain to be further investigated, for example, the variation of the mechanical energy during the scouring process, and the adjustment of the unsteady turbulent flow after the local scour with the downstream steady uniform flow. In this paper, the turbulent flow behind a sluice gate is divided into a rapidly varied flow region and a gradually varied flow region, and the above problems are investigated by theoretical analysis and numerical simulation. The main conclusions are as follows：（1） In the discharging process of the turbulent flow under a sluice gate, the river bed would be scoured continuously and the water–air interface is adjusted accordingly, which leads to a decrease of the mechanical energy of the total flow in the rapidly varied flow region, and the mechanical energy loss would also decrease with the increase of the time, yet the variation of the flow discharge under the sluice gate is very small.（2） In the link between the rapidly varied flow and the uniform flow downstream, the mean wall shear stress and the coefficient for the mechanical energy loss would decrease in the longitudinal direction, the decay of the turbulent kinetic energy near the free surface is much more significant than that near the bed in the longitudinal direction, and the mean turbulent kinetic energy in the section would decrease in the longitudinal direction and the decreasing rate is smaller than that of the mean wall shear stress.展开更多
基金Supported by the Scientific Research Program of China Institute of Water Resources and Hydropower Research (MKS2010001)
文摘[Objective]The aim was to study the simulation test of hydrodynamics process of erosion.[Method]Through the runoff scouring experiment,the property of soil erosion in Damaoqi grassland in Inner Mongolia was studied.The process and mechanism of soil erosion were studied.[Result]The results of runoff scouring experiment on inner Damaoqi steppe showed that the mean flow velocity of change slope increased with the discharge of flow and slope gradient.The mean silt content rate,the mean sediment transport rate and the mean sheer stress all increased when the discharge of flow increased,which changed in parabolic form with the increase of slope gradient and the critical gradient is 25°.The relationship between the mean sediment transport rate and the mean sheer stress was linear.[Conclusion]The study provided theoretic basis for the report of soil erosion in grassland in China.
基金supported by the National Natural Science Foundation of China (Grant Nos.52179060 and 51909024).
文摘Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notably bridges,would experience significant flooding for which they were not intended and would be submerged.The flow field and shear stress distribution around tandem bridge piers under pressurized flow conditions for various bridge deck widths are examined using a series of three-dimensional(3D)simulations.It is indicated that scenarios with a deck width to pier diameter(Ld/p)ratio of 3 experience the highest levels of turbulent disturbance.In addition,maximum velocity and shear stresses occur in cases with Ld/p equal to 6.Results indicate that increasing the number of piers from 1 to 2 and 3 results in the increase of bed shear stress by 24%and 20%respectively.Finally,five machine learning algorithms,including Decision Trees(DT),Feed Forward Neural Networks(FFNN),and three Ensemble models,are implemented to estimate the flow field and the turbulent structure.Results indicated that the highest accuracy for estimation of U,and W,were obtained using AdaBoost ensemble with R2=0.946 and 0.951,respectively.Besides,the Random Forest algorithm outperformed AdaBoost slightly in the estimation of V and turbulent kinetic energy(TKE)with R2=0.894 and 0.951,respectively.
基金Project supported by the Governmental Public Industry Research Special Funds for Projects(Grant No.201101005)
文摘The turbulent flow discharging under a sluice gate is one kind of typical flows with complicated boundaries in hydraulic and hydroelectric engineering, and the characteristics of its flow field and flow evolution are important in engineering hydraulics. Although there were many studies in this regard, which mainly focus on the discharge capacity, the local scour and the mean flow field, some issues remain to be further investigated, for example, the variation of the mechanical energy during the scouring process, and the adjustment of the unsteady turbulent flow after the local scour with the downstream steady uniform flow. In this paper, the turbulent flow behind a sluice gate is divided into a rapidly varied flow region and a gradually varied flow region, and the above problems are investigated by theoretical analysis and numerical simulation. The main conclusions are as follows：（1） In the discharging process of the turbulent flow under a sluice gate, the river bed would be scoured continuously and the water–air interface is adjusted accordingly, which leads to a decrease of the mechanical energy of the total flow in the rapidly varied flow region, and the mechanical energy loss would also decrease with the increase of the time, yet the variation of the flow discharge under the sluice gate is very small.（2） In the link between the rapidly varied flow and the uniform flow downstream, the mean wall shear stress and the coefficient for the mechanical energy loss would decrease in the longitudinal direction, the decay of the turbulent kinetic energy near the free surface is much more significant than that near the bed in the longitudinal direction, and the mean turbulent kinetic energy in the section would decrease in the longitudinal direction and the decreasing rate is smaller than that of the mean wall shear stress.
