This paper presents an experimental investigation of the circulation of the horseshoe vortex system within the equilibrium scour hole at a circular pier, with the data measured by an acoustic Doppler velocimeter （ADV...This paper presents an experimental investigation of the circulation of the horseshoe vortex system within the equilibrium scour hole at a circular pier, with the data measured by an acoustic Doppler velocimeter （ADV）. Velocity vector plots and vorticity contours of the flow field on the upstream plane of symmetry （y = 0 cm） and on the planes ：e3 cm away from the plane of symmetry Cv = ~3 cm） are presented. The vorticity and circulation of the horseshoe vortices were determined using the forward difference technique and Stokes theorem, respectively. The results show that the magnitudes of circulations are similar on the planes y = 3 cm and y = -3 cm, which are less than those on the plane y = 0 cm. The circulation decreases with the increase of flow shallowness, and increases with the densimetric Froude number. It also increases with the pier Reynolds number at a constant densimetric Froude number, or at a constant flow shallowness. The relative vortex strength （dimensionless circulation） decreases with the increase of the pier Reynolds number. Some empirical equations are proposed based on the results. The predicted circulation values with these equations match the measured data, which indicates that these equations can be used to estimate the circulation in future studies.展开更多
In the present study, the flow field around a circular pier is investigated with experimental measurements and numerical simulations. The transient flow patterns during erosion are studied in detail. The results show ...In the present study, the flow field around a circular pier is investigated with experimental measurements and numerical simulations. The transient flow patterns during erosion are studied in detail. The results show that the traditional equations of particle motion are not perfect for the calculation of the sand motion under this complex flow situation. The scouring agents, such as turbulent intensity, the fluctuating pressure and the vertical pressure gradient, having many effects on the sand motion with the increasing scouring depth, need to be considered in modifying the traditional model.展开更多
[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
文摘This paper presents an experimental investigation of the circulation of the horseshoe vortex system within the equilibrium scour hole at a circular pier, with the data measured by an acoustic Doppler velocimeter （ADV）. Velocity vector plots and vorticity contours of the flow field on the upstream plane of symmetry （y = 0 cm） and on the planes ：e3 cm away from the plane of symmetry Cv = ~3 cm） are presented. The vorticity and circulation of the horseshoe vortices were determined using the forward difference technique and Stokes theorem, respectively. The results show that the magnitudes of circulations are similar on the planes y = 3 cm and y = -3 cm, which are less than those on the plane y = 0 cm. The circulation decreases with the increase of flow shallowness, and increases with the densimetric Froude number. It also increases with the pier Reynolds number at a constant densimetric Froude number, or at a constant flow shallowness. The relative vortex strength （dimensionless circulation） decreases with the increase of the pier Reynolds number. Some empirical equations are proposed based on the results. The predicted circulation values with these equations match the measured data, which indicates that these equations can be used to estimate the circulation in future studies.
文摘In the present study, the flow field around a circular pier is investigated with experimental measurements and numerical simulations. The transient flow patterns during erosion are studied in detail. The results show that the traditional equations of particle motion are not perfect for the calculation of the sand motion under this complex flow situation. The scouring agents, such as turbulent intensity, the fluctuating pressure and the vertical pressure gradient, having many effects on the sand motion with the increasing scouring depth, need to be considered in modifying the traditional model.
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.
