As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. B...As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.展开更多
The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab- lishing behaviors are appearing. A physical model test was used to forecast the scou...The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab- lishing behaviors are appearing. A physical model test was used to forecast the scouring and silting trends of the lower Yellow River. Based on water and sediment data from the lower Yellow River during the period from 1960 to 2012, and using a statistical method, this paper analyzed the sediment transport in sediment-laden flows with different discharges and sediment concentrations in the lower Yellow River. The results show that rational water-sediment regulation is necessary to avoid silting in the later sediment-retaining period. The combination of 3 000 m^3/s 〈 Q 〈 4 000 m^3/s and 20 kg/m^3 〈 S 〈 60 kg/m^3 （where Q is the discharge and S is the sediment concentration） at the Huayuankou section is considered an optimal combination for equilibrium sediment transport in the lower Yellow River over a long period of time.展开更多
This study focuses on the Lower Yellow River(LYR),which has experienced continuous erosion since the operation of Xiaolangdi Reservoir in 1999,and its spatiotemporal variation process is complex.Based on the single-st...This study focuses on the Lower Yellow River(LYR),which has experienced continuous erosion since the operation of Xiaolangdi Reservoir in 1999,and its spatiotemporal variation process is complex.Based on the single-step mode of the Delayed Response Model(DRM),we proposed a calculation method for simulating the accumulated erosion and deposition volume in the LYR.The coefficient of determination R^(2)between the calculated and measured values from 2000 to 2020 is 0.99.Currently,the LYR is undergoing continuous erosion,however the erosion rate is gradually slowing down,and the difference between the equilibrium and calculated values of accumulated erosion and deposition volume gradually decreases,which means riverbed erosion has a tendency towards equilibrium.Additionally,we derive a formula to simulate the spatial distribution of the main channel accumulated erosion volume per unit river length in the LYR based on the non-equilibrium suspended sediment transport equation.The coefficient of determination R^(2)between the fitted values and measured values from 2003 to 2015 is approximately 0.98-0.99,with a relative error of approximately 6.2%.The findings in this research suggest that under the current background of decreasing sediment inflow and continuous erosion in the LYR,it takes approximately 3.0 years for the riverbed to achieve half of the erosion and deposition adjustment and approximately 13.0 years to achieve 95%of the adjustment.Moreover,the spatial distribution of accumulated main channel erosion volume in the LYR tends to become uniform with the continuous development of erosion.These results could provide a valuable reference for analysing the complex spatiotemporal variation process in the LYR.展开更多
Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about ...Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs)along the MYR,and it is necessary to determine the magnitude of recovery factor.Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material,a new formula is proposed for calculating the recovery factor including the effect of different BMCs,and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR.The results show that:(i)the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii)the mean recovery factors of the coarse,medium,and fine sediment fractions in the ZhichengShashi reach were 0.152,0.0012,and 0.0005,respectively,and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m3over a distance of 15 km;and(iii)the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations,and the spatial and temporal delay effects are inversely related to particle size and BMC.Consequently,the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.展开更多
基金the National Natural Science Foundation of China (Grand No. 10672024)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China
文摘As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.
基金supported by the National Natural Science Foundation of China(Grants No.51039004 and No.51079055)the High-Level Personnel Research Start-Up Funds of North China University of Water Resources and Electric Power(Grant No.201403)the Science and Technology Research Project of the Education Department of Henan Province(Grant No.14A570001)
文摘The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab- lishing behaviors are appearing. A physical model test was used to forecast the scouring and silting trends of the lower Yellow River. Based on water and sediment data from the lower Yellow River during the period from 1960 to 2012, and using a statistical method, this paper analyzed the sediment transport in sediment-laden flows with different discharges and sediment concentrations in the lower Yellow River. The results show that rational water-sediment regulation is necessary to avoid silting in the later sediment-retaining period. The combination of 3 000 m^3/s 〈 Q 〈 4 000 m^3/s and 20 kg/m^3 〈 S 〈 60 kg/m^3 （where Q is the discharge and S is the sediment concentration） at the Huayuankou section is considered an optimal combination for equilibrium sediment transport in the lower Yellow River over a long period of time.
基金National Natural Science Foundation of China,No.U2243218。
文摘This study focuses on the Lower Yellow River(LYR),which has experienced continuous erosion since the operation of Xiaolangdi Reservoir in 1999,and its spatiotemporal variation process is complex.Based on the single-step mode of the Delayed Response Model(DRM),we proposed a calculation method for simulating the accumulated erosion and deposition volume in the LYR.The coefficient of determination R^(2)between the calculated and measured values from 2000 to 2020 is 0.99.Currently,the LYR is undergoing continuous erosion,however the erosion rate is gradually slowing down,and the difference between the equilibrium and calculated values of accumulated erosion and deposition volume gradually decreases,which means riverbed erosion has a tendency towards equilibrium.Additionally,we derive a formula to simulate the spatial distribution of the main channel accumulated erosion volume per unit river length in the LYR based on the non-equilibrium suspended sediment transport equation.The coefficient of determination R^(2)between the fitted values and measured values from 2003 to 2015 is approximately 0.98-0.99,with a relative error of approximately 6.2%.The findings in this research suggest that under the current background of decreasing sediment inflow and continuous erosion in the LYR,it takes approximately 3.0 years for the riverbed to achieve half of the erosion and deposition adjustment and approximately 13.0 years to achieve 95%of the adjustment.Moreover,the spatial distribution of accumulated main channel erosion volume in the LYR tends to become uniform with the continuous development of erosion.These results could provide a valuable reference for analysing the complex spatiotemporal variation process in the LYR.
基金the National Natural Science Foundation of China(Grant Nos.51725902,52009095,U2040215,U2240206,and 52109098)supported partly by the Postdoctoral Research Foundation of China(Grant No.BX2021228)Natural Science Foundation of Hubei Province(Grant No.2021CFA029)。
文摘Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs)along the MYR,and it is necessary to determine the magnitude of recovery factor.Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material,a new formula is proposed for calculating the recovery factor including the effect of different BMCs,and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR.The results show that:(i)the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii)the mean recovery factors of the coarse,medium,and fine sediment fractions in the ZhichengShashi reach were 0.152,0.0012,and 0.0005,respectively,and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m3over a distance of 15 km;and(iii)the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations,and the spatial and temporal delay effects are inversely related to particle size and BMC.Consequently,the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.
