Knowledge of the equilibrium bed-concentration is vital to mathematical modeling of the river-bed deformation associated with suspended load but previous investigations only daelt with the reference concentra-tion of ...Knowledge of the equilibrium bed-concentration is vital to mathematical modeling of the river-bed deformation associated with suspended load but previous investigations only daelt with the reference concentra-tion of uniform sediment because of difficulties in observation of the bed-concentration.This work is a first at-tempe to develop a theoretical formula for the equilibrium bed-concentration of any fraction of nonumiform sedi-ment defined at the bed-surface.The formula is based on a stochastic-mechanistic model for the exchange of nonumiform sediment near the bed,and described as a function of incipient motion probability,non-ceasing probability,pick-up probability,and the ratio of the average single-step continuous motion time to static time.Comparison of bed-concentration calculated from the proposed formula with the measured data showed satisfac-tory agreement,indicating the present formula can be used for solving the differential equation governing the notion of suspended load.展开更多
A conception of exposure degree is used in this article to account for the hiding and exposure mechanism of nonuniform sediment transport. The force arms of particles on the bed slope are assumed to be a function of t...A conception of exposure degree is used in this article to account for the hiding and exposure mechanism of nonuniform sediment transport. The force arms of particles on the bed slope are assumed to be a function of the exposure degree, which is stochastically related to the size and gradation of bed materials. Based on this conception, the formula for the angle of repose of nonuniform sediment is developed. The angle of repose of nonuniform sediment is experimentally investigated in rotation drum at the rolling motion of sediment particles. The nonuniform sediment is gotten from the mixture of two kinds of uniform sediment with different weight ratios and two experimental plans that one for changing the weight ratio of two kinds of uniform sediment from 1：9 to 9：1 and the other changing the uniform sediment size and weight ratio are used. The effect of the rotation speed and the filling degree on the angle of repose is investigated, too. Finally, the formula has been tested against a wide range of laboratory data, the prediction by the newly proposed formulas is very good.展开更多
文摘Knowledge of the equilibrium bed-concentration is vital to mathematical modeling of the river-bed deformation associated with suspended load but previous investigations only daelt with the reference concentra-tion of uniform sediment because of difficulties in observation of the bed-concentration.This work is a first at-tempe to develop a theoretical formula for the equilibrium bed-concentration of any fraction of nonumiform sedi-ment defined at the bed-surface.The formula is based on a stochastic-mechanistic model for the exchange of nonumiform sediment near the bed,and described as a function of incipient motion probability,non-ceasing probability,pick-up probability,and the ratio of the average single-step continuous motion time to static time.Comparison of bed-concentration calculated from the proposed formula with the measured data showed satisfac-tory agreement,indicating the present formula can be used for solving the differential equation governing the notion of suspended load.
基金supported by the National Natural Science Foundation of China (Grant Nos.50739002,50979064)
文摘A conception of exposure degree is used in this article to account for the hiding and exposure mechanism of nonuniform sediment transport. The force arms of particles on the bed slope are assumed to be a function of the exposure degree, which is stochastically related to the size and gradation of bed materials. Based on this conception, the formula for the angle of repose of nonuniform sediment is developed. The angle of repose of nonuniform sediment is experimentally investigated in rotation drum at the rolling motion of sediment particles. The nonuniform sediment is gotten from the mixture of two kinds of uniform sediment with different weight ratios and two experimental plans that one for changing the weight ratio of two kinds of uniform sediment from 1：9 to 9：1 and the other changing the uniform sediment size and weight ratio are used. The effect of the rotation speed and the filling degree on the angle of repose is investigated, too. Finally, the formula has been tested against a wide range of laboratory data, the prediction by the newly proposed formulas is very good.
