Several typical formulas for bed load transport are examined based on field data. It is concluded that the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower t...Several typical formulas for bed load transport are examined based on field data. It is concluded that the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower transport rates. The main reason for the under-prediction is that Dp, the effective diameter of particles, is too large as a representative diameter of the bed material for gravel streams with partially movable bed. Performance of these formulas can be significantly improved if D35 is adopted instead of Dp.展开更多
A mathematical model is developed to simulate the change in mean velocity for the coexistent case of waves and current. The experimental results of mean velocity profile in a wave-current flume show the following feat...A mathematical model is developed to simulate the change in mean velocity for the coexistent case of waves and current. The experimental results of mean velocity profile in a wave-current flume show the following features: Eulerian mean current profile for following current is more uniformly distributed than the corresponding pure current case, whereas , the case of an opposing current leads to the more straight profile. This model is based on Eulerian mean framework, and motions of wave and current are solved simultaneously. The comparisons of numerical results and experimental data show that the mathematical model presented in this paper is reasonable and feasible.展开更多
According to the characters of the Miyun reservoir located in northeast Beijing, one-dimensional method is used to establish a mathematical model of temperature for the reservoir. In this model the heat exchange betwe...According to the characters of the Miyun reservoir located in northeast Beijing, one-dimensional method is used to establish a mathematical model of temperature for the reservoir. In this model the heat exchange between water surface and atmosphere, effective diffusion, inflows, outflows, and thermal advection are considered comprehensively. The effective diffusion coefficient, decay coefficient of short wave in water, etc, are calibrated based on the observed stratification data of 1991 in the reservoir. The mathematical model is verified through the agreement with the data of 1992. This model can be used to predict the temperature distribution along the vertical direction for the Miyun reservoir and other similar reservoir.展开更多
文摘Several typical formulas for bed load transport are examined based on field data. It is concluded that the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower transport rates. The main reason for the under-prediction is that Dp, the effective diameter of particles, is too large as a representative diameter of the bed material for gravel streams with partially movable bed. Performance of these formulas can be significantly improved if D35 is adopted instead of Dp.
文摘A mathematical model is developed to simulate the change in mean velocity for the coexistent case of waves and current. The experimental results of mean velocity profile in a wave-current flume show the following features: Eulerian mean current profile for following current is more uniformly distributed than the corresponding pure current case, whereas , the case of an opposing current leads to the more straight profile. This model is based on Eulerian mean framework, and motions of wave and current are solved simultaneously. The comparisons of numerical results and experimental data show that the mathematical model presented in this paper is reasonable and feasible.
文摘According to the characters of the Miyun reservoir located in northeast Beijing, one-dimensional method is used to establish a mathematical model of temperature for the reservoir. In this model the heat exchange between water surface and atmosphere, effective diffusion, inflows, outflows, and thermal advection are considered comprehensively. The effective diffusion coefficient, decay coefficient of short wave in water, etc, are calibrated based on the observed stratification data of 1991 in the reservoir. The mathematical model is verified through the agreement with the data of 1992. This model can be used to predict the temperature distribution along the vertical direction for the Miyun reservoir and other similar reservoir.
