Hydraulic calculation of steady uniform flows in trapezoidal compound open channels is studied. Based on the force balance of water in each sub-section, the average velocities of the main channel, side slope, and floo...Hydraulic calculation of steady uniform flows in trapezoidal compound open channels is studied. Based on the force balance of water in each sub-section, the average velocities of the main channel, side slope, and floodplain are derived. The lateral momentum exchanges between the sub-sections are expressed by using the apparent shear stress. To verify the model, seven groups of UK Flood Channel Facility （UK-FCF） measured data with a relative water depth between the floodplain and the main channel varying from 0.057 to 0.4 are used for comparison. The result shows that the calculated velocity is larger than the measured data when the relative water depth is small, while it is less than or close to the measured value in the case of a larger relative water depth. The influence of the apparent shear stress on the calculation of velocity on the floodplain is not obvious, while it is much greater on the main channel. The three-stage model is compared with Liu’s two-stage model, showing that the former can give a better prediction for a three-stage trapezoidal compound channel. Finally, the apparent shear stress is calculated and compared with the measured data. The result shows that the chosen values of the momentum transfer coefficients are appropriate.展开更多
The momentum transfer coefficient is an important parameter for determining the apparent shear stress at the vertical interface between the main channel and its associated flood plains,the cross-sectional mean velocit...The momentum transfer coefficient is an important parameter for determining the apparent shear stress at the vertical interface between the main channel and its associated flood plains,the cross-sectional mean velocity and the discharge capacity in compound channels. In this article,under the Boussinesq assumption and through analyzing the characteristics of velocity distribution in the interacting region between the main channel and its associated flood plain,the expression of momentum transfer coefficient was theoretically derived. On the basis of force balance,the expression of vertical apparent shear stress was obtained. By applying the experimental data from the British Engineering Research Council Flood Channel Facility (SERC-FCF),the relationship between the momentum transfer coefficient with the relative depth and the ratio of the flood plain width to the main channel width,was established,And hence the conveyance capacity in compound channels was calculated with Liu and Dong’s method. The computed results show that the momentum transfer coefficient relationship obtained is viable.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 50709025 and50979078)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry
文摘Hydraulic calculation of steady uniform flows in trapezoidal compound open channels is studied. Based on the force balance of water in each sub-section, the average velocities of the main channel, side slope, and floodplain are derived. The lateral momentum exchanges between the sub-sections are expressed by using the apparent shear stress. To verify the model, seven groups of UK Flood Channel Facility （UK-FCF） measured data with a relative water depth between the floodplain and the main channel varying from 0.057 to 0.4 are used for comparison. The result shows that the calculated velocity is larger than the measured data when the relative water depth is small, while it is less than or close to the measured value in the case of a larger relative water depth. The influence of the apparent shear stress on the calculation of velocity on the floodplain is not obvious, while it is much greater on the main channel. The three-stage model is compared with Liu’s two-stage model, showing that the former can give a better prediction for a three-stage trapezoidal compound channel. Finally, the apparent shear stress is calculated and compared with the measured data. The result shows that the chosen values of the momentum transfer coefficients are appropriate.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50579040, 50579041).
文摘The momentum transfer coefficient is an important parameter for determining the apparent shear stress at the vertical interface between the main channel and its associated flood plains,the cross-sectional mean velocity and the discharge capacity in compound channels. In this article,under the Boussinesq assumption and through analyzing the characteristics of velocity distribution in the interacting region between the main channel and its associated flood plain,the expression of momentum transfer coefficient was theoretically derived. On the basis of force balance,the expression of vertical apparent shear stress was obtained. By applying the experimental data from the British Engineering Research Council Flood Channel Facility (SERC-FCF),the relationship between the momentum transfer coefficient with the relative depth and the ratio of the flood plain width to the main channel width,was established,And hence the conveyance capacity in compound channels was calculated with Liu and Dong’s method. The computed results show that the momentum transfer coefficient relationship obtained is viable.
