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Effects of Lifting Force on Bed Topography and Bed-Surface Sediment Size in Channel Bend |
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| Authors: | Jiun-Huei Jang Hsin-ya Ho Chin-lien Yen |
| Affiliation: | 1Associate Research Fellow, National Science and Technology Center for Disaster Reduction, Taipei, Taiwan, 23143 (corresponding author). E-mail: d88521017@ntu.edu.tw 2Deputy Director, Taiwan Typhoon and Flood Research Institute, National Applied Research Laboratories, Taipei, Taiwan, 10093. E-mail: hyh@ttfri.narl.org.tw 3Professor Emeritus, Dept. of Civil Engineering and Hydrotech Research Institute, National Taiwan Univ., Taipei, Taiwan, 10673. E-mail: clyen@ccms.ntu.edu.tw |
| Abstract: | In bed-load sediment transport, the lifting force plays an important role in reducing the friction between sediment particles and the bed surface, and it makes particle transportation by the shear force easier. Because the lifting force is related to vorticity, a three-dimensional (3D) numerical model incorporating large eddy simulations was applied to simulate the vorticity field in a channel bend. The results show that the distribution of vorticity is highly nonuniform, and it can lead to significant variations in lifting force and bed-load sediment transport per unit width in a channel bend. Relevant theories are modified on the basis of physical reasoning and then incorporated into numerical models to investigate the lifting-force effects on the bed topography and bed-surface sediment size gradation in a channel bend. With the lifting-force effects considered, it is shown that the errors in simulated bed topography can be reduced by approximately 40% and in bed-surface sediment size by 50%. |
| Keywords: | Lifting Friction Hydraulic bend Sediment transport Shear stress Bed loads Topography |