Linear Theory of Velocity Redistribution for Flow in Compound Open Channels Under Inflow With Small Oblique Angles

XU Dong; HUANG Xionghe; JI Chunning; BAI Yuchuan

doi:10.21656/1000-0887.380183

Volume 39 Issue 7

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Article Navigation > Applied Mathematics and Mechanics > 2018 > 39(7): 785-797

XU Dong, HUANG Xionghe, JI Chunning, BAI Yuchuan. Linear Theory of Velocity Redistribution for Flow in Compound Open Channels Under Inflow With Small Oblique Angles[J]. Applied Mathematics and Mechanics, 2018, 39(7): 785-797. doi: 10.21656/1000-0887.380183

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Linear Theory of Velocity Redistribution for Flow in Compound Open Channels Under Inflow With Small Oblique Angles

doi: 10.21656/1000-0887.380183

State Key Laboratory of Hydraulic Engineering Simulation and Safety(Tianjin University), Tianjin 300072, P.R.China

Funds: The National Natural Science Foundation of China(51621092; 51579175;51009105)

Received Date: 2017-06-28
Rev Recd Date: 2018-05-23
Publish Date: 2018-07-15

Abstract

Abstract

The directions of flow in natural compound river channels are frequently influenced by the discharge and floodplainmain channel configuration, which may lead to a small intersection angle between the flow and the channel. Hence, lots of existent theories for floodplain flows under the assumption of uniform straight channels may be inapplicable. To investigate the influence of oblique inflow, shallow water equations were used to describe flow motion in compound open channels. The perturbation method was used with a small parameter of the oblique angle to derive the analytical solution for flow in compound open channels under inflow with small oblique angles. The solutions were verified with numerical simulation results and the flow velocity distributions agreed well. Theoretical results show that the obliquity of inlet flow lead to asymmetrical velocity distribution across the cross section of a compound channel, which is featured by an increase of velocity in the upstream side and a decrease in the downstream side of the main channel. Under an oblique angle of 13° and a floodplainmain channel water depth ratio of 3∶8, the flow velocity deviation may reach 21.8% of the value in the straight flow case. Such a deviation increases with the decreasing of the floodplainmain channel water depth ratio. The proposed modification to flow velocity distribution may improve the accuracy of hydrodynamic conditions for further research on sediment transport and evolutions of compound channel rivers.
- compound channel,
- small oblique angle inflow,
- perturbation method,
- linear theory

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