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3D Investigation of Flow Hydraulic in U Shape Meander Bends with Constant, Decreasing and Increasing Width
Journal: Journal of River Engineering
Issue: Journal of River Engineering (Volume: 2, Issue: 3)
Author: Ali Liyaghat , Kamran Mohammadi , Mostafa Rahmanshahi
Keywords : Numerical simulation , Flow pattern , U shape bends , SSIIM 3-D model
Abstract:

In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since river bends are not uniform–some are divergent and others convergent–in this study, after the SSIIM 3-D model was calibrated using the result of measurements along a uniform 180° bend with a width of 0.6 m, two similar but convergent 180° bend, 0.6 m to 0.45 m wide and divergent 180° bend, 0.6 m to 0.75 m wide, was simulated using the SSIIM 3-D numerical model. Flow characteristics of the 180° bends, including lengthwise and vertical velocity profiles, primary and secondary flows, lengthwise and widthwise slopes of the water surface and the helical flow strength, were compared with each other. The verification results of the model show that the numerical model can effectively simulate the flow field in the uniform bend. In addition, this research indicates that, in a convergent channel, the maximum velocity path at a plane near the water surface crosses the channel’s centerline at about a 30° to 40° cross-section, while this occurs at about 50° cross section within divergent channel and about 55º for uniform one. The strength of the helical flow is generally greater in the divergent channel than in the uniform and convergent one, respectively. Also, unlike the uniform and divergent bends, the convergent bend exhibits no rotational cell against the main direction of secondary flow rotation at the 135° cross-section.

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