Vertical velocity in rectangular channel bends: numerical study and development of a prediction formula
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Up-welling and down-welling are formed in the inner and outer banks of the river bends, respectively. In this paper, a 3D numerical model is employed in order to study the effective parameters on the maximum value of the up-welling (wU(max)) and down-welling (wD(max)) in rectangular channel bends. A numerical model validated by the existing experimental data is applied to investigate the effects of different parameters on wU(max) and wD(max) over a wide range of flow conditions. The results revealed that the relative depth (water depth/bend radius) and bed resistance are the most effective parameters on wU(max) and wD(max), with a direct relationship. Moreover, based on the numerical results, two formulas are proposed for prediction of wU(max) and wD(max). Accuracy metrics such as root-mean-square error, bias and correlation coefficient indicated that the developed formulas can be applied successfully to approximate wU(max) and wD(max) for engineering application.
KeywordsChannel bends Up-welling Down-welling Numerical modeling New formulas
The authors would like to thank Professor Blanckaert for his valuable dataset. The authors also thank Ebrahim Jafari and Mohammad Peyro for their help in improving the manuscript.
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