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Water 2018, 10(7), 870; https://doi.org/10.3390/w10070870

On the Difference of River Resistance Computation between the k ε Model and the Mixing Length Model

1
College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China
2
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing 210098, China
3
National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai University, Nanjing 210098, China
*
Author to whom correspondence should be addressed.
Received: 22 May 2018 / Revised: 21 June 2018 / Accepted: 27 June 2018 / Published: 29 June 2018
(This article belongs to the Section Hydraulics)
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Abstract

River resistance characteristics, which can be reflected by the resistance factor, have an impact on flow and sediment transport. In the classical theory, Prandtl proposed the mixing length model for the simulation of the turbulence, and von Kármán established the logarithmic formula of the flow velocity distribution. Based on that, the expression of the resistance factor can be derived. With the development of the numerical technology, the kε model has been widely applied in the channels computation. However, for the different closure ways of the Reynolds stress in turbulence equations, the outcomes of the kε model and the Prandtl mixing length model are not exactly identical. In this paper, both qualitative and quantitative studies are carried out on the difference between these two models, with respect to the resistance factor. This difference is evaluated by the ratio of the resistance factor computed with the two models. The result shows that with the increment of the relative flow depth, the ratio first increases and then decreases. Moreover, it is also affected by the bed slope. Therefore, the difference should be taken into account when a comparison is made between the simulation results of the kε model and the classical theory of river mechanics. View Full-Text
Keywords: resistance k ε model; mixing length model; turbulence; open-channel uniform flow resistance k ε model; mixing length model; turbulence; open-channel uniform flow
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Dai, W.; Ding, M.; Zhang, H. On the Difference of River Resistance Computation between the k ε Model and the Mixing Length Model. Water 2018, 10, 870.

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