Experimental Study of Flow Division in a Smooth Circular Culvert

The idea of partitioning the flow has been widely used by hydraulic researchers and engineers. Currently, researchers claim that their models for the division lines are valid and yield good agreement with the experimental data from a channel flow that has a flat bed. It is not clear whether their models are still effective to model the division lines when the channel bed is curved. The aim of this paper is to examine the existence of division lines by analysing the distribution of mean velocity in a smooth culvert. The experiments reported here document a sufficient fact that it possible to observe the division lines from the velocity distribution. The method used to test the existence of the division line is to determine the normal distance from a boundary Ln, based on the local boundary shear stress. The model from Yang and Lim (YLM) is selected for considerations in this comparison because other models were unable to produce the theoretical division lines in these cases. The division lines obtained from YLM are also plotted for various experimental flows to demonstrate the relationship between the experimental and theoretical division lines. This experimental analytical method developed for division lines may be extended to any arbitrary channels in other channel flows based on the results of the distribution of velocity. Introduction Flow partitioning theory has been widely used in open channel flows by researchers such as Keulegan (1938), Einstein (1942), Yang and Lim (1997), Chien and Wan (1999), Guo and Julien (2005). Several mathematical treatments have been proposed to divide the cross section of a rectangular or trapezoidal channel into subsections (! INVALID CITATION ! ), but only a handful of experimental research has been conducted where these mathematical arguments were compiled, so the physical meaning of division lines is not understood very well (Yang, 2005). As for the division lines, it is easy to infer that the flow region is dividable if the shear stress measured along these lines is zero, but achieving accurate Reynolds shear stress measurements is very difficult relative to the mean velocity measurements. Currently, there are no specially designed experiments to verify them or the models, not to mention whether the existence of division lines can be inferred from the mean velocity profiles. Although the concept of flow partition is widely accepted, an extensive literature review reveals that there is no research work on flow partitioning in a culvert. The primary motivation for partitioning the flow in the cross section of a smooth open channel stemmed from the flow of wastewater in sewers and drainage system. In these cases, the local shear stress needs to be determined in order to prevent sewer erosion (! INVALID CITATION ! ). The study of flow partitioning in a culvert is also significant in various engineering applications such as estimating the International Conference on Manufacturing Engineering and Intelligent Materials (ICMEIM 2017) Copyright © 2017, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering, volume 100