Influence of Channel Width on Flow Distribution in Four-Branch Junctions with Supercritical Flow: Experimental Approach

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An experimental study of the supercritical dividing flow in a right-angle, four-branch junction with different channel widths is presented. Lateral-to-mainstream width ratios of 1∶1, 2∶3, and 1∶2 were used to establish the influence of the channel width on the flow distribution. A brief description of the flow characteristics is given. Types I and II flow patterns are confirmed by the experiments in the range of the studied variables. Existing flow distribution models were adapted for width ratios other than 1∶1 and tested for Type II, subregime 3 flow pattern, finding poor results. Other existing flow distribution models for Type II, subregimes 1 and 2 flow pattern and a width ratio of 1∶1 give a very good fit with the experimental data. A new flow distribution model for Type II, subregimes 1 and 2 flow pattern and width ratios of 2∶3 and 1∶2 was proposed, which is a function of the Froude number and the width ratio. A former model for predicting the flow distribution in equal-width (1∶1 width ratio) junctions was extended for width ratios of 2∶3 and 1∶2. This model expresses the flow distribution as a function of the inflow power ratio and has the advantage over existing models that, for its application, the flow structure (angles of the oblique jumps) in the junction does not need to be determined beforehand. Although it is not necessary to apply the proposed flow distribution model, the flow structure (flow type and angle of the oblique jump or jumps, if presented) can also be predicted through the inflow power ratio, the inflow ratio, and the channel slope combination in the case of width ratios of 2∶3 and 1∶2.