Combining Open Channel Flow at Right Angled Junctions

Abstract

In combining open channel flow, the rise in the upstream flow depth due to the effect of lateral inflow from the branch channel can be significant. For right‐angled, sharp‐edged junctions of rectangular channels, a relation between the depth of flow at the junction and the ratio of the lateral discharge to the total discharge is derived on the basis of the momentum principle. Using this relationship, one can predict the rise in the flow depth when the undisturbed flow conditions in the channels are specified. In the proposed model, the contribution of the momentum transfer from the branch channel to the main channel is included, as this factor can be significant when the lateral discharge is relatively large. The proposed relationship is verified with the results of experiments related to combining flows for which the flow conditions downstream of the junction are both critical and unsubmerged. The study of combining flow at right angle junctions has a direct application in drainage network systems and river engineering.