Transcritical Flows in Three and Four Branch Open-Channel Intersections

Abstract

Transcritical flows in three and four branch channel intersections have been studied experimentally, and an empirical relationship is derived from the data to express the flow distribution as a function of the Froude number of the flow in the main channel downstream of the intersection, and in the case of the four-branch intersection, the ratio of the incoming flows in the two inlet channels. The empirical relationship agrees closely with the data from this study, and with data from other studies in comparable conditions. The results illustrate an important point which has been overlooked in some previous studies—the existence of a critical section in the lateral outflow channel is not sufficient to isolate flow in the intersection from the downstream control in the lateral channel. It is shown that if drowned flow occurs in the lateral channel, then the downstream control can affect the flow in the intersection.