Comprehensive Open‐Channel Expansion Transition Design

Open‐channel transitions involving an expansion of width are a common feature of canals and flumes. Subcritical flow through an expansion transition can result in significant head loss due to separation of flow and subsequent eddy formation. In addition to more power generation in the case of power channels and increased service area for irrigation canals, the reduction of head loss is desirable from the viewpoint of increasing the life of the transition structure. This paper discusses a methodology based on optimal control theory for designing expansion transitions for gradually varied subcritical flow. Based on a large number of expansion transition designs, usable equations have been obtained for bed‐width, side‐slope, and bed profiles.