Subcritical Flow at Open Channel Structures - Open Channel Expansions

摘要

Analyzing the hydraulics of open channel constrictions was modified to allow the analysis of energy loss in open channel expansions. The modified subcritical flow technique was compared with previous methods of analysis using data collected in the laboratory on open channel expansions with vertical walls, and triangular-shaped baffles. Also, a design procedure for such baffled outlet structures was developed. The expansion ratio has a significant influence upon the hydraulic characteristics of open channel expansions. As the expansion ratio is increased, the degree of nonuniformity of velocity distributions in the expansion structure will increase with consequent increases in energy loss. Any flow instability at the inlet will become more aggravated as the flow moves through the expansion. Thus, the flow at the outlet will be improved if uniform flow with uniform velocity distribution and hydrostatic pressure distribution occurs at the inlet. Although such ideal flow conditions cannot usually be expected under field conditions, they can serve as a goal for the hydraulic engineer. (WRSIC abstract)