抄録
For irrigation open channels with gradually width-contracted part, we aimed to evaluate the effects of changes in structure of the contracted part on the coefficient fqc of conversion loss based on laboratory experiments. The experimental results showed that fqc increased corresponding to the increase in the reduction-angle θ at the contracted part from 12.5° to 90°. Additionally, fqc decreased when the reduction-ratio B2/B1 of the downstream to the upstream channel width at the contracted part increased from 0.5 to 0.7. We conclude that the optimum value of fqc is 0.1 for designing the irrigation open channels with B2/B1 greater than 0.7. These findings are useful for determining the value of fqc for channel repairs, especially in facilities management project.
