Estimation of Discharge in Straight Compound Channels Based on The Equivalent Roughness Using The Particle Swarm Optimization Algorithm

Several relations have been presented to estimate the flow discharge passing the straight compound channels, most of which result in acceptable results in the experimental conditions, but are not accurate enough to be sued in the case of the field studies. In the present study, the Particle Swarm Optimization Algorithm was used to analyze the experimental and field data of the compound cross sections and a new relation was presented to estimate the total discharge passing the compound cross section. In the new suggested relation, in order to estimate the equivalent roughness coefficient of the compound cross sections, in addition to the relative depth, relative width, relative hydraulic radius and relative roughness (the ratio of the mentioned parameters in the floodplains to the main cross section), a new definition of the Reynolds number was used. The results showed that the proposed relation, with an average absolute relative error of 10.4, could properly estimate the discharge in the compound cross sections so that the average absolute relative error decreased by about 38 percent in comparison to the previous studies performed by other researchers.