Variations and correlation of roughness indices of noni-vertical non-rigid fully submerged vegetation in open channels

摘要

This study presents the results of an experimental investigation on the effect of fully submerged non-vertical non-rigid cylindrical vegetation on the roughness indices in open channels. The considered roughness indices are the friction factor f, the Chezy's roughness coefficient C, and the Manning's roughness coefficient n. Six model were tested using three different channel bottom slopes. The vegetation elements were distributed in staggered way in four of them and in parallel way in the other two. It was found that the trend of variation of the roughness indices with the Froude number are similar regardless of the distribution pattern. The values of the roughness indices were found to be a function of Froude number F_n, the channel bottom slope S, and the roughness density I. Statistical prediction models were developed to estimate the roughness indices in terms F_n, S and I using the multiple linear regression analysis. Good agreement were obtained between predictions of the developed models and the measured values.