VELOCITY DISTRIBUTION INSIDE AND ABOVE BRANCHED FLEXIBLE ROUGHNESS

The purpose of this study is to develop function relationships for the velocity distribution of water flow in and above a model of branched grass. A trapezoidal cross-section flume is constructed for this study, and branched plastic strips are used to simulate the grass in nature. A correct determination of flow characteristics for channels suffering from submerged weeds is desirable. Furthermore, knowledge of the changes of velocity distribution as a result of the presence of weeds and the changes in the shear stress at the bed will improve understanding of the different problems associated with this type of channel. Power- and logarithmic-function relationships are developed to describe the velocity distribution of water inside and above branched flexible-roughness elements (which represent the submerged weeds) in trapezoidal open channels. An experimental study was carried out in the hydraulic lab at Cairo University, Cairo, Egypt, to check the validity of the prediction equations that relate the velocity distribution to the depth of water in the channel cross section. More than 170 velocity profiles have been measured at different locations along the channel length and its cross sections.