A system of cross-beams as energy dissipater in expanding channels

Several studies have demonstrated that in abruptly expanding channels flow asymmetry phenomena can arise for certain tailwater depths. These undesired conditions are characterized by high velocity concentrations and backward flows in the tailwater channel. Based on the description of the main features of hydraulic jumps in expanding channels, this paper presents the results of an experimental investigation carried out to study the effects of a system of cross-beams in improving flow patterns in the tailwater channel. Four different beam spacings, two beam orientations and slopes, two locations and two beam heights were tested in order to define the most adequate geometry of the dissipater. Downstream flow characteristics, velocity distribution and stability under variable tailwater conditions were considered for analyzing the performances of the system. It was found that, for almost all tested configurations, the presence of the cross-beams induced a significant improvement in the flow field in the tailwater channel.