Cross-Beam Dissipators in Abruptly Expanding Channels: Experimental Analysis of Flow Patterns

Cross-section expansion can be a convenient solution to enhance the performance of stilling basins. However, under certain working conditions, the undesired phenomenon of flow instability can result in asymmetric flow with less efficient dissipation and high local velocity concentrations in the tailwater channel. This paper presents an experimental investigation on a recently proposed dissipator consisting of a series of cross beams, tested in various geometric configurations and under different hydraulic conditions. The effectiveness of the device is first analyzed in terms of flow uniformity and velocity in the channel bed while also providing a theoretical explanation of the observed dissipative mechanisms. Furthermore, in a second phase, the performance of the system is tested under variable tailwater conditions, with the description of the three-dimensional flow patterns observed in the downstream channel. The results suggest that the installation of this type of dissipator allows for the benefits of cross-section expansion while avoiding its damaging effects.