Author(s): Jose M. Carrillo; Jorge Matos; Ruth Lopes; Antonio Vigueras-Rodriguez
Keywords: Labyrinth weir; Discharge capacity; Two-dimensional simulations; Iber
Abstract: It is well known that the flow over a labyrinth weir is fully tridimensional, with flow separation and non-hydrostatic pressure conditions near the weir. Its hydraulic behavior has been mainly studied in experimental models. More recently, few studies solved the three-dimensional flow behavior by using 3D computational fluid dynamics (CFD) models. However, these simulations require significant computational effort, and are time consuming when large areas need to be calculated, limiting their use in flooding simulations. In this study, the main flow characteristics of labyrinth weirs, such as the discharge capacity and the flow depths downstream of the labyrinth weir, were analyzed by using shallow water approaches, widely used in flooding modeling. Numerical results were compared with experimental data previously acquired in a relatively large-size labyrinth weir, with a 30º sidewall angle. As an example of 2D code, the free code Iber was selected. Reasonably good results were obtained for the discharge coefficient of the labyrinth weir, and for the flow depths near the downstream end of the channel reach, using the internal condition of Iber to model the weir. However, in the short vicinity of the weir, the flow depths were not accurately modeled, as expected, given the inherent limitations of the code for solving non-hydrostatic pressure regions.