Experimental and numerical investigation of rectangular Labyrinth weirs in open channel

Labyrinth weirs are commonly used hydraulic structures to increase discharge efficiency in free-overflow discharges. These weirs provide higher discharge efficiency than conventional linear weirs at the same headwaters. This study investigated hydraulic performance of rectangular labyrinth weirs under different geometries and flow conditions experimentally and numerically. The numerical model was verified and validated using the grid convergence index method recommended in the literature and the experimental data. The numerical modelling results showed that the increase in performance of the labyrinth weir was caused by the distribution of lateral velocities in the inlet keys, while the nappe interference in the downstream keys was responsible for the decrease in performance at high headwater. Within the limitations of 1.5≤L/B≤2.33 and 0.1<H_o/P<0.61, a performance increase of 44% on average and a maximum of 67% for unit channel width was found for rectangular labyrinth weirs compared to linear weirs. For given limitations, two new empirical formulas with high correlation were derived to estimate the discharge coefficients of rectangular labyrinth weirs based on channel width (B) and weir crest length (L) for H_o/P>0.1 in which are widely used in practice. It is concluded that, when compared with some of the data in the literature, the empirical formulas give satisfactory results.