Influence of Labyrinth Side Weir Shape Modification on the Hydrodynamic Performance: Experimental and Numerical Study

Abstract

Controlling water levels in main channels by constructing side weirs can be influenced by geometric modification. Therefore, proposed geometric changes to the crest of the traditional sharp-crested weir are tested to study the hydrodynamic performance of these weirs. Triangular labyrinth side weir with and without a ramp, curved wing crest and 3 different diameters of circular crest were investigated experimentally and numerically. All the tested shapes have three inclusion angles (θ = 30, 45, and 60°), and three heights (0.1, 0.15, 0.2 m). The fluid volume (VOF) and the turbulence renormalization (RNG k-ϵ) method were selected for simulation and verifying the free surface flow along the center line and beside the weir in the main channel and measuring the velocity at certain cross sectionssections. The smaller inclusion angle between the walls (θ = 30°) performs better in discharging side flow and has a higher discharge coefficient than others. Upon comparison with a traditional labyrinth side weir, a modified side weir with a curved wing and a smaller circular crest diameter increases discharge coefficient (Cd) by about 20.7% and 6.43%, respectively, while its value reduced with the increase of crest diameter and its performance decreased about 17% by increasing the weir crest diameter from 2.5 to 5 cm. However, no improvements have been visualized for adding an upstream ramp. Moreover, in a smaller inclusion angle, the diverting streamline width of flow was obtained to be 0.81 and 0.65 times the main channel width for the modified weir with a curved wing and triangular labyrinth side weir, respectively. In addition, the highest separation zone width downstream of the parent channel for inclusion angle (30°) was observed to be about 2.5 and 1.8 times its width of angle (60°) for curved wing and traditional labyrinth weir, respectively. The discharge coefficient of the curved wing was 3 times the normal rectangular side weir coefficient.