HYDRAULIC PERFORMANCE ANALYSIS OF DIAGONALLY ALIGNED CIRCULAR LABYRINTH WEIRS USING COMPUTATIONAL FLUID DYNAMICS

Abstract

Weirs are among the most critical hydraulic structures employed for the con-trolled conveyance of water in open channel systems. In conventional free over-flow weirs, the discharge capacity is predominantly a function of the upstream head. However, for operational efficiency and stability, it is often undesirable for the upstream water level to vary significantly with changes in flow rate. To over-come this limitation, labyrinth weirs—particularly sharpcrested types—have gained prominence in recent years due to their ability to increase the effective crest length within a limited channel width. The extended crest length enhances the discharge capacity at a given head, making labyrinth weirs more efficient than linear-crested weirs. Over the years, various labyrinth weir geometries, including trapezoidal, triangular, and piano key configurations, have been explored to improve hydraulic performance. Recently, new forms such as circular and diagonally stepped labyrinth weirs have been introduced. Circular labyrinth weirs offer improved discharge efficiency by minimizing nappe interference and reducing submergence at the weir cycles. On the other hand, diagonally stepped labyrinth weirs aim to enhance flow capacity at a constant head and crest length through steep downstream alignments. This study combines on the hydraulic performance of circular and diagonal stepped labyrinth weirs. Numerical model validation was conducted based on established findings from previous studies. Utilizing these validated models, a novel nappe breaker configuration was introduced and the discharge performance of stepped circular labyrinth weirs was comparatively assessed in plan view.