Side Weir Flow Characteristics: Comparison of Piano Key, Labyrinth, and Linear Types

Side weirs are widely used to divert a part of the discharge in irrigation channels and sewer systems. To increase the discharge capacity of linear side weirs at constant length in a channel bank, the application of folded plan forms such as the labyrinth and piano key in a side configuration warrants further research. In this experimental study, nine piano key side weirs and nine rectangular labyrinth side weirs with the same crest print and three linear side weirs were investigated. Free surface flow characteristics (e.g., water surface profiles, flow pattern, and deflection angles) were studied in a subcritical regime. Using De Marchi’s model, discharge coefficients of the side weirs were estimated. Results show significantly higher discharge coefficients for the folded shape side weirs compared with the linear side weirs. Although the results indicate no significant difference in discharge coefficients between the piano key and the rectangular labyrinth side weirs, the former is the better alternative to overcome space or other construction site limitations.