Investigating a new approach to enhance the discharge capacity of labyrinth weirs

Abstract

Climate change has caused the inefficient operation of a significant number of old weirs to pass large discharges. Therefore, this study aims to increase the discharge capacity of the labyrinth weir. A new approach was proposed by modifying a labyrinth weir structure. The data was obtained from the quarter-round crest and different sidewall angles ranging from 8 to 35°. A conventional labyrinth weir was used for comparison. The results showed that the percentage of the notches area to sidewalls area of the weir (An/Aw) does not exceed 8%. Also, the percentage of the notches' length to total crest length (ΔL/Lc) does not exceed 32%. Also, the percentage of the notch depth to the sidewall depth (ΔP/P) does not exceed 30%. The other parameters are kept constant. These dimensionless terms provided a maximum compound coefficient of discharge of 0.74. Also, the compound discharge coefficient initially increased at low water head ratios and decreased at higher values of water head ratios. The regression empirical equations were generated. The maximum increase in efficiency was 10% for a sidewall angle of 6° when compared to conventional labyrinth weirs. The maximum improvement of the compound coefficient of discharge was 18.8% for a sidewall angle of 8°. HIGHLIGHTS A new approach to the labyrinth weir was proposed and named compound labyrinth weir to improve the discharge capacity of the labyrinth weir.; Derivation of hydraulic equation for compound labyrinth weir has been done.; Establishing the set of curves showing the relationship between the compound coefficient of discharge Cdc against total head over the entire compound labyrinth weir H′t/P′ with a range of sidewall angles.; Empirical equations for compound labyrinth weir and compound linear weir were created.; Using the compound labyrinth weir efficiency (έ) as a new tool to provide a guide in choosing a suitable design of the sidewall angle (α).;

Keywords

• a quarter-round crest
• compound labyrinth weirs
• cycle efficiency
• head–discharge relationships
• nappe flow conditions