Abstract
Application of side weirs with high effective length is necessary to discharge excessive flows, to control the flow in water conveyance systems, and irrigation and drainage systems. Most of the studies on the side weirs have been conducted on the straight channels and linear weirs. The flow pattern on the outer arc of the curved channels and its suitability for side weir can be used and combined with the piano key weirs. So far, no comparison has been made on rectangular piano key side weirs (RPKSW) at a 120° Section of a 180° Curved Channel. In this study, an experimental study was performed on A-, B-, C-, and D-type RPKSW at a bend angle of 120 degrees. The results showed that the specific energy at two ends of the RPKSWs was the same, with a slight difference of 3.4% for A-Type, 1.3% for B-Type, 1.1% for C-Type, and 1.8% for D-Type weirs. The discharge coefficients of the studied weirs were also investigated, and it was concluded that B-Type weir has better performance than other weirs. On average, the discharge coefficient of B-Type weir was 9.9%, 21.2%, and 24.1% higher than that of A-Type, C-Type, and D-Type weir, respectively. It was shown that the ratio of P/h1 is the main parameter affecting the weir discharge coefficient. Finally, an empirical equation was proposed for each weir. The proposed equation has MAE = 0.028 for A-Type weir, MAE = 0.041 for B-Type weir, MAE = 0.049 for C-Type weir, and MAE = 0.053 for D-Type weir.
Highlights
Weirs are typically designed and constructed in two general ways: perpendicular or parallel to the flow direction
Rectangular piano key weirs (RPKW) in the straight channels as inline weir were first investigated by Blanc and Lempérière (Erpicum et al 2013)
The results of this study can be summarized as follows: Specific energy for the curved channel is stable at an angle of 120 degrees with a nonlinear side weir, and the difference in E1 and E2 is negligible in this study
Summary
Weirs are typically designed and constructed in two general ways: perpendicular (inline) or parallel (lateral) to the flow direction. Piano key weir (PKW) is nonlinear weirs that have better benefits than the other weirs due to position, discharge capacity, and the upstream head of the weir (Li et al 2020) These weirs usually are located perpendicular to the flow direction. Anderson and Tullis (2012) investigated experimentally inline RPKW and labyrinth weir They indicated that the RPKW discharge coefficient at a straight channel (inline) was greater than that of the labyrinth weirs. Kumar et al (2020) studied the trapezoidal piano key weir (TPKW) and evaluated the discharge equation of these weirs They developed an equation using the M5 intelligent method for determining the discharge coefficient
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