Abstract
Side weirs are important structural measures extensively used, for instance, for regulating water levels in rivers and canals. If the length of the opening is limited, the amount of water diverted out of the channel and the effective length can be increased by applying a labyrinth side weir. The present study deals with numerical simulations regarding the hydraulic performance of a labyrinth side weir with a triangular plan in single-cycle mode. Specifically, six different types of antivortexes embedded inside it and in various hydraulic conditions at different Froude numbers are analyzed. The antivortexes are studied using two groups, permeable and impermeable, with three different heights: 0.5 P, 0.75 P, and 1 P (P: Weir height). The comparison of the simulated water surface profiles with laboratory results shows that the numerical model is able to capture the flow characteristics on the labyrinth side weir. The use of an antivortex in a triangular labyrinth side weir reduces the secondary flows due to the interaction with the transverse vortexes of the vertical axis and increases the discharge capacity by 11%. Antivortexes in a permeable state outperform those in an impermeable state; the discharge coefficient in the permeable state increases up to 3% with respect to the impermeable state. Finally, based on an examination of the best type of antivortex, taking into account shape, permeability, and height, the discharge coefficient increases to 13.4% compared to a conventional labyrinth side weir.
Highlights
Side weirs are hydraulic structures often used for flow diversion and measurement, for irrigation and drainage purposes, and control of the floods
The results showed that the discharge coefficient decreases as the Froude number increases, and the best side weirs had an angle of 30 degrees
The results showed that the increase in the crest length and the use of antivortex structures lead to an increase in the discharge capacity of trapezoidal labyrinth side weirs
Summary
Side weirs are hydraulic structures often used for flow diversion and measurement, for irrigation and drainage purposes, and control of the floods. One of the effective solutions to increase the efficiency of such structures is the use of a labyrinth side weir, changing the geometry of the plan and increasing the length of the weir when the crest of the side weir is not straight in a plane form. Assuming energy conservation in the main channel, irrespective of the friction and channel slopes, the general equation of the variable spatial flow with discharge reduction can be written as follows: dQ.
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