The Hydraulic Investigation of Harmonic Plan Weirs

Abstract

Existing dams and reservoirs need to be revised to meet safety standards. For the existing reservoirs where flood control is important and the maximum water level is limited, the best method to increase reservoir capacity is to build a labyrinth weir on the dam. In labyrinth weirs, the collision of two nappe flows produces nappe inter-ference, and this reduces the weir performance. In this study, the semi-circle weirs are placed in an open channel harmonically to increase the efficiency of the labyrinth weirs to make the areas more efficient and increase the flow capacity because of the nappe interference and to ensure the flow moving perpendicular to the weir as possible. In the experimental study of the asymmetrically placed circular weirs, 3 different weir heights (P = 20 cm, 30 cm and 40 cm) and 3 different labyrinth cycle numbers (N = 2, N = 3 and N = 4) were used. As a result of the experiments, although there was a 13 % decrease in the discharge coefficients (Cd) compared to the linear weirs, it provided a 57 % increase in the net crest length (Lnet). Discharge coefficient (Cd) is decreased 3.4 %, as the number of cycles (N) increases. As the weir height (P) decreases, Cd increases 7.5 % due to the vacuum effect.