Discharge coefficient of a semi-elliptical side weir in subcritical flow

A labyrinth weir is an overflow weir, folded in plan view to provide a longer total effective length for a given overall weir width. The total length of the labyrinth weir is typically three to five times the weir width. In this study, a semi-elliptical labyrinth weir was used as a side weir structure. Rectangular side weirs have attracted considerable research interest. The same, however, is not true for labyrinth side weirs. The present study investigated the hydraulic effects of semi-elliptical side weirs in order to increase their discharge capacity. To estimate the outflow over a semi-elliptical side weir, the discharge coefficient in the side weir equation needs to be determined. A comprehensive laboratory study including 677 tests was conducted to determine the discharge coefficient of the semi-elliptical side weir. The results were analyzed to find the influence of the dimensionless weir length L/BL/B, the dimensionless effective length L/ℓL/ℓ, the dimensionless weir height p/h1p/h1, the dimensionless ellipse radius b/ab/a, and upstream Froude number F1 on the discharge coefficient. It was found that the discharge coefficient of semi-elliptical side weirs is higher than that of classical side weirs. Additionally, a reliable equation for calculating the discharge coefficient of semi-elliptical side weirs is presented.

A labyrinth weir is an overflow weir, folded in plan view to provide a longer total effective length for a given overall weir width. The present study investigated the hydraulic effects of semi-elliptical side weirs in order to increase their discharge capacity. A comprehensive laboratory study including 677 tests was conducted to determine the discharge coefficient of the semi-elliptical side weir. A reliable equation for calculating the discharge coefficient of semi-elliptical side weirs is presented. Figure optionsDownload as PowerPoint slideResearch highlights
► Discharge coefficient of semi-elliptical side weir is higher than that of rectangular side weir.
► Discharge coefficient of side weir tested is lower than that of triangular labyrinth side weir.
► The discharge coefficient increases with increasing dimensionless weir length.
► The proposed equation was shown to be reliable for subcritical flow conditions.
► The intensity of the secondary flow is more dominant when the weir is a labyrinth type.