Mean velocity and turbulent characteristics of flow over half-cycle cosine sharp-crested weirs

Hydraulics of flow over full-cycle cosine and rectangular sharp-crested weirs

“…The values of both Froude and Reynolds numbers were within the range of previous studies in the literature, indicating that the experiments described here are scalable to typical practical dimensions for such weirs (Swamee et al 2001;Azimi et al 2016;Salehi et al 2019).…”

“…It was observed that the geometrical properties of full-cycle cosine weirs increased the range of transverse velocity components to negative values in comparison with rectangular weirs which all transverse velocity components are positive (i.e., towards the centerline). Similar transverse velocity patterns were also reported for sinusoidal and half-cosine sharp-crested weirs (Oreizi et al 2015;Salehi et al 2019) due to flow blockage. Near the weir wall at x = -20 mm, the maximum inward transverse velocity occurred at z/H = 0.25 and increased with the neck opening.…”

“…( 7). Figure 4b shows the variations of the proposed discharge coefficient in full-cycle cosine weirs and discharge coefficient of half-cosine sharp-crested weirs (Salehi et al 2019) In order to show the non-linearity of discharge coefficient equations with the upstream head, the variations of the rate of change of discharge coefficient with upstream head, dC D /dh o , with h o /P were calculated and the results were shown in Figure 5. The classical Rehbock formula (Ackers et al 1978) for full-width sharp-crested weirs (i.e., C D = 0.611+0.075(h o /P)) gives a constant value D r a f t of 0.075 for the derivative of discharge coefficient with upstream head.…”

“…The effects of approach flow and geometry in weirs are quantified by discharge coefficient, C d . A side from fully suppressed sharpcrested weirs, different weir geometries have been designed (i.e., rectangular, triangular, trapezoidal, half-circular, and sinusoidal cross-sections) and semi-empirical formulations were introduced to correlate discharge coefficients with geometry and approach flow conditions (Baddour 2008;Bagheri and Heidarpour 2010;Vatankhah 2010;Oreizi et al 2015;Di Stefano et al 2016;Bijankhan and Ferro 2017;Salehi et al 2019). The simplified formulation for full-width and rectangular sharp-crested weirs demonstrated a linear relationship between normalized upstream head, h o /P, and discharge coefficient, C d (Ackers et al 1978;French 1986).…”

“…A recent experimental study on performance of half-cosine weirs indicated that half-cycle cosine weirs are able to predict discharge more accurately since they are more sensitive to variations of upstream head in the neck region (Salehi et al 2019). However, a half-cosine weir behaves as an orifice if the upstream head passes the neck level.…”