Discharge Coefficient of Rectangular Short-Crested Weir with Varying Slope Coefficients

Abstract

Rectangular short-crested weirs are widely used for simple structure and high discharge capacity. As one of the most important and influential factors of discharge capacity, side slope can improve the hydraulic characteristics of weirs at special conditions. In order to systemically study the effects of upstream and downstream slope coefficients S 1 and S 2 on overflow discharge coefficient in a rectangular short-crested weir the Volume of Fluid (VOF) method and the Renormalization Group (RNG) κ-ε turbulence model are used. In this study, the slope coefficient ranges from V to 3H:1V and each model corresponds to five total energy heads of H 0 ranging from 8.0 to 24.0 cm. Comparisons of discharge coefficients and free surface profiles between simulated and laboratory results display a good agreement. The simulated results show that the difference of discharge coefficients will decrease with upstream slopes and increase with downstream slopes as H 0 increases. For a given H 0 , the discharge coefficient has a convex parabolic relation with S 1 and a piecewise linearity relation with S 2 . The maximum discharge coefficient is always obtained at S 2 = 0.8. There exists a difference between upstream and downstream slope coefficients in the influence range of free surface curvatures. Furthermore, a proposed discharge coefficient equation by nonlinear regression is a function of upstream and downstream slope coefficients.

Improvement of Scientific Approaches to the Development of Engineering

“…Numerical simulations were performed using the COMSOL Multiphysics simulation software. Its two-phase solver, which is based on the volume of fluid (VOF) method, has been proven to successfully model complex flows [51][52][53].…”

Hydraulic analysis of a compound weir (triangular-rectangular) simulated with computational fluid dynamics (CFD)

“…Bautista et al (2013) used a low-speed photographic technique to characterize the upper and lower profiles of the flow draft on a triangular weir. Chen, Fu, Chen, and Cui (2018) analyzed the effects on the discharge coefficient by the variation of the slope of the ramps implemented on the upstream and downstream faces in a rectangular short-crest weir. Fu, Cui, Dai, and Chen (2018) proposed an equation to determine the discharge coefficient in structures of the orifice -weir type.…”

Numerical Modeling of Flow Over a Rectangular Broad-Crested Weir with a Sloped Upstream Face

“…Figure 3 compares numerical and experimental free-surface profiles for three typical broad-crested weir configurations (θ = 10 • , 45 • and 90 • ). Chen et al [37] divide the free-surface profile into two parts based on the gradient: a slowly descending part and a sharply descending part. The curvature of the former part is close to zero, whereas that of the latter part decreases quickly with a hydraulic drop.…”