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Measurement of Irrigation Water
Published in A. Zaman, Md. Hedayetullah, Sustainable Water Resource Development and Management, 2022
Rectangular weirs are easy to construct and convenient to use. The disadvantages of weirs are that they require a considerable loss of head which may not be available on ditches with a flat grade attachment. The weir pond causes deposition of silt from those streams carrying a heavy silt load or mud and these deposits in the channel of approach destroy the proper conditions for weir measurements. These weirs should not be combined with headgate structures of the device for accurate measuring.
Dimensional Analysis and Dynamic Similitude
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
A weir is an obstruction placed in the flow of a liquid in an open channel. The liquid height upstream of the weir can be used to determine the volume flow rate over the weir. Assuming that the volume flow Q is a function of upstream height h, gravity g, and channel width b, develop an expression for Q by using dimensional analysis.
Runoff and Rainwater Harvesting
Published in Abrar Yousuf, Manmohanjit Singh, Watershed Hydrology, Management and Modeling, 2019
Junaid N Khan, Rohitashw Kumar, Abrar Yousuf
A weir is a barrier across a river designed to alter the flow characteristics. In most cases, weirs take the form of a barrier, smaller than most conventional dams, across a river that causes water to pool behind the structure and allows water to flow over the top. Weirs are commonly used to alter the flow regime of the river, prevent flooding, measure discharge and help render a river navigable (Arora 1980). Weirs are structures consisting of an obstruction across the open channel with a specially shaped opening or notch. The weir results in increase in the water level, or head, which is measured upstream of the structure. The flow rate over a weir is a function of the head on the weir.
Estimation and comparison of gabion weir oxygen mass transfer by ensemble learnings of bagging, boosting, and stacking algorithms
Published in ISH Journal of Hydraulic Engineering, 2023
KM Luxmi, N. K Tiwari, S Ranjan
A fluidic structure put across the river flow to change its hydraulic characteristics is called a weir. Usually, impermeable weirs are constructed from concrete, metal, rubber, brick, etc., and used for various engineering purposes. However, alternative weirs made of porous media, popularly called gabion weirs, are preferred because they fulfill natural, economic, and ecological requirements (Mohamed 2010). They are manufactured using locally available porous particles packed with distinct shapes and sizes of coarser materials. They divert water flow for domestic use, irrigation, and industrial requirements. Another advantage of the gabion weirs is that they offer a meager cost as their construction is simple and skilled labor is unnecessary. Oxygen mass transfer over cascades and weirs was the interest of numerous investigators (Nakasone 1987; Avery Sean and Novak 1978; Wilhelms et al. 1993; Chanson 2000). Oxygen mass transfer at rectangular and triangular labyrinth weirs was studied by Wormleaton and Soufiani (1998). Hoque and Paul (2022) investigated oxygen mass transfer experimentally and discussed the penetration depth of the air bubbles. Park and Yang (2019) experimented with estimation of oxygen transfer at vertical-up.
Experimental and numerical analysis of flow hydraulics in triangular and rectangular piano key weirs
Published in Water Science, 2020
Rezvan Ghanbari, Mohammad Heidarnejad
A weir is a structure used to avoid excessive storage of water in the reservoir and transfer the excess water, especially during the flood times, from upstream to the downstream areas and rivers. Weirs are one of the main and important structures of a dam. Considering their sensitive role, the weirs are required to be readily operational for utilization and discharge of the floodwaters and protection of the dam and the associated installations (Beyrami, 1997). Hydraulic efficiency of the free over-fall weirs for a given head is directly related to the length of the weir, and the discharge coefficient (Cd) of this type of weirs can be calculated using Equation (1) (Henderson, 1966).
Estimation of rectangular and triangular side weir discharge
Published in ISH Journal of Hydraulic Engineering, 2023
Saeed Balahang, Masoud Ghodsian
Side weirs are widely used to divert the excess flow of the main channel to the side channel. Side weirs are of different types (sharp-crested and broad-crested) and different shapes (rectangular, triangular, semicircular, and trapezoidal). Figure 1 shows the subcritical flow along a rectangular and a triangular side weirs. Here Q1 is the upstream discharge, Q2 is the downstream discharge, y1 is the upstream depth of flow, y2 is the downstream depth of flow, p is the height of weir, L is the side weir length, and θ is the apex angle of triangular side weir.