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Simple Flow Measurement Structures
Published in Zohrab A. Samani, Hydraulic and Hydrologic Engineering, 2022
Critical flow can be created by contracting the cross-section of an existing canal without changing the existing canal dimensions. Simple flumes create a small section of critical flow before water returns to its previous energy state after a hydraulic jump has occurred. Minimal head loss is required and no extended inflow or outflow transition is needed. These flumes reduce the cost, calculations, and head loss while minimizing the materials needed to measure flow. As canals come in various shapes and sizes, various short-throated flumes have been developed to measure the respective flows. The three simple flume types that have been developed are circular, rectangular (S–M), and trapezoidal flumes (Figures 7.2, 7.11, and 7.20).
Hydraulic Structures
Published in David Stephenson, Water resources management, 2003
Sometimes the bed gradient is measured and if the flow can be assumed to be uniform, this is used instead of the energy gradient. Flumes may also be used for flow measurement and by constricting the width of the channel it is possible to increase the flow velocity such that the flow depth passes through critical depth. Thus, weirs and flumes work on the principle of upstream measurement and not a differential measurement of water depth. They both result in a higher flow velocity downstream than in a normal channel and as a result erosion can occur.
Open Channel Flow Measurement
Published in Michael A. Crabtree, The Concise Industrial Flow Measurement Handbook, 2019
The second class of primary devices in general use is the flume (Figure 13.6). The main disadvantage of flow metering with weirs is that the water must be dammed, which may cause changes in the inflow region. Further, weirs suffer from the effects of silt build-up on the upside stream. In contrast, a flume measures the flow in an open channel in which a specially shaped flow section restricts the channel area and/or changes the channel slope to produce an increased velocity and a change in the level of the liquid flowing through it.
Structure of open-channel flows through an array of square cylinders
Published in Urban Water Journal, 2022
Marina Oukacine, Frederique Larrarte, Nicole Goutal
The experiments were carried out in a rectangular open-channel with a length of 18 m long and a width B of 1 m (Figure 1(a,b)). The working length of the flume was Lc = 17.25 m (Figure 1(d)), and the flume bed slope in the streamwise direction, S0, equaled 1.05 × 10−3. The glass flume bottom was covered with dense synthetic grass, consisting of 1 × 10−3 m wide and 5 × 10−3 m high rigid blades (Figure 1(b)), with a density of 256 blades per square centimeter. At the downstream end of the flume, a variable tail weir enabled controlling the water surface elevation. A right-handed Cartesian coordinate system was used. The axes were aligned with the streamwise (along the flume bottom), transverse, and vertical (normal to the flume bottom) directions. The origin was defined by: x = 0 m at the end of the vertical linear ramp that raised the water level to that of the synthetic grass bed (Figure 1(b)); y = 0 m at the right-hand sidewall of the channel; and z = 0 m at the top of the rigid grass blades. Note that the right-hand sidewall is made of glass, while the left-hand sidewall is Plexiglas from x = 0 to 16.5 m and then steel from 16.5 to 17.5 m (i.e. an initially vertical splitter plate (Figure 1(a)). In the channel, the water circulates in a closed circuit and the flow is controlled by a Krohne electromagnetic flowmeter.
Experimental study of fish-friendly angled bar racks with horizontal bars
Published in Journal of Hydraulic Research, 2022
Fatma Lemkecher, Ludovic Chatellier, Dominique Courret, Laurent David
The experiments were conducted in a 1 m wide, 1 m deep and 12 m long open channel at the Institut Pprime, with a PVC bed and glass side walls (Fig. 1). A weir at the outlet of the flume serves to adjust the water head. The flow rate (Q) of 1800 m3 h−1 (0.5 m3 s−1) and the water depth (H1) of 0.7 m were maintained for an approach velocity (V1) of 0.72 m s−1 after investigating two discharges of 0.375 and 0.5 m3 s−1 to verify the invariance with respect to the Reynolds and Froude numbers. According to previous studies (Albayrak et al., 2018; Raynal et al., 2013a), the head loss coefficient is invariable for a Reynolds number higher than 3000 and for a Froude number F higher than 0.1. In our experiments, the Froude number was about 0.275 and the bar-Reynolds number () was 3600 for the flow rate of 0.5 m3 s−1.
Experimental study of the energy dissipation on rough ramps
Published in ISH Journal of Hydraulic Engineering, 2021
Akram Abbaspour, Pardis Shiravani, Ali Hosseinzadeh Dalir
The experiments were conducted in a metal-glass flume with a rectangular section. The flume was 0.25 m in width and 0.5 m in depth. The channel slope was 0.002 and 10 m in length. The rectangular ramps were 0.25 m in width (W) and 0.5 m in length (L) with three slopes at the angles (S) of 15, 22.5 and 30-degree. A broad crested weir (L = 0.25 m) was placed on the ramps upstream. The ramps heights were 0.13, 0.19 and 0.25 m. The water depths over weir (y0) and at the ramp downstream (the initial and second depths of jump y1 and y2) were continuously measured using ultrasonic sensors and data was recorded on a computer and processed by VisiDAQ. Then, the mean water depth (y0, y1, and y2) was calculated. The flume was equipped with a triangular weir placed at the flume end. The discharge-head relationship (Q-h) for the triangular weir was Q = 0.6918h2.5 in experiments. The base material roughness was made of natural stones with a mean diameter of 4.3 mm. Ten ramps with different arrangements, namely row (A, B), zigzag (C), V shape (D), scatter (E) and rowed (a, b), zigzag (c), V shape (d), scatter (e), were used in this study (Figure 1). The roughness rows (d) spaced 5D50 in all arrangements. The plan and section of the experimental setup are shown in Figure 2.