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This paper presents experimental work to investigate the discharge coefficient for a compound V-notch weir. This weir is composed of two triangular parts with distinctive notch angles. Fundamental standards were utilized to connect the release to the significant geometrical and hydraulic parameters in non-dimensional form. Physical model tool was u...
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Thin-plate weirs are the simplest and least expensive devices, which frequently have been employed in many water projects. In this research, a unique type of Sharp-Crested V-notch weir, entitled SCVW, has been introduced. The hydraulic characteristics of the present weir were investigated theoretically and experimentally under free aerated flow con...
Citations
... Water supply, wastewater, and sewage systems rely on different types of notches. The ratio of actual discharge to theoretical discharge provided by the structure is known as the coefficient of discharge ( [17]; Mohammed, 2017 [18]; Hossieni et al., 2018; [19]). Lot of researches has been carried out to determine the hydraulic coefficients of different materials under different bed slopes and bed materials [20][21][22][23], but there are uncertainties regarding the influence of bottom slope, bed particle size, under various bed configuration and hydraulic coefficients, influence of particle shape on open channel flow and influence of bed slope on discharge, as well as the influence of roughness coefficient on discharge, Froude and Reynolds numbers, and the value of hydraulic coefficients in different bed materials under different channel slopes and bed configurations. ...
... When the bed configuration was adjusted from random to perpendicular to the flow bed pattern with and without weir, both the roughness coefficient and discharge dropped [26]. The coefficient of roughness was increased when the channel bed contains high roughness material [18]. Experiments conducted on a steeper channel slope (1:200) investigated the relationship between the bed roughness and the roughness coefficient. ...
... The Manning's roughness coefficient represents the energy loss due to the water friction against bed surface roughness and this roughness in bed surface increases the flow in the channel and flow velocity is strongly dependent on the resistance to flow (Mohammed, 2017; [18]). As the value of the Manning's roughness coefficient (n) increases, the velocity of the water flowing across the surface decreases. ...
... The results and data presented by these, and other authors were followed by comprehensive works describing flow over TPWs with a triangular notch: Shen (1981), Bos (1989), Hager (1990), and the ISO 1438 (2017) standard. Currently, research on triangular notch TPWs focuses on the geometry of the approach channel (Hattab et al., 2019), the shape of the notch (Ali et al. 2015;Martínez et al., 2005;Piratheepan et al., 2007), new approaches to determining the discharge coefficient (Bautista-Capetillo et al., 2013;Chanson and Wang, 2013) and extending the applicability of such approaches to include small notch angles and small discharges (Pospíšilík and Zachoval, 2023). ...
The article deals with the determination of the influence of the relative width of an approach channel with a rectangular cross-section on the discharge of clean water flowing over thin-plated weirs with a triangular notch and zero height of the weir above the bottom of the approach channel. To evaluate the influence, the Kindsvater-Shen equation was modified by introducing the basic effective discharge coefficient and the coefficient of the relative width of the approach channel. The coefficient of the relative width of the approach channel was determined based on the evaluation of data from three extensive experimental research investigations. It is valid for the entire possible range of relative widths of the approach channel and for the range of notch angles from 5.25° to 91.17°. The relative error of discharge determination is approximately up to ±2% over the entire range of discharges used in the conducted experimental research. The evaluation made it possible to determine the boundary distinguishing the partially contracted weirs from the fully contracted weirs in terms of impact on discharge.
... Ghodsian (2004) obtained a new relationship for the calculation of coefficient of discharge. Martínez et al. (2005), Piratheepan et al. (2007) and Ali et al. (2015) investigated composite TPWs with a triangular notch. Ji (2007) and Ramamurthy et al. (2013) experimentally investigated TPWs with several triangular notches. ...
The paper deals with the determination of the discharge coefficient, effective head and newly the limit head in the Kindsvater-Shen formula for the determination of a relatively small discharge of clear water using a thin-plate weir with a triangular notch. The determination of the discharge coefficient, effective head and limit head is based on extensive experimental research and is verified by previous measurements by other authors. The experimental research was characterised by a large range of notch angles (from 5.25° to 91.17°), weir heights (from 0.00 m to 0.20 m), and water temperatures (from 15 °C to 45 °C), as well as a focus on relatively small heads (from 0.02 m to 0.18 m), which is where the strengths of the Kindsvater-Shen formula stand out. The experimental research supplemented existing knowledge about the overflow occurring with small heads and small weir notch angles. The newly determined dependencies in the Kindsvater-Shen formula extended its applicability to weirs with small notch angles and newly enabled the determination of the limit head, which restricts its applicability in the determination of small discharges.
ABSTRACT
Assessment of irrigation performances is very essential in taking different water management strategies. However, the performance of Tahtay Tsalit and Mychew irrigation schemes were not assessed yet and hence, this research was undertaken to investigate and compare the performance of the two small-scale irrigation schemes. Moreover, identification of the cause and effect for malfunctionality of irrigation structures was also another objective of this study. Hence, comprehensive field observations and focus group discussions was held to investigate the cause and effect of failed hydraulic structures. Moreover, field measurements on canal dimensions and water flow measurements were undertaken at selected sampling points. Simple descriptive statistics was employed for analysis of the data collected from group discussions and observations. However, hydraulic performance indicators were used to evaluate the performance of the two irrigation schemes. Several factors such as flooding, sedimentation, design problem, damage of sluice gates, abstraction of irrigation water by unwanted plants has been identified in both schemes for malfunctionality of different structures. There was no any problem in irrigation adequacy, equity, dependability and efficiency of irrigation water in Tahtay Tsalit irrigation schemes. However in Mychew, the adequacy (0.75) and equity (0.28) of irrigation water was categorized as poor, while good and fair for dependability (0.08) and irrigation efficiency (0.79) respectively. For both irrigation schemes, the average water surface elevation ratio, delivery performance ratio, and delivery duration ratio of the main canal during the monitoring period was less than one, greater than 5% , and 150% respectively. The highest sediment accumulation was observed at head and middle reaches of the irrigation schemes than the tail reaches for both irrigation schemes. Generally, in both irrigation schemes there were a number of irrigation structures which were malfunctioned. Now needs sustainable solution to improve the performance of the irrigation schemes. Hence, it was recommended that Water should be fairly distributed spatially and temporally particularly at Mychew irrigation scheme. Moreover, capacity building and awareness creation to concerned bodies holds the key to bring a difference in irrigation water management in both irrigation schemes.
Key words: hydraulic performance, Comparative analysis, Small scale irrigation schemes
