scholarly journals Analysis of various parameters affecting weir design and fabrication of Weirs: An Overview

2018 ◽  
Vol 144 ◽  
pp. 01006
Author(s):  
B. Rao Vanishree ◽  
R. Manjula
Keyword(s):  
South Africa ◽  
Structural Stability ◽  
Discharge Capacity ◽  
Geometric Parameters ◽  
Space Requirement ◽  
Labyrinth Weir ◽  
Footprint Area ◽  
Discharge Efficiency

Several geometric parameters influence weir discharge and it is explained in our present study. The PK weir is more efficient than rectangular labyrinth weir due to reduction in entrance losses of PK weir inlet key geometry. PK weir is a type of labyrinth weir with variation in angle. Therefore, in this paper we also discuss about labyrinth weir. PKW are compatible for constructing on existing or new spillway with lesser space requirement and structural stability. PKW are installed in order to increase the discharge capacity for a given footprint area. PKW is used to increase the overflow capacity of existing dams such as, Hazelmare dam (South Africa), Dartmouth dam (Australia). Trapezoidal piano key weirs have higher discharge efficiency than rectangular weirs and it is due to interference wedge. Cd of TPKW is influenced by L/W but Wi/Wo has least effect.

Performance of rectangular labyrinth weir- an experimental and numerical study

2022 ◽  
Author(s):  
Mosbah Ben Said ◽  
Ahmed Ouamane
Keyword(s):  
Discharge Capacity ◽  
Numerical Study ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Experimental Models ◽  
Absolute Relative Error ◽  
Labyrinth Weir ◽  
Specific Discharge ◽  
Labyrinth Weirs ◽  
Good Agreement

Abstract Labyrinth weirs are commonly used to increase the capacity of existing spillways and provide more efficient spillways for new dams due to their high specific discharge capacity compared to the linear weir. In the present study, experimental and numerical investigation was conducted to improve the rectangular labyrinth weir performance. In this context, four configurations were tested to evaluate the influence of the entrance shape and alveoli width on its discharge capacity. The experimental models, three models of rectangular labyrinth weir with rounded entrance and one with flat entrance, were tested in rectangular channel conditions for inlet width to outlet width ratios (a/b) equal to 0.67, 1 and 1.5. The results indicate that the rounded entrance increases the weir efficiency by up to 5%. A ratio a/b equal to 1.5 leads to an 8 and 18% increase in the discharge capacity compared to a/b ratio equal to 1 and 0.67, respectively. In addition, a numerical simulation was conducted using the opensource CFD OpenFOAM to analyze and provide more information about the flow behavior over the tested models. A comparison between the experimental and numerical discharge coefficient was performed and good agreement was found (Mean Absolute Relative Error of 4–6%).

Influence of auxiliary geometric parameters on discharge capacity of piano key weirs

2020 ◽  
Vol 72 ◽  
pp. 101719
Author(s):  
Shanshan Li ◽  
Guodong Li ◽  
Duo Jiang ◽  
Jian Ning
Keyword(s):  
Discharge Capacity ◽  
Geometric Parameters

scholarly journals Effect of Corner Shape on Hydraulic Performance of One-Cycle Rectangular Labyrinth Weirs

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 117
Author(s):  
Omed S. Q. Yousif ◽  
Moses Karakouzian
Keyword(s):  
Discharge Capacity ◽  
Hydraulic Performance ◽  
Acute Angle ◽  
Effective Length ◽  
Hydraulic Efficiency ◽  
Labyrinth Weir ◽  
Rounded Corner ◽  
Side Walls ◽  
The One ◽  
Labyrinth Weirs

The hydraulic performance of rectangular labyrinth weirs has been investigated by many researchers, however, the effects of the corner shape on the hydraulic performance of rectangular labyrinth weirs have not been addressed in the current literature. Accordingly, this experimental study aims to explore the effect of the corner shape of on discharge efficiency of rectangular labyrinth weirs. Five flat-crested rectangular labyrinth weirs, with five different corner shapes, were made of High-Density Polyethylene Plastic (HDPE) and tested in a rectangular flume. Under different overflow discharges, the discharge coefficients for the rectangular labyrinth weirs were determined. The results showed that the shape of corners for rectangular labyrinth weirs was an effective factor. For example, rounding or beveling the corners can significantly increase the discharge capacity of the rectangular labyrinth weirs. However, the rounded corner shape was slightly better than the beveled corner shape. Among all labyrinth weir models tested in this study, the rectangular labyrinth weir with a semi-circular apex showed the highest hydraulic efficiency, while the one with an acute-angle corner shape showed the lowest hydraulic efficiency. For the rectangular labyrinth weir having a semi-circular shape, although the original effective length reduced by about 14%, the discharge coefficient, CL, increased by 16.7% on average. For the rectangular labyrinth weir that has an acute-angle corner shape, although the effective length (LC) of the weir increased by 23%, its discharge capacity decreased by 35.2% on average. Accordingly, improper folding of the side-walls of the rectangular labyrinth weir led to a significant reduction in the weir’s hydraulic performance.

Characteristics of Mesophase Pitch-Based Carbon Fibers as Anode Materials for Lithium Secondary Cells

1995 ◽  
Vol 393 ◽  
Author(s):  
Toshio Tamaki
Keyword(s):  
Carbon Fiber ◽  
Electrochemical Properties ◽  
Carbon Fibers ◽  
Discharge Capacity ◽  
Anode Materials ◽  
Mesophase Pitch ◽  
Good Efficiency ◽  
Heat Treated ◽  
Initial Charge ◽  
Discharge Efficiency

ABSTRACTMesophase pitch-based Carbon Fibers(MPCF) have been investigated as anode materials for lithium secondary cells by examining their physical and electrochemical properties. Discharge capacity and initial charge-discharge efficiency of the materials were studied in relation to the heat treatment temperatures of MPCF. Carbon fiber which was heat treated at about 3,000’C gave the highest discharge capacity(over 300mAh/g), good efficiency (92%) and superior current capability (600mA/g). Carbon fiber heat treated at less than 1,000·C, also has superior discharge capacity(over 500mAh/g) at the first cycle, however efficiency was relatively low. Some of the relationships between structure of MPCF and electrochemical properties are discussed below.

scholarly journals Hydrodynamics and Free-Flow Characteristics of Piano Key Weirs with Different Plan Shapes

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2108
Author(s):  
Yousef Sangsefidi ◽  
Hassan Tavakol-Davani ◽  
Masoud Ghodsian ◽  
Mojtaba Mehraein ◽  
Reza Zarei
Keyword(s):  
Discharge Capacity ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Width Ratio ◽  
Body Volume ◽  
Reverse Trend ◽  
Wide Range ◽  
Magnification Ratio ◽  
High Head ◽  
Discharge Efficiency

This paper focuses on Piano Key Weirs (PKWs) as an effective solution for improving the discharge capacity of spillway systems. The flow behavior in inlet and outlet keys is experimentally studied to analyze the discharge capacity of PKWs with different plan shapes (i.e., rectangular, trapezoidal, and triangular). The results show that in outlet keys, the flow aeration regimes extend to higher values of headwater ratios (Ho/P) by increasing the length magnification ratio (B/w) and apex width ratio (A/w). In addition, the local submergence length is a decreasing function of A/w, especially in high flow heads. While the total interference length enlarges by reducing A/w in lower Ho/P values (Ho/P < 0.5), a reverse trend is observed in higher headwater ratios. PKW performance may also be impacted by the flow contraction and recirculation zone in inlet keys, which intensify in higher values of Ho/P, B/w, and A/w. According to the obtained results, while the discharge coefficient is a decreasing function of A/w in Ho/P > 0.4, it may have a reverse trend in lower head conditions. In addition, a trapezoidal PKW has the highest discharge efficiency in a wide range of the studied domain (Ho/P > 0.25 and B/w ≥ 2). It can improve the discharge efficiency by around 5%, while its body volume is almost 7% smaller than the traditional rectangular PKW. However, for low-length and high-head conditions (B/w = 1 and Ho/P > 0.5), the efficiency a rectangular PKW exceeds that of the other shapes.

scholarly journals Discharge capacity evaluation and hydraulic design of a piano key weir

2018 ◽  
Vol 19 (3) ◽  
pp. 871-878 ◽  
Author(s):  
Xinlei Guo ◽  
Zhiping Liu ◽  
Tao Wang ◽  
Hui Fu ◽  
Jiazhen Li ◽  
...  
Keyword(s):  
Discharge Capacity ◽  
Complex Geometry ◽  
Unit Discharge ◽  
Labyrinth Weir ◽  
Capacity Evaluation ◽  
Hydraulic Design ◽  
New Type ◽  
Multiparameter Optimization ◽  
Piano Key Weir ◽  
New Formula

Abstract A piano key weir (PKW) is a new type of labyrinth weir that increases the unit discharge at the unregulated spillway inlet of the weir. It is considered to be an important structure in water supply and drainage systems. However, its complex geometry makes it difficult to achieve an optimal hydraulic design, and only a few design equations and criteria are available. This study investigates the discharge capacity of a PKW and evaluates the characteristics of its discharge using various sources of experimental data from a database. First, previously proposed discharge capacity formulas are summarized and analyzed. Then, a new formula that integrates the existing test data with the results of dimensional analysis and multiparameter optimization is proposed. The weir characteristics are evaluated using the proposed formula and a mathematical model. The results show that both the proposed formula and numerical model are promising approaches to evaluate the discharge capacity of an A-type PKW and can guide its design.

scholarly journals The effects of dentate crest and a row of consecutive orifices along and below the crest edge on labyrinth weir efficiency

2019 ◽  
Vol 46 (6) ◽  
pp. 552-555
Author(s):  
Zobeideh Ahmadi ◽  
Seyed Asadollah Mohseni Movahed ◽  
Javad Mozaffari
Keyword(s):  
Discharge Coefficient ◽  
Labyrinth Weir ◽  
Laboratory Flume ◽  
Discharge Efficiency

A labyrinth weir is one of the most effective ways of increasing weir discharge efficiency compared with a linear overflow structure. In this study, two proposed models of labyrinth weir, one with a dentate crest and another with a row of orifices along and below the crest edge were compared with a simple labyrinth weir, measuring their effects on the discharge coefficient. Experiments on nine labyrinth weir models were conducted in the hydraulic laboratory flume. These experiments indicated that creation of both dentate crest edge and row of consecutive orifices led to an increased discharge coefficient of between 11 to 25.3% and 31.6 to 52.9%, respectively, relative to simple labyrinth weir. By increasing the upstream head water, the discharge coefficient for the labyrinth weir model with dentate crest and the model with a row of consecutive orifices are closer together and eventually will converge.

scholarly journals Garden footprint area and water use of gated communities in South Africa

Water SA ◽  
2020 ◽  
Vol 46 (2 April) ◽  
Author(s):  
Jacques L du Plessis ◽  
Ashley J Knox ◽  
Heinz E Jacobs
Keyword(s):  
South Africa ◽  
Water Use ◽  
Spatial Data ◽  
Design Guidelines ◽  
Gated Communities ◽  
Gated Community ◽  
Plot Area ◽  
Outdoor Water Use ◽  
Footprint Area ◽  
The Impact

  Gated community homes in South Africa are popular amongst property buyers in urban environments such as cities and metropoles due to the increased security and lifestyle improvements offered. Garden design and layout requirements are prescribed in architectural guidelines compiled by the homeowners associations of these communities. Garden footprint area in gated community homes is of importance to researchers and planners, because of the influence on water use. This study used a quantitative approach to evaluate the spatial data of garden footprint area as a percentage of total plot area for 1 813 gated community homes in different regions of South Africa. The research reviewed how garden footprint area is prescribed and how it is applied in gated community homes. The impact of garden footprint area on water use was also analysed. The results were compared to relevant information lifted from specific architectural design guidelines developed for each gated community. Data from 11 gated communities were analysed and the average garden footprint area was found to be 36% of the total plot area. Gated community homes with a garden area smaller than 100 m2 were found to have limited influence on monthly water consumption, while the water use of gated community homes with a larger garden footprint area increased proportionally with garden footprint area. The seasonal fluctuation of water use is illustrative of garden irrigation and other outdoor water use. The results provided useful input for incorporation in outdoor water use modelling of gated community homes.

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