Pdf in this research, an experimental investigation was conducted to study the characteristics of flow over weirs with semicircular openings. Apr, 2014 weirs not sharp crested are classified according to the shape of their cross section, such as broadcrested weirs, triangular weirs, and trapezoidal weirs. It is frequently used to measure the flow of water in. Four radii of the weir openings were used and three crest heights with either a sharp or semicircular shape for each radius. Weir contractions cause the water flow lines to converge through the notch. Thin plate weirs lab report engineering bibliographies. This calculator finds the water flow rate for a rectangular contracted weir. Kindsvater abstract, an embankmentshaped weir is an embankment overtopped by flood waters. The term nappe is used for the sheet of water flowing over the weir.
The head over the weir is measured and can be used to calculate the water flow rate over the rectangular weir and through the open channel. Studies of flow of water over weirs and dams discharge characteristics of triangularnotch thinplate weirs by john shen abstract the triangularnotch, thinplate weir is a convenient, inexpensive, and relatively precise flow measuring instrument. Its purpose is to report on laboratory investigation on the flow over different types of oblique weirs, including behavior and hydraulic characteristic of the flow, different phenomena in the neighborhood of the weir, and hydraulic parameters and physical laws that govern the process. This laboratory experiment seeks for the understanding of the operation and usage of undershot and overflow weirs. Two common types of sharp crested rectangular weir are the suppressed rectangular weir and the contracted rectangular weir. Several types of weirs are designed for application in natural channels and laboratory flumes. Experimental study of characteristics of flow over weirs with. Discharge characteristics of embankmentshaped weirs. For each experiment, upstream and downstream water levels were measured for different flow rates and boundary conditions. Weirs are structures consisting of an obstruction such as a dam or bulkhead placed across the open channel with a specially shaped opening or notch. Flow of water over weirs free download as pdf file. Weirs and flumes flow measurement instrumentationtools. Flow over a broadcrested weir in subcritical flow conditions.
The results showed that for the sharpcrested 45 and 60 oblique weirs, the discharge coefficient is simply a function of hp. Hydraulics of flow over rectangular labyrinth weirs. Thinplate weirs, when properly installed and maintained, are one of the most accurate means of measuring open channel flows. Its purpose is to report on laboratory investigation on the flow over different types of oblique weirs, including behavior and hydraulic characteristic of the flow, different phenomena in the neighborhood of the. Flow over weirs by john fuller fluid mechanics lab wednesday.
It doesnt matter how thick the weir is except where water flows over the weir through the v. Flow over rectangular sharpcrested weirs springerlink. Pdf experimental study of characteristics of flow over weirs with. A weir is the name given to concrete or masonry structure built across a river or stream in order to raise the level of water on the upstream side and to allow the excess water to flow over its entire length to the downstream side. Therefore, an accurate equation for the discharge coefficient of the triangular broadcrested weirs in over full condition is introduced and could be used with confidence. Weirs may be used to control the discharge, decrease the water slope in canals and to distribute water between canals for irrigation, etc. A rectangular contracted weir has a rectangular opening where the sides are straight up and down. Feb 12, 2017 discharge over a sharpcrested weir it is a special type of weir, having a sharp crest. As in the case of orifice, the actual discharge through a notch or weir can be found by multiplying the theoretical discharge by a coefficient of discharge to allow for energy losses and the adn of the crosssection of the stream at the bottom and sides. By an application of the bernoulli equation the results for flow over weirs can be obtained. Drawdown, as shown in the figure, occurs upstream of the weir plate due to the acceleration of the water as it approaches the weir. Experimental investigation of flow over a triangular broad.
The lengthtowidth aspect ratio ab was varied from 0. For a weir to work correctly it must be mounted so that the crest is centered in the channel, level from side to side, and vertically plumb. Good agreements between the measured values and the values computed from the predictive equation are obtained. Mullinss irrigation manual, introduced in united states by g. He also showed that for the same discharge, the head over the gabion weir is less than that over the solid weir and the head decreases by increasing gabion material particle size. Free flow is the flow condition over a sharpcrested weir when there is free access of air under the nappe. A contracted weir means that the ditch leading up to the weir is wider than the weir opening itself. Good agreements between the measured values and the values. Pdf experimental study of characteristics of flow over.
A series of experiments were conducted by measuring discharge and head over the weir for different weir heights for full width weir. Flow over a crump weir prepared by redahegn sileshi 1 flow over a crump weir prepared by redahegnredi sileshi february, 2009 1. As it has sharp edges, the flow over the notch is frictionless ff0. Determine the maximum discharge over a broadcrested weir 60 meters long having 0.
These are the sources and citations used to research thin plate weirs lab report. Rs 35,000 get latest price flow over weir or open channel apparatus. Weirs can be used to measure flow rates in open channels and rivers common for water supply and sewage plants. D student, department of civil engineering, shahrood university of technology. Good agreements between the measured values and the values calculated from the predictive equation are obtained. Different notch are used, which is rectangular and triangular. Several types of weirs are designed for application in. Since the geometry of the top of the weir is known and all water flows over the weir, the depth of water behind the weir can be converted to a rate of flow. A weir is a concrete or masonry structure which is constructed across a river to measure water flow. Precise flow measurement with a weir requires that the crest of the weir be.
This is a weir having a very broad sill so that the flow of water over the sill may be compared to the flow of water in a channel. Sharpcrested triangular vnotch weirs are overflow structures whose length of crest on the direction of flow is equal to or less than two millimetres. The flow at a given weir breadth and head may be calculated using eq. The objective of this research was to investigate the influence of using one opening or more in weirs on discharge coefficient c d, the hydraulic jump characteristics and velocity distribution downstream of these structures. Results showed that, with an increase of the ratio of the head over the weir crest to the weir height hp, the discharge coefficient decreased nonlinearly and reached a constant value of 0. This report is the conclusion of a comprehensive set of experiments, which were performed on weirs placed obliquely in an open channel. Usbr 1997 suggests using the vnotch weir equations for the following conditions. These are commonly used to measure the volumetric rate of water flow, prevent flooding and make rivers navigable. Broad crested weir, upstream face slope, flow surface pattern, discharge.
Common sources of error in weir flows openchannelflow. Sharp crested rectangular weirs used for discharge measurement purposes in open channel hydraulics are investigated experimentally. The difference of flow rate of water over both type of weirs can be observed and calculated throughout this experiment. Weirs allow hydrologists and engineers a simple method of measuring the volumetric flow rate in small to mediumsized streamsrivers or in industrial discharge locations. Replogle4 abstract longthroated flumes and broadcrested weirs provide a practical, lowcost, flexible means of measuring openchannel flows in new and existing irrigation systems and have distinct advantages over other flume and weir devices. Therefore, a reliable equation for calculating the discharge coefficient of rectangular broadcrested weirs in subcritical flow conditions is presented. Classification or types of notches and weirs fluid mechanics. The discharge over contracted rectangular notch can be calculated as.
The water flowing over the crest comes in contact with the crest line and then springs up from the crest and falls as a trajectory as shown in figure. Determination of flow rate of wastewater using vnotch weir. In order to study the effects of approach velocity and rectangular pool dimensions, nine weir models with different pool lengths a, widths b, and discharge were tested. The iowa institute of hydraulic research has posted an excerpt of one of their older videos, fluid motion in a gravitation field. Weirs are elevated hydraulic structures used to measure flow andor to control the water elevation at outflows from basins and channels 1. A rectangular weir is one type of sharp crested weir, and is of the options that can be used to meter flow rate in an open channel.
The following facts should be considered when a specific type of weir is selected for a given application. Rectangular weir discharge calculator and equations. The depth of flow above the base of a notch is related to the volume flow rate through it, the notch forms a useful flow measurement device. Hydraulics lab flow over weir or open channel apparatus. The word weir will be used to describe any structure used to determine the volume of flow of water from measurements of its depth on a. Pdf minor graduation project report experiments on. Studies of flow of water over dams and weirs discharge characteristics of embank mentshaped weirs by carl. Flow over notches and weirs ppt video online download. Flow over a weir part 2 flume apparatus background please use previous handout flow over a weir for this information. The video, developed with the support of the national science foundation, covers, among other things, the need for aeration of a weir and demonstrates the effect of froude number as it relates to. Flow of water over weirs discharge hydrology volume scribd.
The equation of discharge over a sharpcrested weir q. In this experiment, the rectangular weirs and triangular weirs have been used. The channel at the upstream side of the weir has a crosssectional area of 45 sq meters. Weirs are constructed as an obstruction to flow of water. The ability of the numerical method to simulate the flow over the weir was also investigated using fluent software. Flow characteristics of sharp crested rectangular weir. Aug 28, 2014 in this research, an experimental investigation was conducted to study the characteristics of flow over weirs with semicircular openings. A weir is a barrier across the width of a river or stream that alters the characteristics of the flow and usually results in a change in the height of the water level. To demonstrate the characteristics of flow over weirs. Open the bench control valve and adjust the valve to produce a flow over the weir. The discharge over a notch apparatus shows clearly the use of weirs as simple flow regulators. In open channel hydraulics, weirs are commonly used to either regulate or to measure the volumetric flow rate. They are of particular use in large scale situations. Use a rectangular weir to measure water flow rate in an.
Pdf the flow over broadcrested weirs was simulated by computational fluid dynamic model. In order to conduct the hydro generator test, the open channel design was designed. Organize and deliver effective written, verbal, graphical and virtual communications. Abstract the flow over weirs experiment was conducted to investigate the. Typical cd values for vnotch are in the range of 0.
Flow over ogee weir is also similar to flow over rectangular weir. Vnotch weir is typically used to measure low flows within a narrow operating range. This experiment was conducted on 25 september 2017 by group 4 eh2203d group members. May 25, 2016 this feature is not available right now. In open channel hydraulics, weirs are elevated structures that are used to control outflow andor measure flow from basins and drainage channels. Turn the flume on and open the large orifice valve to let the water into the flume make sure.
Introduction a weir is basically an obstruction in an open channel flow path. The focus in the analysis was to determine accurate flow of the water in the open channel flume. Compute the discharge, if the coefficient of discharge for the weir is 0. Dec 07, 2016 the discharge over narrow crested weir is similar to discharge over rectangular weir. The results show that for the same crest height and the same depth of water over the crest, the discharge passing over the weir. Laboratory experiments were carried out to study the hydraulics of flow over rectangular labyrinth weirs in both free and submerged flow conditions. Aug, 2009 in this study, the experimental upper and lower nappe profiles in rectangular sharpcrested weirs are fitted by quadratic and cubic equations, respectively. Head h should be measured at a distance of at least 4h upstream of the weir. Discharge characteristics of triangularnotch thinplate weirs by john shen studies of flow of water over weirs and dams geological survey watersupply paper 1617b a comprehensive study of the discharge characteristics of triangularnotch thinplate weirs united states government printing office, washington. The crump weir has a triangular profile as is shown in the figure 1. The undershot weir is adjustable allowing a constant head of the upstream reservoir under uniform flow conditions, and prevents sediment buildup. In this research, an experimental investigation was conducted to study the characteristics of flow over weirs with semicircular openings. A significant advantage that weirs and flumes have over other forms of flow measurement is exceptionally high rangeability.
Level the weir apparatus on the hydraulic bench and install the rectangular notch weir. Weirs of different geometric designs are used and the theoretical flow over the weirs is. A clinging nappe gives a higher discharge flow for a given head than a free nappe. Another way to state this is to say that the accuracy of a weir or flume is quite high even at low flow. Under field conditions, though, without proper sizing or regular maintenance a thinplate weir will become increasingly less accurate over time.
Oct 06, 2017 this experiment was conducted on 25 september 2017 by group 4 eh2203d group members. B is the width of the channel in m, and hmax is the maximum expected head over the weir. A weir is an obstruction in a channel that causes water to back up behind it and to flow over it. Gate masters academy g a t e m a s t e r s fluid mechanics 2 flow over notches and weirs dq dl q l 300 dl 900 l dl 33. Four radii of the weir openings were used and three crest. Ensure that the flow is large enough to prevent the outflow from the notch clinging to the notch plate 4. A weir is a concrete or masonry structure which is constructed across the open channel such as a river to change its water flow characteristics.
They note the value of discharge and head, and reduce the flow. In this section, well be discussing flow over weirs. Outcomes conduct various civil engineering experiments related to the course, analyze and evaluate the results with regard to real application. Deviation in any respect will impact the flow accuracy of the installation. In addition, freevortex theory is used to simulate flow over this kind of weirs and determine discharge coefficient. Flow over weirs by john fuller fluid mechanics lab. Che241 lab report flowmeter measurement apparatus fm101 2015. Its purpose is to report on laboratory investigation on the flow over different types of oblique weirs, including behavior and hydraulic. The hydraulic characteristics of flow over rectangular broadcrested weirs with varying upstream slopes. The crest of the ogee weir is slightly rises and falls into parabolic form. Calculate the discharge coefficient for sharpcrested weir experimentally on a hydraulic bench background in open channel hydraulics, weirs are elevated structures that are used to control outflow. At the end of the flume was a sharp crested weir set 150mm above the bottom figure 1. Discharge characteristics of triangularnotch thinplate weirs.
As the water flows over the weir, it reaches a uniform depth of flow h, over the crest. Experimental study of flow behaviour over sharp crested rectangular triangular weir models was carried out in order to determine the flow parameters of the weir models such as head of water, h2, actual discharge,qact, theoretical discharge, qtheo, and discharge coefficient cd. Also, applicable graphs are for 8 curb heights which may not meet rio rancho standards. Water is flowing over a trapezoida weir of 4 meters long under a head of 1 meter. Five laboratory models were used in the experiments with crest heights of 30 cm, 35 cm, 40 cm, 45 cm. Experimental and numerical analysis of flow over a. Sharp crested weirs for open channel flow measurement. Also determine the new discharge over the weir, considering the velocity of approach. Determine the volumetric flowrate using the bench valve by dropping the ball to fill the tank 5. Select and conduct civil engineering experiments to meet a need, and analyze and evaluate the resulting data. The project title was analyzed the water flow in the rectangular open channel flume with rectangular sharp crested weir. In open channel hydraulics, weirs are commonly used to either regulate or to measure the volumetric flow rate, they are of particular use in large scale situations such as irrigation schemes, canals and rivers. Among the engineering problems frequently resulting from this occurrence is. Flow over notches and weirs a notch is an opening in the side of a tank or reservoir which extends above the surface of the liquid.
Discharge over a notch fluid mechanics tecquipment. Broad crested weir broad crested weirs are robust structures that are generally constructed from reinforced concrete and which usually span the full width of the channel. Usbr 1997 provides equations for a standard fully contracted rectangular weir and a standard suppressed weir. Fit the rectangular weir in the flume using the screws 2. This experiment was about discharge of flow of water over weirs which was.
These are commonly used to measure the volumetric rate of. Flow over notches and weirs pdf flow over notches and weirs a notch is an opening in the side of a tank or reservoir which extends above the surface of the liquid. A weir functions by causing water to rise above the obstruction in order to flow over it. Experimental study of flow behaviour over sharp crested rectangular triangular weir models was carried out in order to determine the flow parameters of the weir models such as head of water. It works with and fits on the top of tecquipments digital hydraulic bench h1f, available separately it allows students to do tests on relationships between upstream water level and weir discharge for various different shaped notches. The weir plate should be smooth and plane, especially in the upstream face, while the crest surface and the sides of the notch should have plane surface which make sharp 90degree.