Feb 12, 2017 discharge over a sharpcrested weir it is a special type of weir, having a sharp crest. The term nappe is used for the sheet of water flowing over the weir. 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. Che241 lab report flowmeter measurement apparatus fm101 2015. Four radii of the weir openings were used and three crest. Several types of weirs are designed for application in. 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. The equation of discharge over a sharpcrested weir q. Laboratory experiments were carried out to study the hydraulics of flow over rectangular labyrinth weirs in both free and submerged flow conditions.
This calculator finds the water flow rate for a rectangular contracted weir. Discharge characteristics of embankmentshaped weirs. The project title was analyzed the water flow in the rectangular open channel flume with rectangular sharp crested weir. Sharp crested weirs for open channel flow measurement. Drawdown, as shown in the figure, occurs upstream of the weir plate due to the acceleration of the water as it approaches the weir. A weir functions by causing water to rise above the obstruction in order to flow over it.
Good agreements between the measured values and the values. Open the bench control valve and adjust the valve to produce a flow over the weir. Lab report on broad crested weir cheap assignment helphnd. Usbr 1997 provides equations for a standard fully contracted rectangular weir and a standard suppressed 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. Pdf experimental study of characteristics of flow over weirs with.
It is frequently used to measure the flow of water in. To demonstrate the characteristics of flow over weirs. Wan nur fatini norhasmanina kamalina azzyati nur alia nabila. Bureau of reclamation has conducted many weir tests over several decades using weirs with particular dimensions usually bs in 1 ft. In addition, freevortex theory is used to simulate flow over this kind of weirs and determine discharge coefficient. Classification or types of notches and weirs fluid mechanics. 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. Oct 06, 2017 this experiment was conducted on 25 september 2017 by group 4 eh2203d group members. Weirs and flumes flow measurement instrumentationtools. The crump weir has a triangular profile as is shown in the figure 1. Several types of weirs are designed for application in natural channels and laboratory flumes. In open channel hydraulics, weirs are commonly used to either regulate or to measure the volumetric flow rate. As the water flows over the weir, it reaches a uniform depth of flow h, over the crest.
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. The hydraulic characteristics of flow over rectangular broadcrested weirs with varying upstream slopes. 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. Generally ogee shaped weirs are provided for the spillway of a storage dam. In open channel hydraulics, weirs are elevated structures that are used to control outflow andor measure flow from basins and drainage channels. Weirs can be used to measure flow rates in open channels and rivers common for water supply and sewage plants. The discharge over contracted rectangular notch can be calculated as. Level the weir apparatus on the hydraulic bench and install the rectangular notch weir. 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. Hydraulics of flow over rectangular labyrinth weirs. Precise flow measurement with a weir requires that the crest of the weir be. These are the sources and citations used to research thin plate weirs lab report.
Determine the maximum discharge over a broadcrested weir 60 meters long having 0. Experimental study of characteristics of flow over weirs with. So, the discharge over the weir, therefore height of weir should be 2. These are commonly used to measure the volumetric rate of. Typical cd values for vnotch are in the range of 0. 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. The iowa institute of hydraulic research has posted an excerpt of one of their older videos, fluid motion in a gravitation field. At the end of the flume was a sharp crested weir set 150mm above the bottom figure 1. The crest of the ogee weir is slightly rises and falls into parabolic form. A weir is a concrete or masonry structure which is constructed across a river to measure water flow. By an application of the bernoulli equation the results for flow over weirs can be obtained. A series of experiments were conducted by measuring discharge and head over the weir for different weir heights for full width weir. Determination of flow over broadcrested weirs is more difficult than for knifeedge weirs, and there are several complicating factors, such as the degree of detachment of the nappe.
These are commonly used to measure the volumetric rate of water flow, prevent flooding and make rivers navigable. Flow over notches and weirs ppt video online download. Experimental and numerical analysis of flow over a. Discharge characteristics of triangularnotch thinplate weirs. 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. Aug 28, 2014 in this research, an experimental investigation was conducted to study the characteristics of flow over weirs with semicircular openings. Head h should be measured at a distance of at least 4h upstream of the weir. Among the engineering problems frequently resulting from this occurrence is. Thin plate weirs lab report engineering bibliographies. Flow over a weir part 2 flume apparatus background please use previous handout flow over a weir for this information. 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.
The results showed that for the sharpcrested 45 and 60 oblique weirs, the discharge coefficient is simply a function of hp. Pdf in this research, an experimental investigation was conducted to study the characteristics of flow over weirs with semicircular openings. Ensure that the flow is large enough to prevent the outflow from the notch clinging to the notch plate 4. A significant advantage that weirs and flumes have over other forms of flow measurement is exceptionally high rangeability. Weirs are elevated hydraulic structures used to measure flow andor to control the water elevation at outflows from basins and channels 1. 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. Dec 07, 2016 the discharge over narrow crested weir is similar to discharge over rectangular weir. Rebeka sultana objectives the purpose of this experiment is to demonstrate the characteristics of flow over weirs. 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. Broad crested weir, upstream face slope, flow surface pattern, discharge.
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. Thinplate weirs, when properly installed and maintained, are one of the most accurate means of measuring open channel flows. 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. It doesnt matter how thick the weir is except where water flows over the weir through the v.
May 25, 2016 this feature is not available right now. 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. Turn the flume on and open the large orifice valve to let the water into the flume make sure. 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. 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. The channel at the upstream side of the weir has a crosssectional area of 45 sq meters. Its purpose is to report on laboratory investigation on the flow over different types of oblique weirs, including behavior and hydraulic. In this section, well be discussing flow over weirs. 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. For each experiment, upstream and downstream water levels were measured for different flow rates and boundary conditions. Pdf experimental study of characteristics of flow over. Two common types of sharp crested rectangular weir are the suppressed rectangular weir and the contracted rectangular weir.
Another way to state this is to say that the accuracy of a weir or flume is quite high even at low flow. Determine the volumetric flowrate using the bench valve by dropping the ball to fill the tank 5. Flow characteristics of sharp crested rectangular weir. Common sources of error in weir flows openchannelflow. Flow of water over weirs discharge hydrology volume scribd. This experiment was conducted on 25 september 2017 by group 4 eh2203d group members. Fit the rectangular weir in the flume using the screws 2. The focus in the analysis was to determine accurate flow of the water in the open channel flume.
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. Hydraulics lab flow over weir or open channel apparatus. 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 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. Good agreements between the measured values and the values calculated from the predictive equation are obtained. A weir is an obstruction in a channel that causes water to back up behind it and to flow over it. Weirs are commonly used for measurement of open channel flow rate. Vnotch weir is typically used to measure low flows within a narrow operating range. Flow of water over weirs free download as pdf file. Select and conduct civil engineering experiments to meet a need, and analyze and evaluate the resulting data.
Also determine the new discharge over the weir, considering the velocity of approach. Abstract the flow over weirs experiment was conducted to investigate the. Therefore, a reliable equation for calculating the discharge coefficient of rectangular broadcrested weirs in subcritical flow conditions is presented. Weir contractions cause the water flow lines to converge through the notch. 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. Also, applicable graphs are for 8 curb heights which may not meet rio rancho standards. A contracted weir means that the ditch leading up to the weir is wider than the weir opening itself. Determination of flow rate of wastewater using vnotch weir. Kindsvater abstract, an embankmentshaped weir is an embankment overtopped by flood waters. 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. 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.
A rectangular contracted weir has a rectangular opening where the sides are straight up and down. Water is flowing over a trapezoida weir of 4 meters long under a head of 1 meter. The undershot weir is adjustable allowing a constant head of the upstream reservoir under uniform flow conditions, and prevents sediment buildup. Pdf the flow over broadcrested weirs was simulated by computational fluid dynamic model. 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. Sharpcrested weirs for open channel flow mesurement harlan h. Studies of flow of water over dams and weirs discharge characteristics of embank mentshaped weirs by carl. This laboratory experiment seeks for the understanding of the operation and usage of undershot and overflow weirs. 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.
Good agreements between the measured values and the values computed from the predictive equation are obtained. Weirs for openchannel flow measurement 2 both the type of weir to be used and the dimensions of the weir. This report is the conclusion of a comprehensive set of experiments, which were performed on weirs placed obliquely in an open channel. They note the value of discharge and head, and reduce the flow. The discharge over a notch apparatus shows clearly the use of weirs as simple flow regulators. Flow over a broadcrested weir in subcritical flow conditions. 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. Sharpcrested triangular vnotch weirs are overflow structures whose length of crest on the direction of flow is equal to or less than two millimetres. Mullinss irrigation manual, introduced in united states by g.
The flow at a given weir breadth and head may be calculated using eq. Doc che241 fluid mechanics lab report flow over weirs arif. Different notch are used, which is rectangular and triangular. Discharge over a notch fluid mechanics tecquipment. 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. The lengthtowidth aspect ratio ab was varied from 0. Use a rectangular weir to measure water flow rate in an. 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.
The difference of flow rate of water over both type of weirs can be observed and calculated throughout this experiment. Usbr 1997 suggests using the vnotch weir equations for the following conditions. Pdf minor graduation project report experiments on. Hydraulic characteristics of flow over weirs with circular. Five laboratory models were used in the experiments with crest heights of 30 cm, 35 cm, 40 cm, 45 cm. They are of particular use in large scale situations. Organize and deliver effective written, verbal, graphical and virtual communications. Flow over rectangular sharpcrested weirs springerlink. Weirs allow hydrologists and engineers a simple method of measuring the volumetric flow rate in small to mediumsized streamsrivers or in industrial discharge locations. Deviation in any respect will impact the flow accuracy of the installation. Weirs are constructed as an obstruction to flow of water. Four radii of the weir openings were used and three crest heights with either a sharp or semicircular shape for each radius. Sharp crested rectangular weirs used for discharge measurement purposes in open channel hydraulics are investigated experimentally. This bibliography was generated on cite this for me on wednesday, january 24, 2018 ebook or pdf.
Compute the discharge, if the coefficient of discharge for the weir is 0. Aug, 2009 in this study, the experimental upper and lower nappe profiles in rectangular sharpcrested weirs are fitted by quadratic and cubic equations, respectively. Free flow is the flow condition over a sharpcrested weir when there is free access of air under the nappe. B is the width of the channel in m, and hmax is the maximum expected head over the weir. The ability of the numerical method to simulate the flow over the weir was also investigated using fluent software.
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 clinging nappe gives a higher discharge flow for a given head than a free nappe. Weirs may be used to control the discharge, decrease the water slope in canals and to distribute water between canals for irrigation, etc. 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. Under field conditions, though, without proper sizing or regular maintenance a thinplate weir will become increasingly less accurate over time. Introduction a weir is basically an obstruction in an open channel flow path. In this research, an experimental investigation was conducted to study the characteristics of flow over weirs with semicircular openings.
Experimental investigation of flow over a triangular broad. Outcomes conduct various civil engineering experiments related to the course, analyze and evaluate the results with regard to real application. D student, department of civil engineering, shahrood university of technology. Flow over a crump weir prepared by redahegn sileshi 1 flow over a crump weir prepared by redahegnredi sileshi february, 2009 1. Flow over weirs by john fuller fluid mechanics lab. Rectangular weir discharge calculator and equations. Flow over ogee weir is also similar to flow over rectangular weir. Weirs of different geometric designs are used and the theoretical flow over the weirs is.
Flow over weirs by john fuller fluid mechanics lab wednesday. The following facts should be considered when a specific type of weir is selected for a given application. 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. In order to conduct the hydro generator test, the open channel design was designed. This experiment was about discharge of flow of water over weirs which was. Rs 35,000 get latest price flow over weir or open channel apparatus.