|Title of Invention||
STILLING BASIN FOR CIRCULAR OUTLETS
|Abstract||A constricted width flow meter has been proposed for discharge measurement in open channels. It is envisaged to be a very simple device, which is not onh easy to construct. operate and but maintenance free also. The rate of flow can be estimated with accuracy under both free and submerged flow conditions. The device can find application lor measurement of discharge in open field channels of rectangular shape. The upstream and downstream depth of water are represented as hu and hd respectively as shown in Figure la. Points 1, 2. 3, 4 and 5 (Figure lb) are representing flow direction, inlet portion, throat portion outlet portion and downstream portion of the flowmeter respectively.|
|Full Text||Field of Invention This invention relates to the development of a new flowmeter, which can be used for flow measurement in open channels.
Background of the invention
Measurement of water in open channels is quite important for accurate assessment and efficient management of water resources. Weirs, flumes and gates are being used to determine discharge in open channels since long. Most of the earlier critical depth flumes like Parshall flumes (Parshall,R.L., "The Improved Venturi Flume", Transactions, ASCE, 89, 841-880, 1926) , Cut throat flumes (Ackers, P, White, W.R., Perkins J. A. and Harrison, A.J.M., "Weirs and Flumes for Flow Measurement", John Wiley & Sons Ltd., Chichester, U.K., 1978.) etc. are not easy to construct. The Parshall flumes are to be constructed exactly to the recommended dimensions, requiring a greater skill and the workmanship. Each flume is to be leveled accurately in both the longitudinal and the transverse directions and they are not geometrically similar. For each discharge range, different dimensions of the flume are recommended. In submerged flow conditions, a correction to the discharge is to be applied for which graphs are available for different widths of throats and discharges. Furthermore, these are more expensive to build due to large transition lengths.
In the Cutthroat flume, a stage discharge relation needs direct calibration due to absence of throat section, which causes curvilinear flow and a non-hydrostatic pressure distribution. Due to the complex hydraulic behavior, theses should either correspond exactly with a flume that has been calibrated earlier or should be calibrated before being put to use. Keeping in view some of these difficulties, the proposed constricted width flow meter having sudden expansion at downstream end and with a simplified geometry was considered, for studying the flow characteristics under free and submerged flow conditions. The research included laboratory testing of the proposed flow meter.
Object of invention
The object of the invention is to develop a device which should be simple in construction, easy in operation and requires minimum maintenances for the measurement of the discharge in the open channels used for irrigation. It should be applicable to field and irrigation channels to have practical utility.
Summary of invention
A fairly accurate measurement of flow in rectangular field channels is required in many irrigation projects for the efficient use of the irrigation water. Metering makes the farmer conscious of the proper use of water and prevents overuse and wastage of water. The overall efficiency of the water distribution in canals can be realized only if proper accounting is done about the discharge and losses at all stages from the head-works to the point of application in the field. The measurement of discharge measurement has been done by using specially designed simple flow meter which is based on the concept of creating a critical flow at the throat section. At the critical state of flow, there exist a definite relationship between stage (depth of flow) and discharge. The proposed flow meter is found to be geometrically similar, so it can be employed to measure discharge in open channel of rectangular cross section having any size. It can be used under free as well as in submerged flow conditions. The Fig.2 can be used to calculate the coefficient of discharge K of the free and submerged flow and putting in the equation (2), the discharge can be estimated. It is envisaged to be a very simple device. It can be constructed in the field very easily and can be employed for measurement of discharge of the irrigation field channels very easily. Moreover, it is maintenance free, no creates no choking of flow and requires no skill workmanship to construct.
The geometry of the flow meter as per Fig 1 is constructed in the field channel of rectangular cross section of width B.
For free flow, only hu (upstream depth of flow) is to be measured in the constricted width flow meter. The value of K can be calculated from equation (1) for the given value of b, as marked on Fig.2.
Substituting the value of K in the equation (2), the discharge can be calculated for known hu and b under free flow conditions.
In case of submerged flow condition, downstream depth hd an corresponding upstream depth
hu are measured and, the value of K can be obtained from Fig.2. The discharge can be
calculated by using equation 2 substituting appropriate value of constant K.
Brief description of the accompanying drawing
The attached drawing (Fig. 1) illustrates the plan and elevation of the present invention.
Fig. 1 shows the systematic arrangements of the flow meter in terms of width of the throat of
the flow meter (b), which is half of the width of the channel (B).
Fig. 1(a) shows the elevation view of the flow meter.
Fig. 1(b) shows the plan view of the flow meter along with upstream and downstream depth
of flow and a hydraulic jump.
Detailed description of the invention with reference to drawing
The attached drawing (Fig.l) shows in plan and elevation of the recommended design of flow meter to be used for discharge measurement in open channels of rectangular shape. The dimensions are expressed in terms of width of channel B. It consists of a converging inlet section (slope 1V:2H), a throat section of uniform width b (where b = B/2, B = width of the channel) and a diverging portion of width B as shown in Fig.l. Water flows along the direction (1) and passes through converging section (2) and later on goes through throat or constriction section (3). When flow is sub critical, the reduction of width of the channel causes lowering in depth of flow at constricted section (3). By constriction of width of
channel to half, a critical flow condition may be obtained by converting major part of the upstream head in to kinetic energy at the control section (3). There is a definite relation between the upstream depth of flow and the discharge. Such a section with critical flow above the weir crest is required to make upstream head hu independent of downstream conditions. This condition can be visualized by formation of hydraulic jump downstream of the control section (4).
An abrupt diversion (4) is provided in the present devise after the throat portion, while ignoring the head loss in the device. In submerged flow or non-modular flow conditions, both upstream depth at section (1) and downstream depth at section (5) are to be measured for the purpose of discharge measurement.
The suggested device can be used for discharge measurement in irrigation channels having rectangular shape. It is a quite simple devise and can be constructed with a small cost as compared to other existing devices used for flow measurement in irrigation channels.
1. A flow meter which is used for discharge measurement in open channels comprises of (a) a rectangular flow channel of width B (1) in which water enters,
(b) a straight inside converging inlet portion (2) having a slope 1V:2H and length equal to half the width of rectangular channel, wherein V = vertical dimension, H = horizontal dimension
(c) a straight and parallel vertical throat section (3) whose width and length are equal to half the channel width,
(d) a sudden expanding portion downstream (4) whose width is equal to one fourth of throat width on either side,
(e) a downstream channel of width equal to twice the throat width (5) where flows later on (f) having a total length of flow meter equal to width of channel.
2. The flow meter as claimed in claim 1 has converging inlet portion with slope 1 V:2H whose length equal to throat width of flowmeter.
3. The flow meter as claimed in claim 1 has a straight throat portion of width and length equal to throat width of flowmeter.
116-DEL-2006-Description (Complete) (05-02-2008).pdf
|Indian Patent Application Number||116/DEL/2006|
|PG Journal Number||07/2009|
|Date of Filing||17-Jan-2006|
|Name of Patentee||Dr. Arun Goel|
|Applicant Address||ASSISTANT PROFESSOR, CIVIL ENGINEERING DEPARTMENT NATIONAL INSTITUTE OF TECHNOLOGY (DEEMED UNIVERSITY), KURUKSHETRA. 136119, HARYANA.|
|PCT International Classification Number||NA|
|PCT International Application Number||N/A|
|PCT International Filing date|