Notch and weir apparatus are open-channel flow-measurement rigs used in undergraduate and diploma fluid mechanics laboratories to determine the discharge coefficient of thin-plate weirs by relating the head of water above the crest to the volumetric flow rate. This subcategory covers rectangular, triangular (V-notch) and trapezoidal (Cipoletti) notch plates together with the approach channel, stilling arrangement, hook-and-point gauge and measuring tank that make the classical head-versus-discharge experiment repeatable in a teaching environment.
In a typical Fluid Mechanics lab, this equipment sits alongside orifice, mouthpiece and venturi rigs to give students hands-on exposure to the three families of primary flow measurement: pressure differential, area meters and gravity/head devices. Scientico has manufactured this class of teaching equipment from Ambala since 1993 and supplies engineering colleges and technical institutes in over 60 countries.
Equipment in this range
- Rectangular notch apparatus, thin-plate rectangular notch mounted at the downstream end of a rectangular approach channel; used to derive the coefficient of discharge Cd from head measurements.
- V-notch (triangular) apparatus, 45°, 60° or 90° included-angle triangular notch; preferred for low discharges because head varies as Q2/5, giving good sensitivity at small flows.
- Trapezoidal (Cipoletti) notch apparatus, trapezoidal opening with 1:4 (horizontal:vertical) side slopes so that end-contraction correction is inherently compensated.
- Interchangeable notch plate set, a single approach channel supplied with rectangular, V-notch and trapezoidal plates that clamp against a machined gasket seat, allowing all three experiments on one rig.
- Hook-and-point gauge, vernier-reading gauge on a fixed stand for measuring water surface elevation upstream of the notch to a resolution of 0.1 mm.
- Stilling baffle and approach channel, perforated baffle plate and honeycomb section that condition the flow so the velocity distribution ahead of the notch is close to uniform.
- Collecting tank with sight glass, calibrated measuring tank fitted with a piezometric sight tube and drain valve for volumetric time-rise flow determination.
Where a laboratory does not already own a suitable supply, the notch channel is normally mounted on, or fed by, a hydraulic bench so that a self-contained closed-loop water circuit is available.
Typical experiments demonstrated
- Coefficient of discharge of a rectangular notch. Adjust the inlet valve, allow the head H above the crest to stabilise, and measure the volume collected in the measuring tank over a timed interval to obtain the actual discharge Qact. Theoretical discharge is Qth = (2/3) · L · √(2g) · H3/2, where L is the crest length. Then Cd = Qact / Qth.
- Coefficient of discharge of a V-notch. For a triangular notch with total included angle 2θ, Qth = (8/15) · tan(θ) · √(2g) · H5/2. Students plot log Q against log H and verify the 5/2 slope.
- Coefficient of discharge of a trapezoidal (Cipoletti) notch. Q = Cd · (2/3) · L · √(2g) · H3/2, treated as a rectangular notch because the 1:4 side slopes compensate for end contractions. Values of Cd obtained are compared with the rectangular result at the same head.
- Comparison of sensitivity at low discharges. The same flow is passed sequentially through a rectangular and a 90° V-notch and the readable head resolution compared, illustrating why V-notches are preferred for small flows.
- Effect of end contractions. Rectangular notches with and without end contractions are tested at the same head and the Francis correction (Leff = L − 0.1nH, with n = number of end contractions) is verified.
- Calibration curve and error analysis. A log-log plot of Q against H is fitted for each notch, the exponent extracted and compared with the theoretical exponent (3/2 for rectangular and trapezoidal, 5/2 for triangular), and the scatter interpreted as combined instrument and reading uncertainty.
Key specifications you should ask for
Because open-channel weir readings are sensitive to approach conditions and gauge resolution, the following parameters are worth confirming in writing before purchase:
| Parameter | Typical range |
|---|---|
| Approach channel (L × W × D) | approx. 1000–1500 mm × 200–300 mm × 250–350 mm |
| Notch plate material | stainless steel, 2–3 mm thickness, bevelled crest |
| Channel / tank material | acrylic or transparent PMMA on a steel frame |
| Measuring tank capacity | 40–100 litres with piezometric sight tube |
| Hook-and-point gauge resolution | 0.1 mm vernier |
| Flow range (bench-fed) | approx. 0.1–1.5 L/s |
| V-notch included angles supplied | 45°, 60°, 90° |
| Trapezoidal side slope | 1 horizontal : 4 vertical (Cipoletti) |
| Power supply for pump (if bench-mounted) | 230 V / 50 Hz single phase, or 400 V / 50 Hz three phase |
Applications and syllabus fit
The apparatus maps directly to the Fluid Mechanics and Hydraulics courses common to BTech Mechanical, BTech Civil, BTech Chemical and diploma programmes in India and abroad, and to the corresponding laboratory curricula prescribed by AICTE-aligned university syllabi. Typical target experiments include determination of coefficient of discharge for rectangular, triangular and trapezoidal notches, verification of the discharge equation exponents, and comparative studies of end-contraction corrections. The rigs are also used by polytechnic diploma courses in civil engineering, by irrigation and water-resources electives, and in short-term skill-development programmes on hydraulic measurement.
Standards and compliance
Scientico operates under an ISO 9001:2015 certified quality management system covering the design and manufacture of engineering training equipment. Where a specific unit falls within the scope of an applicable EU product directive, it is manufactured to allow CE marking so it can be placed on the market in the European Economic Area; CE is a conformity marking on the product, not a certification held by the company. Notch and weir apparatus are teaching rigs and are not subject to a dedicated Indian Standard covering their construction; the underlying discharge equations follow the classical thin-plate weir treatment given in standard hydraulics texts and reproduced in reference works such as BIS handbooks on hydraulic measurement. Where an institution requires compliance with a specific national or ASTM standard for a downstream application, that scope should be confirmed at the enquiry stage so the notch geometry and gauge resolution can be specified accordingly.
Ordering and delivery
Units are built to order at the Ambala works and are normally shipped ex-works, FOB Nhava Sheva or CIF the buyer’s nearest gateway port, at the customer’s option. Indicative lead time for a single notch apparatus is in the region of 2–3 weeks from receipt of confirmed order and advance, subject to current workshop load; multi-unit institutional orders are quoted with a firm delivery schedule. Sea freight to most West African, Gulf, South-East Asian and East African destinations is typically 3–6 weeks from despatch, and all quotations, incoterm splits and packing dimensions are treated as estimates until confirmed on the pro-forma invoice.
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Frequently Asked Questions
What is the difference between a rectangular, V-notch and trapezoidal weir?
A rectangular notch has a horizontal crest with vertical sides and gives discharge proportional to H^(3/2). A V-notch is a triangular opening whose discharge varies as H^(5/2), making it far more sensitive at low flows. A trapezoidal (Cipoletti) notch has 1:4 side slopes so that end-contraction losses on a rectangular section are compensated, and it is treated with the rectangular discharge equation.
What is a typical coefficient of discharge for these notches?
For a sharp-crested rectangular notch C_d is usually in the range 0.60 to 0.63, for a 90 degree V-notch approximately 0.58 to 0.62, and for a Cipoletti trapezoidal notch close to 0.62. Exact values depend on head, approach velocity and edge sharpness, and are determined experimentally on this apparatus.
Do you supply the apparatus with a hydraulic bench or as a stand-alone unit?
Both options are available. The notch channel can be supplied as a self-contained rig with its own sump, pump and measuring tank, or as a bench-top channel intended to be fed from an existing hydraulic bench in the laboratory. Please confirm at enquiry which configuration suits your lab layout.
Which notch angles do you offer for the V-notch plate?
Standard included angles are 45, 60 and 90 degrees. Any one angle can be supplied as the default plate, and the interchangeable-plate version ships with all three so the same channel can be used for a full comparative experiment.
Is the apparatus suitable for AICTE and university lab syllabi?
Yes. The rigs cover the standard determination-of-coefficient-of-discharge experiments prescribed in Fluid Mechanics and Hydraulics laboratories for BTech Mechanical, BTech Civil and diploma programmes, and are widely used by engineering colleges and polytechnics in India and abroad.
What are your export terms and lead time?
Units are built to order in Ambala and shipped FOB Nhava Sheva or CIF the buyer’s nearest port at the customer’s option. Indicative lead time for a single apparatus is 2 to 3 weeks from advance, plus sea freight of typically 3 to 6 weeks to most destinations. All figures are estimates confirmed on the pro-forma invoice.
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