Exp-5 V-NOTCH

AIM :     To determine the coefficient of discharge of v – notch.

APPARATUS :    V-Notch equipment, Bucket, Inclined manometer, stop-watch.

THEORY:

The V-notch weir is a triangular channel section, used to measure small discharge values. The upper edge of the section is always above the water level, and so the channel is always triangular simplifying calculation of the cross-sectional area. V-notch weirs are preferred for low discharges as the head above the weir crest is more sensitive to changes in flow compared to rectangular weirs.

V-notch

By applying Bernoulli equation (conservation of energy equation) to a simplified flow model of a V-notch, we can develop the following relationship:clip_image003

PROCEDURE :

(1) Fill the overhead tank & maintain constant overflow.

 (2) Start filling the v-notch tank with water up to the v-notch.,&  obtain steady state.

(3) Allow water to flow through v-notch after getting steady state.

 (4) Measure the head of water above v-notch from inclined manometer.

(5) Note down volumetric flow rate through v-notch.

 (6) Similarly take readings for different flow rate & head over the v-notch.

GRAPHS :           Q = CD 8/15 tanΘ/2 √2g H5/2    Q = K H5/3  ; K = CD 8/15 tanΘ/2 √2g

logQ = logK  + 5/2logH      (1) log H vs. log Q. Obtain intercept & slope.

RESULT :             The value of discharge coefficient of v-notch obtained from,

Calculation : CD = _____. Graph : CD = _____.

Conclusion:

Observations:

(1) Angle of v-notch ,Θ =  680

(2) Angle of inclined manometer, ∝ =  310

(3) Temp. of water, t = ______ °C.

OBSERVATION TABLE :

 

Sr. No. Volume of water collected, m3 Time , t sec. Inclined manometer reading.
1.
2.
3.
4.

CALCULATIONS :

(1) Volumetric  flowrate,  Q =  Vol. of water collected/time,t sec.

=  _______  m3 / sec.

(2) Height of water in tank, H = Inclined manometer Reading x sin ∝

= _____ mt.

(3) Discharge coefficient , CD =  (15 /8) Q . 1/tanΘ/2 √2gH5

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