FLOW MEASUREMENTS

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• FLOW MEASUREMENTS
• (Additional Problems)
• Find the diameter of a sharp edged orifice
  sufficient to discharge 3x106 litres of water per
  day. Under a constant head of 12m. Take Cd0.62
• A closed tank partially with water upto a height
  of 2m has an orifice of 2.75cm diameter at its
  bottom. Determine the air pressure over the water
  surface for a discharge of 5 lps, through the
  orifice, Cd0.62

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3. Water is discharged vertically upwards through
a 5cm diameter orifice under a pressure of
180N/cm2. CV for the orifice is 0.92. Determine
the height to which the jet will rise, when i)
there is no air friction ii) when the friction
produces a retardation of 2m/s2.
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4. In performing an experiment to determine the
different coefficients of a sharp edged orifice,
a jet of water issuing horizontally from the
orifice of 2.5cm diameter under a constant head
of 1.5m fell through 0.9m vertically and struck
the ground at 2.3m horizontally from Vena
contracta. The time required to discharge
91litres of water was found to be 53 seconds.
Find the values of Cd, CV and CC for the orifice.
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5. A Jet of water issuing from a vertical orifice
0.025m diameter under a constant head of 1.5m
falls 0.915m vertically, before it strikes the
ground at a distance of 2.288m, measured from
Vena contracta horizontally. The discharge was
found to be 0.102 m3/min. Determine Cd, CV, CC,
Cr for the orifice.
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6. The centre of an orifice is situated 60cm
above the bottom of a vessel containing water to
a depth of 2.4m. Assuming CV0.98. Estimate how
far the water in the jet issuing from the orifice
in the side of the vessel will fall in moving
horizontally a distance of 1m from the Vena
contracta.
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7. A large tank has a circular sharp edged
orifice 2.5cm diameter in a vertical side at a
depth 0.6m below the constant water level. The
jet diameter at Vena contract is found to be 2cm.
The water is found to be 2cm . The water
discharged is collected in a vessel having the
inside dimensions of 1.2m x 0.6m x 0.6m. The time
required to fill the vessel is 7minutes.
Calculate Cd, CV CC.
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8. Oil of S0.85 issues from a 5cm diameter
orifice under a pressure of 12N/cm2. The diameter
of jet at Vena contracta is 4cm and the discharge
is 20 lps. What is the coefficient of
velocity? 9. A rectangular orifice 0.9m wide,
1.2m deep is discharging water from a vessel. The
top edge of the orifice is 0.6m below the water
surface in the vessel. Calculate the discharge
through the orifice if Cd0.6 and the percentage
error if the orifice is treated as a small
orifice.
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10. A closed tank contains kerosene S0.8 to a
depth of 3m. The top portion of the tank contains
air under a pressure of 27.5kpa. If a sharp edged
circular orifice of 3cm diameter Cd0.62 is
provided at the bottom of the tank, estimate the
discharge through the orifice.
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11. A standard mouthpiece 5cm in diameter
discharges water. Determine the maximum head
under which the flow would take place without the
occurrence of separation at Vena contracta. The
coefficient of discharge for the mouth piece is
0.8, separation occurs when the absolute pressure
is 2.44m of water.
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12. Find the discharge through an external
cylindrical mouth piece of 10cm in diameter
flowing under a head of 3.5m. What is the
pressure at Vena contracta? Take CC0.62.
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13. Calculate the value of V - notch angel to
discharge 400lps under a head of 0.6m, assuming
Cd0.60. 14. During a test in a laboratory the
water passing through a venturimeter is made to
flow over a 900V notch. Diameter at inlet is 25cm
an that at the throat is 10cm. The pressure
difference is 0.34m when the head over the
V-notch is steady at 18.2cm. If Cd for the
venturimeter is 0.97, what is the coefficient of
discharge of the V-Notch?
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15. Discharge varies in a rectangular channel
from 0.0057 to 0.142 m3/s. At what height should
a 900 V-notch be placed above the bed of the
channel, if the depth should not exceed 1.2m, in
the channel? What will be its depth for minimum
discharge?
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16. A 900 V-notch is provided in a rectangular
channel 1.5m wide in order to measure the channel
discharge the channel is designed to carry a
maximum discharge of 0.4m3/s. With a depth not
exceeding 1.8m. Find the position of the apex of
the notch from the bed of the channel.
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17. During an experiment in a laboratory 0.9
litres of water is flowing per second over a
V-notch when the head is 5cm and 5 litres/sec,
when the head is 10cm. Determine the values of k
n in the equation QKHn. 18. A triangular weir
has one side sloping at 450 and the other side
Z(H)1V. Calculate the values of Z which gives a
discharge of 0.12m3/s under a head of 0.3m.
Cd0.6
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19. Water flows through a 900 V-notch with a free
surface of water at a height of 10cm from the
crest. The corresponding flow rate is 1000lpm. If
the height above the crest is increased by 50,
what would be the new flow rate? 20. A
rectangular channel 6m wide carries a flow of
1.5m3/s. A rectangular sharp crested weir is to
be installed near the end of the channel to
create a depth of 1m. Upstream of the weir,
calculate the necessary weir height. Assume
Cd0.62.
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21. A suppressed weir having a crest length of
4m, discharges under a head of 40cm. The height
of the weir crest above the channel bed is 1m.
Find the rate of discharge. 22. A rectangular
sharp crested weir is required to discharge 645
m3/s of water under a head of 1.2m. If the
coefficient of discharge is 0.6 and the velocity
of approach near the weir is 1 m/s, find the
length of the weir required.
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23. A discharge of 1800m3/s is to pass over a
rectangular weir which is divided into a number
of spans of 10m each. If the velocity of approach
is 4m/s, find the number of opening required such
that the head over the crest does not exceed
2m. 24. A waste weir has to pass a flood
discharge of 3m3/s. find the length of the broad
crested weir to suit the discharge such that the
depth of water over the weir crest will not be
more than 42cm. Take Cd0.97.
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25. A 3m wide rectangular irrigation canal
carries water with a discharge of 6m3/s. what
height of rectangular weir installed across the
canal will raise the water surface to a level of
2m above the floor? 26. A rectangular weir
0.75m high 1.5m long is to be used for
discharging water from a tank under a head of
0.5m. Estimate the discharge a) when it is used
as suppressed weir. b) when it is used as a
contracted weir. Take Cd0.61.
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27. A trapezoidal sharp crested weir has a base
width of 1.2m side slopes of 1.5H to 1V.
Calculate the discharge over the weir for a head
of 35cm. Take Cd0.62. 28. Calculate the bottom
width and side slopes of a trapezoidal notch to
discharge 4m3/s at a head of 1.5m and 1.2m3/s at
a head of 0.75. Assume Cd0.63.
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29. A Cipolletti weir of crest length 0.6m
discharges water under of 0.36m. Find the
discharge over the weir if the channel is 0.8m
wide 0.5m deep. Take Cd0.6.