Download e5-impact of water jet

ENT 257 Fluid Mechanics
Laboratory Module
EXPERIMENT 5
IMPACT OF WATER JET
1.0
OBJECTIVE
To calculate the force produced by a jet of water as it impacts a surface and to compare this
to the theoretical values.
2.0
EQUIPMENT / APPARATUS
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ENT 257 Fluid Mechanics
3.0
Laboratory Module
INTRODUCTION AND THEORY
The apparatus consists of a chamber provided with perspex walls on two opposite
faces. A floating vane fixing rod is provided over the chamber to which the vane is fixed. An
initial balance weight is provided for balancing the mass of the vane. Another sliding weight is
provided to balance the vane fixing rod when the jet strikes the vane.
A nozzle is fixed below the vane through which a vertical jet issues. Water in sump
tank is supplied to nozzle by a circulating pump. A control valve provided controls the
pressure at the jet and hence the flow rate and velocity of the jet.
Two different types of vanes, flat and hemispherical, are provided, giving the jet
deflection of 90° and 180° respectively. The vanes can be interchangeably fixed to the rod.
By adjusting the sliding weight, rod is balanced when the jet is striking the vane. By taking the
moment about the fulcrum, impact force on the vane can be calculated. Nozzles of diameter 6
mm and 8 mm are provided.
Related formula :
No.
1.
Parameter / formula
Cross sectional area of jet, A
A
2.
=
π j2
Discharge Flow rate, Q
Q
=
water volume
time
meter
m3/sec
(1000 liter water
3.
1 m3 water )
Velocity of Jet, V
V
4.
=
=
Q
A
m/sec
Theoretical Force exerted by Flat Vane, FFV
FFV =
wAV2
kg
g
w = specific weight of water = 1000 kg/ m3
g = gravitational acceleration = 9.81 m/s2
5.
Theoretical Force exerted by Hemispherical Vane, FHV
FHV =
2wAV2
kg
g
w = specific weight of water = 1000 kg/ m3
g = gravitational acceleration = 9.81 m/s2
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ENT 257 Fluid Mechanics
Laboratory Module
6.
Experimental Force exerted by Flat Vane & Hemispherical Vane, Fexp
Note : Distance of vane from the fulcrum is 0.135 meter.
Taking moments about the fulcrum,
Fexp x 0.135 = m x L
Fexp =
m x L
0.135
kg
m = mass of sliding weight ,kg
L = Distance of sliding weight from fulcrum, m
7.
4.0
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Percentage error, % error
PROCEDURE
Procedure
Fix the Flat Vane to the fixing rod. Fix the nozzle (diameter, 6mm) in perspex
box at centre by opening the window provided on the right side of the box. Close
the top and side windows.
Adjust the balance weight marked 'B' (left hand side) by using thumbwheel
knob provided, so that vane fixing rod is in horizontal position and the pointers
are matching. Lock the balance weight.
Add sliding weight (0.135 kg ) at L = 300 cm of fixing rod .
Tighten the sliding weight.
Fully open the bypass valve.
Start the pump. Wait under water is pumped into the sump tank.
Slowly close bypass valve. The water -jet will strikes the vane.
Vane fixing rod disturbed.
Try to balance the fixing rod horizontally to red line by adjusting water – jet
impact thru open-close the bypass valve.
Wait until the condition is stabile,
Close the discharge valve of measuring tank.
Turn the swivelling joint pipe towards the measuring tank.
So that water collects in the measuring tank, start stop-watch at 0 litre level and
measure time required for 10 Lit.
Record all your data in Table 1
Repeat the procedure 1 to 9 using Hemispherical Vane with 6 mm nozzle.
Record your data in table 1.
Repeat the procedure 1 to 9 using Hemispherical Vane with 8 mm nozzle.
Record your data in table 1.
Repeat the procedure 1 to 9 using Flat Vane with 8 mm nozzle. Record your
data in table 1.
End of experiment
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ENT 257 Fluid Mechanics
5.0
Laboratory Module
DATA & RESULTS
Observation Table
Table 1
No.
Nozzle
diameter
(mm)
Type of Vane
Time for 10 liter
water
(sec.)
Sliding weight
added
(kg)
Distance of sliding
weight, L
(m)
1.
2.
3.
4.
Analysis
No.
Nozzle
diameter
(mm)
Cross
sectional
Area
2
(m )
Discharge
Flow
rate,
Q
(m3/sec)
Velocity
of Jet,
V
Experimental
Force,
Theoretical
Force,
Fexp
FTheory
(m/sec)
(kg)
(kg)
% error
1.
2.
3.
4.
Show all your calculations in separate sheet.
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ENT 257 Fluid Mechanics
Laboratory Module
6.0.
DISCUSSION / EVALUATION & QUESTION
6.1
Briefly summarize the key results of each experiment
6.2
Explain the significance of your findings
6.3
Explain any unusual difficulties or problems which may have led to poor results
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ENT 257 Fluid Mechanics
Laboratory Module
6.4
Offer suggestions for how the experimental procedure or design could be improved.
6.5
Compare your experimental values with theoretical values given
6.6
Which vane provide the highest exerted force for 6 mm and 8 mm nozzle?.
Explain why?.
6.7
If time for 10 liters water become shorter, what the effect to the exerted
Explain this situation.
force?.
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ENT 257 Fluid Mechanics
7.0
Laboratory Module
DISCUSSION
(Include a discussion on the result noting trends in measured data, and comparing measurements with theoretical predictions when possible.
Include the physical interpretation of the result, the reasons on deviations of your findings from expected results, your recommendations on
further experimentation for verifying your results and your findings.)
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ENT 257 Fluid Mechanics
8.0
Laboratory Module
CONCLUSION
(Based on data and discussion, make your overall conclusion by referring to experiment objective.)
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