FACULTY OF ENGINEERING & TRADES
SCHOOL OF PROFESSIONAL ENGINEERING
NEW ZEALAND DIPLOMA IN CIVIL ENGINEERING
HYDRAULICS
DE5203
SEMESTER 2 2019
LAB REPORT 1
IMPACT OF JET EXPERIMENT
MUKUND LALJI VALANI
180010428
Introduction
Impact of jets apparatus enables experiments to be carried out on the reaction force
produced on vanes when a jet of water impacts on to the vane. The study of these
reaction forces is an essential step in the subject of mechanics of fluids
Purpose
To investigate the reaction force produced by the impact of a jet of water on to various
vanes.
Apparatus
1. Hydraulic bench
2. Jet apparatus (Shown in the diagram below)
•
•
Weight jockey
Different types of vanes
Figure 1 Apparatus for Experiment
Set up
Figure 2 Set for Experiment
Figure 3 nozzle equipment
Theory
When a jet of water flowing with a steady velocity strikes a solid surface the water is
deflected to flow along the surface. If friction is neglected by assuming an in viscid fluid
and it is also assumed that there are no losses due to shocks then the magnitude of the
water velocity is unchanged. The pressure exerted by the water on the solid surface will
everywhere be at right angles to the surface.
Procedure
The apparatus is first leveled and the lever brought to the balanced position (as
indicated by the tally), with the jockey weight at its zero setting. Note the weight of the
jockey, and the following dimensions: diameter of the nozzle, height of the vane above
the tip of the nozzle when the lever is balanced, and distance from the pivot of the lever
to the center of the vane.
Water is then admitted through the bench supply valve, and the flow rate increased to
the maximum. The force on the vane displaces the lever, which is then restored to its
balanced position by sliding the jockey weight along the lever. The mass flow rate is
established by collection of water over a timed interval. Further observations are then
made at a number reducing flow rates. About nine – ten readings should suffice.
The best way to set the conditions for reduced flow rate is to place the jockey weight
exactly at the desired position, and then to adjust the flow control valve to bring the
lever to the balanced position. The condition of balance is thereby found without
touching the lever, which is much easier than finding the point of balance by sliding the
jockey weight. Moreover, the range of settings of the jockey position may be divided
neatly into equal steps.
The experiment should be run, first with the flat plate, Flat plate at 30 degrees, conical
cup and then with the hemispherical cup.
Quantities
•
Diameter of the nozzle
= 10mm
•
Mass of jockey
= 0.6kg
•
Cross sectional area of plate, A
= 78.5mm2
•
Height of vane above nozzle-exit
= 35mm
•
Weight of water
= 10 Liters/kg
Key Dimension
Calculations
1. Calculating the force
𝐹 × 0.15 = 𝑀𝑔𝑦
𝐹=
𝑀𝑔𝑦
0.15
Mass of the jokey is 0.6
𝐹 = 4𝑔𝑦
And gravity is 9.81, therefore
𝐹 = 39.24𝑦
2. Finding Velocity, 𝒖
𝑢=
𝑀𝑎𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒
(𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 × 𝐶𝑟𝑜𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑝𝑙𝑎𝑡𝑒)
𝑢=
𝑚̇
(1000 × 0.00007854)
𝑢=
𝑚̇
0.07854
𝑢 = 𝑚̇ × 12.76
3. Finding Velocity, 𝒖o
𝑢𝑜 = √𝑢2 − 2 × 𝑔 × ℎ𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑣𝑎𝑛𝑒
𝑢𝑜 = √𝑢2 − 0.6867
4. Flow Rate
=
𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑢𝑠𝑒𝑑
𝑇𝑖𝑚𝑒 𝑖𝑛 𝑚𝑖𝑛𝑠
𝑚̇ =
𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑢𝑠𝑒𝑑
𝑇𝑖𝑚𝑒 𝑖𝑛 𝑠𝑒𝑐𝑠
5. Mass Flow rate
OR
𝑚̇ =
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒
60
Experiment
Aim
•
To demonstrate that the force on a vane is proportional to the rate of delivery of
momentum.
•
To show that you can predict the force on a vane from a combination of its
surface shape and the properties of the jet directed at it.
Procedure
Vane
FLAT PLATE
Flow
rate
(kg/min)
Mass
Distance
Flowrate
y (m)
(kg. s-1)
Velocity
u (m.s-1)
Velocity
u0 (m.s-1)
34246.58
34364.26
30090.27
26785.71
23364.49
20590.25
19815.06
16722.41
570.7763
572.7377
501.5045
446.4286
389.4081
343.1709
330.251
278.7068
7283.105
7308.133
6399.198
5696.429
4968.847
4378.861
4214.003
3556.299
7283.105
7308.133
6399.198
5696.429
4968.847
4378.861
4214.003
3556.299
Vane
ANGLED PLATE
Flow
rate
(kg/min)
Mass
Distance
Flowrate
y (m)
(kg. s-1)
Velocity
u (m.s-1)
Velocity
u0 (m.s-1)
32188.84
32608.7
32502.71
30612.24
26857.65
18326.21
15384.62
536.4807
543.4783
541.7118
510.2041
447.6276
305.4368
256.4103
6845.494
6934.783
6912.243
6510.204
5711.728
3897.373
3271.795
6845.494
6934.783
6912.243
6510.204
5711.728
3897.373
3271.795
72
68
60
47
35
26
20
11
33
30
25
22
16
3
0
Rate of
delivery of
momentum
(kg m.s-2)
4157023.39
4185643.09
3209226.45
2543048.44
1934909.38
1502697.53
1391678.52
991164.626
Rate of
delivery of
momentum
(kg m.s-2)
3672475.06
3768903.56
3744443.47
3321532.67
2556726.85
1190401.09
838921.735
Force F
(N)
2825.28
2668.32
2354.4
1844.28
1373.4
1020.24
784.8
431.64
Force F
(N)
1294.92
1177.2
981
863.28
627.84
117.72
0
Vane
CONICAL CUP
Flow
rate
(kg/min)
Mass
Distance
Flowrate
y (m)
(kg. s-1)
Velocity
u (m.s-1)
Velocity
u0 (m.s-1)
32362.46
30395.14
30303.03
29325.51
26338.89
23492.56
20188.43
18438.84
539.3743
506.5856
505.0505
488.7586
438.9816
391.5427
336.4738
307.3141
6882.416
6464.032
6444.444
6236.559
5601.405
4996.085
4293.405
3921.328
6882.416
6464.032
6444.444
6236.559
5601.405
4996.085
4293.405
3921.328
Vane
HEMISPHERICAL CUP
Flow
rate
(kg/min)
Mass
Distance
Flowrate
y (m)
(kg. s-1)
Velocity
u (m.s-1)
Velocity
u0 (m.s-1)
32017.08
32608.7
29440.63
31055.9
29154.52
25167.79
23696.68
20876.83
533.6179
543.4783
490.6771
517.5983
485.9086
419.4631
394.9447
347.9471
6808.965
6934.783
6261.04
6604.555
6200.194
5352.349
5039.494
4439.805
6808.965
6934.783
6261.04
6604.555
6200.194
5352.349
5039.494
4439.805
116
110
98
89
72
51
42
28
145
139
133
126
114
94
72
55
Rate of
delivery of
momentum
(kg m.s-2)
3712198.68
3274585.8
3254769.89
3048171.6
2458913.38
1956180.31
1444618.11
1205079.14
Rate of
delivery of
momentum
(kg m.s-2)
3633385.66
3768903.56
3072149.25
3418506.63
3012728.04
2245112.81
1990321.64
1544817.35
Force F
(N)
4551.84
4316.4
3845.52
3492.36
2825.28
2001.24
1648.08
1098.72
Force F
(N)
5689.8
5454.36
5218.92
4944.24
4473.36
3688.56
2825.28
2158.2
1. Create a blank result table similar to Tables as above.
2. Make sure the weigh beam is at balance with the jockey weight at the zero
position.
3. Start the hydraulic bench and set to maximum flow.
4. Move the jockey weight until the beam balances again. Note the distance y from
the zero position.
5. Record the flow rate using your hydraulic bench.
6. Reduce the hydraulic bench flow in steps to give at least eight more reading of
distance y and flow in relatively equal increments.
7. Repeat for the other vanes (plates) that you need to test.
GRAPH PLOTS
4500000
4000000
3500000
Axis Title
3000000
2500000
2000000
1500000
1000000
500000
0
0
1000
2000
3000
4000
5000
Axis Title
FLAT PLATE
ANGLED PLATE
CONICAL CUP
HEMISPHERE
6000
RESULTS AND CONCLUSION
From the results obtained and the plots graphed, the following points were concluded:
The predicted value of the Jet force showed larger values than the measured one. This
might be occurred for the following reasons:
•
Errors in taking the reading.
•
Losses in the experiment apparatus.