King faisal university
College of engineering
Department of mechanical & civil
engineering
Experiment#5
Fluid mechanics Lab
Orifice and Jet Flow
Tested by [Group (B)]
Arafat . A . Ali
ID# 213189413
Experiment date :- Feb 7th,2016
Submit date :- Mar 21th,2016
Engr312
Engr312 FLUID MECHANICS
Laboratory Experiment #5
Orifice and Jet Flow
Objective:
Studying the flow through small orifice discharging to atmosphere.
Calculating the coefficient of discharge (Cd).
Calculating the coefficient of velocity (Cv).
Calculating the coefficient of contraction (Cc)
Introduction
An Orifice is an opening in the side or base of tank or reservoir
through which fluid is discharge in the form of a jet.
The discharge will depend upon the head of the fluid (H) above the
level of the orifice.
The term small orifice means that the diameter of the orifice is small
compared with the head producing flow.
List of Equipment
1. Basic hydraulic bench
2. Osborne Reynolds Demonstration Apparatus
3. Hydrostatic pressure apparatus
4. Bernoullis Demonstration apparatus
5. Dead weight calibrator
6. Orifice and free jet flow apparatus
7. Orifice discharge apparatus
8. Free and Forced vortices apparatus
9. Compressible flow bench
Theory:
Two reasons for the difference between theoretical and actual discharge.
First: The velocity of jet is less than the velocity calculated because there is losses
of energy between point A and B.
Vactual Cv .Vtheo. Cv 2 gH
,Cv is the coefficient of velocity
Second: The stream line of the orifice contract reducing the area of flow. (Vena
Contraction)
Aactual Cc . A
Where. Cc is the coefficient of contraction.
Qactual Cv .Cc . A 2 gH
Qactual Cd A 2 gH
Cd in the range [0.6-0.65]
Measurement of Jet Trajectory
Procedure:
1. Install the required orifice
2. adjust the overflow pipe to obtain a required level in the tank
3. Open the water supply valve to obtain a steady flow with minimum overflow
4. wait until the level in the tank and jet profile is stable before adjusting the probes tips
to be in-line with the center of the jet and record the probe tip profile as well as the Y =
0 mark
5. Record the flow volume by using the stopwatch and bench-measuring tank.
Data & Results:
Table 1 : Parameters of the apparatus and some reading from the experiment
Water level, H
379 (mm)
Volume, Lt
Time, s
16.44
0.30414 * 10-3 (m3/s)
Flow rate, QA = volume/time
Diameter of orifice, m
0.013
Area (m )
0.000133
Table 2 : Reading from the experiment
YTHEORETICAL
=
X1
40
Y1
X2
4H
1.055
2 YH
Error %
38.93584
5.540897
X2
80
Y2
4.221
87.0632
77.83641
X3
120
Y3
12
9.499
134.8777
250.1319
X4
160
Y4
21.5
16.887
180.5381
461.3456
X5
200
Y5
31
26.385
216.7856
461.4776
X6
240
Y6
45.5
37.995
262.6366
750.5277
X7
280
Y7
62
51.715
306.5811
1028.496
X8
320
Y8
78.5
67.546
344.9725
1095.383
X9
360
Y9
100
85.488
389.3584
1451.187
X10
400
Y10
122
105.541
430.0605
1645.91
Analysis and Calculations
The theoretical velocity
2 gH
Vth=
= 2.72 m /s
The actual velocity
0.360
Vact=Vx =
-
2Y
g
Coefficient of velocity Cv
Cv=
V act
V th
2(0.1)
9.81
= 2.52 m/s
= 0.926
The actual volume flow rate
=
= 0.30414 * 10-3 (m3/s)
The theoretical volume flow rate th
2
2 gH
2
d
(0.013)
th = VA = 4
= 4
Coefficient of discharge
0.05
16.44
2 * 9.81 * 0.379
= 0.3619* 10-3 (m3/s)
Cd =
Q act
Q th
0.3041410
3
0.361910
= 0.84
The coefficient of contraction Cc
Cd
Cv
Cc =
= 0.907
X versus 2
500
400
300
200
100
0
0
50
100 150 200 250 300 350 400 450 500
X
Frome the graph
dX
CV= d (2 ( YH ) .5)
Figure 1 : X (m) vs ()
282240
308260
= 0.875
50 100 150 200 250 300 350 400 450
0
20
40
60
Teoretical curves of
the jet trajectory
80
experimental curves
of the jet trajectory
100
120
140
Figure 2 : Theoretical and Experimental Curves of the Jet Trajectory Path
Figure 3 : The values of Y(exp) from the lab
Discussion
Discussion
that the actual flow rate QA is different from the
theoretical one, Q, which is corresponding to that the velocity of jet is
less than the velocity calculated because there is losses of energy
7
The coefficient of contraction indicates the losses of flow energy due to the change of
the orifice shape. Mathematically expressed as The ratio of the area of the jet, at venacontracta, to the area of the orifice
Typical values of coefficient of velocity, coefficient of discharge and
coefficient of contraction include 0.96, 0.62 and 0.64 respectively. As
it can be observed errors have been introduced within the
experiment most of them systematic as the values although precise
are not accurate. The experimental procedure has been observed
to be flawed in the following respect
There was a differences between the calculated ( theoretical) and measured
(experimental) due to the human error during experiment for many factors : such that
the apparatuses does not stand with level, the accuracy for determining the flow bath
has not done well.
What is the effect of the water height H on the jet trajectory path.
The effect of the water head on the orifice is the increasing of the flow energy such that
the more height of the water head the more velocity value will experiences the water
flow ejected by the orifice.
Conclusions
Experimental errors have significantly affected the values of the
coefficients. The precision of the results show that the errors are mostly
systematic as well as human errors during the insertion of gauge pins and
hence procedure wise it is deemed to be successful. The experimental
values for the coefficients are therefore not a good approximation of the
true value.
References:
[1] http://www.academia.edu/8952330/Flow_through_an_orifice
[2] http://uh.edu/engines/VelocityCoefficients.pdf
[3]Fluid Mechanics Report 3ed edition, (Nov.2015), King Faisal
University department of mechanical engineering, (Eng. Omar Osta).
