Fluid friction
:Introduction
When a fluid is flowing through a pipe, it experiences some resistance due to which
some of energy (head) of fluid is lost. Energy loss through friction in the length of
pipeline is commonly termed the major loss (hf) which is the loss of head due to pipe
.friction and to viscous dissipation in flowing water
The resistance to flow in a pipe is a function of the pipe length, pipe diameter, mean
velocity, properties of the fluid and roughness of the pipe (if the flow is turbulent), but
it is independent of pressure under which the water flows. Friction head losses in
straight pipes of different sizes can be investigated over a range of Reynolds' numbers
from 103 to nearly 105, thereby covering the laminar, transitional, and turbulent flow
regimes in smooth pipes. A further test pipe is artificially roughened and, at the higher
.Reynolds' numbers
:Purpose
To determine the relationship between head loss due to fluid friction and velocity for
.flow of water through smooth bore pipes
:Apparatus
.Fluid friction apparatus(pipes,valves,fitting,elbows) .1
Hydraulics bench to supply water to the fluid friction apparatus (the flow of water .2
.can be measured by timed volume collection)
Figure 1: Fluid friction apparatus
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Fluid friction
:Theory
:The head loss due to friction in a pipe is given by
l u2
lh= f
d 2g
:Where
l: is the length of the pipe between tappings(m).
d: is the internal diameter of the pipe.
u : is the mean velocity of water through the pipe( m/s).
g : is the acceleration due to gravity (m/s2).
f : is pipe friction coefficient.
:The Reynolds' number, Re, can be found using the following equation
duρ
R=
e
μ
.Where μ is the molecular viscosity (1.15 x 10 -3 Ns/m2) and ρ is the density (999 kg/m3)
-.the value of may be determined by using a Moody diagram as shown below
Figure 2
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Fluid friction
:Procedures
Prime the pipe network with water. Open and close the appropriate valves to obtain .1
.flow of water through the required test pipe
Take readings at several different flow rates, altering the flow using the control .2
. valve on the hydraulics bench
Measure flow rates using the volumetric tank .For small flow rates use the .3
measuring cylinder. Measure head loss between the tappings using the portable
.pressure meter or pressurised water manometer as appropriate
.Obtain readings on all four smooth test pipes .4
.Measure the internal diameter of each test pipe sample using a Vernier calliper .5
: Results and Calculation
: The following table shows the results of the experiment
V,m3 0.005 0.005 0.005 0.005 0.005
t,s 43.83 44.48 39.49 32.86 37.07
m, 0.675 0.672 0.682 0.705 0.680
hc
hd m , 0.577 0.582 0.568 0.565 0.574
: The calculation of the first result
At
V = 0.005 m3 , t = 43.83 s , d = 0.0175m ,A = 2.404*10-4 m2
V
Q=
t
500.0
0.000114m3/s Q=
=
38.34
Q
u=
A
411000.0
u= 5474
=.0
−4
404.2 ∗01
duρ
R=
e
μ
999
5474.0
∗ 5710.0
∗
R=
e
51.1 ∗01 − 3
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Fluid friction
4.3127
R=e
noitcirF
fℜ( =) rotcaF erugif
¿ − 2− ta ℜ
6800.0
f
=
l u2
lh= f
d 2g
6800.0 ∗1 2
5474.0
∗
5710.0
lh= 6500.0
= m
2∗
8.9
H = hc-hd
H =0.675-0.577 =0.098m
:All results are shown in the table below
V(m3) t(s) Q(m3/s) A(m2) U(m/s) Re f hc(m) hd(m) H,m hl,m(eq)
0.005 43.83 0.000114 0.00024 0.474518 7213.707 0.008572 0.675 0.577 0.098 0.540444
0.005 44.48 0.000112 0.00024 0.467584 7108.291 0.008604 0.672 0.582 0.09 0.526699
0.005 39.49 0.000127 0.00024 0.526668 8006.502 0.008352 0.682 0.568 0.114 0.648632
0.005 32.86 0.000152 0.00024 0.632931 9621.934 0.007976 0.705 0.565 0.14 0.894711
0.005 37.07 0.000135 0.00024 0.56105 8529.182 0.008221 0.68 0.574 0.106 0.724539
.The relative between the H and u( shown in figure 3)-
0007.0
0006.0
0005.0
0004.0
0003.0
m,h
0002.0
0001.0
0000.0
59.0 9.0 58.0 8.0 57.0 7.0 56.0 6.0 55.0 5.0
s/m,u
Figure 3
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Fluid friction
.The relative between the logH and logu(shown in figure4)-
0
hgol SV ugol
0 - - -
Figure 4
: Discusion and Conclusion
Of the observations during the experiment should drain tubes from the air because the
presence of air inside the tubes cause an error in the results and to avoid entering the
.air should not open the entring valves before exit valves
أي انه الفقد للطاقه في الجريان, نالحظ أن كلما زاد التدفق تزداد سرعة المائع ومن تم تزداد قيمة الفقد في الطاقة
التغير,الصمامات, وايضا هناك عوامل ثانويه ومنها الوصالت, االضطرابي أكبر منه في حالة الجريان الطبقي
.الكوع,في االقطار
: References
www.scribed.net
.fluid mechanics,www.iguaza.edu,eg(13-6-2018),5:42pm
5 Fluid lab mechanics
