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ECOR 2606 Assignment #3
As a liquid moves through a horizontal pipe, the pressure drops due to friction between
the liquid and the walls of the pipe.
In order to calculate the actual pressure drop, it is
necessary to somehow determine the friction factor (
f
).
One possibility is to use a
Moody chart (see the chart supplied).
The inputs are R (the Reynolds number for the
flow) and the relative roughness of the pipe (
ε
/D, where
ε
is the roughness of the pipe
walls and D is the diameter of the pipe).
If there is no line on the chart for the particular
ε
/D of interest, interpolation is required (one must imagine the required line).
Otherwise
use of Moody charts is straightforward.
The value of R is entered at the bottom of the
chart and the value of
f
is read from the left hand scale.
Moody charts are based on the Colebrook formula for
f
.
They were once the primary
source of friction factor information, but today, with computers and calculators at our
disposal, it is just as easy (as much more accurate) to use the Colebrook formula directly.
The Colebrook formula is given below.
If
R
,
D
, and
ε
are all known, it is possible to
solve for
f
(the only unknown).
f
D
f
R
51
.
2
7
.
3
log
0
.
2
1
Write a function called
Fb
that, given the values of
R
,
D
(in m), and
ε
(in m), uses a
bisection search to find
f
.
Reasonable initial bounds can be generated by applying the
Blasius formula for smooth pipes (
f
= 0.3164 R
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 Spring '10
 saas

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