TOPIC: Functions & Using loops and indices
READING:
5.12
WRITTEN:
5.1, 2, 27
ANALYSIS:
In analyzing experimental data, we often wish to fit a curve to data which may
contain experimental error. We can use the method of Least Squares to fit the "Best" straight line
to the set of data. Given a set of N data values: { (x
i
, y
i
) } The equations for finding m & b for
the "best straight line y = mx + b are given by
:
2
2
AB
NC
AC
BD
m
and
b
A
ND
A
ND


=
=


where
2
1
1
1
1
,
,
,
N
N
N
N
i
i
i
i
i
i
i
i
i
A
x
B
y
C
x y
D
x
=
=
=
=
=
=
=
=
∑
∑
∑
∑
APPLICATION
: A 1:32 model of a F117 Nighthawk was placed in a wind tunnel whose free
stream velocity was 50ft/s and the coefficient of lift C
l
was measured as a function of the angle
of attack. This experimental data is then fit with a straight line which can be used to predict C
l
for other angles of attack. (the coefficient of lift, C
l
,
is a
non dimensionalized variable. C
l
= L/
(.5
ρ
v
∞
A) where
ρ
is the density of air,
v
∞
is the free stream velocity of the air in the wind tunnel
and A is the area of the wing surface.)
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '07
 Hayes
 Regression Analysis, Aerodynamics, Greek alphabet, Airfoil, Angle of attack

Click to edit the document details