aerodynamics
it's the promotion of
their or other gases
and of the forces acting on solid in
motion
relative to such air or other gases
relative wind
is the motion of the air with reference
who a body
it's maybe the result of moving there
and the stationary body
still error
and the moving
fair and body may be moving with
reference
correlative win
the algebraic
and airstream flowing fast reply
exerts upon it
through direction depends upon the angle
between the plane of the flight
and the direction of air flow
force may be analyzed it too
compliment force
which are folks live
and threats
let's act
at right angles to the relative wind
and drag acts parallel to the relative
win
if the plate is held in the heart of
awful airstream
in this matter
fifth opposed by the weight of the
and drag is opposed by the tensions on
the floor
if you don't go between the relative win
and the face of the place
is call the angle of attack
this angle may have any value from zero
ninety degrees
maybe either positive or negative
and therefore l
is any surface died to be projected
through the air
in order to produce for you
will dynamic reaction
airfoil which have been studied in views
vary widely
this is probably the most common type of
airfoil section
others are convex pallbearer offers
surfaced
concave all below
well through others are convex or both
relative thickness
and the curvature of airfoil
vary considerably
in general
aligned through an airport old leading
them to trailing edges
there's no notice
this is the case with an airport all
having
symmetrical double convex
in an airport which is convex
tougher surface
and concave below
the court correspond to the park of the
medium
and other airfoil
there's a lot of nablus
brought into contact with the lord
surface
to point
if you don't go between the court of the
pair foil
and the relative we have
is known as the angle of attack
of the airport
a wind tunnel is a device for testing
react
involved airfoil
and other aerodynamic
it usually consist
of a large
with the constricted
purple color produces airflow
and the honeycomb arrangement is placed
at one end
to insurance
careful
and drag of an air for a lot to be
measured
marvelous play spin the chamber and
supported by wired
why why run from the model through the
top of the tunnel
we'll balance
farm which is weighted
doors to maintain and
and compensate for other ports
from the leading edge of each wing
or why run
forward in the direction of
fully
and down to a bar on a flat
form faisal
a second pair of wires run vertically
downward
from the wing
to another scale
finally
uwire extends from the kneeled down to a
third gayo
in this way the model is
fended so that the various forces
exerted upon that
may be measured
the position of the models is observed
through thanking
with the air flowing at the desired
philosophy
dragonforce
is eager to the prom these wires
from flip
is measured as the actual lifting sports
from these wyeth
rear lift
as before
a farm that's life
total with
input from bob
and rear leg
here is one of the army's wind tunnel
that right field
it is nearly one hundred feet in overall
length
and at that
section is five feet in diameter
on the intake m
but you'd honeycomb arrangement of
mcilvane
break and be careful
for electric motors of four hundred
force
power each
french are concerned with that
through a promoters are shown here
there are two others inside the tunnel
the fans are twelve feet in diameter
adapt well blake
when driven at it
seven hundred rpm
they produce in there
speed up approximately two hundred miles
an hour in the tunnel
wind tunnel test
short i'll live
then drag vary with the angle of attack
of an air force
in general
uh... the angle of attack increases
lift and drag increase up to a point
where lift decreases abruptly
and drag becomes the principal component
this is an old time
the sprawling angle
from this angle to ninety degree
drag continues to increase
violent falls off
at ninety degrees the airfoil act like
the flat
it has maximum dragged
and negligible list
wind tunnel test have also proven that
for any given airfoil
and dragged very directly with the area
of the week
if the area is doubled
then drag are also double
lift and drag very directly as the
square of the velocity of the relative
win
if wind velocity is doubled
lift and drag our multiplied by four
lift and drag our directly proportional
to the density of the air faxing over
the air force
fared empathy is doubled
lift and drag there are also doubled in
value
expressed as an equation
if the people to coefficient which is
determined by the angle of attack
and shape of the airfoil
multiplied by the density of the air
multiplied by the area of the wing
multiplied by the velocity of the wind
drag equals the coefficient which is
determined by the angle of attack
and shape of the airfoil
multiplied by the density of the air
multiplied by the area of the wing
multiplied by the velocity of the wind
when an airplane is playing cards
awfully at a club
velocity
the forces acting upon it already
equilibria
the retarding force or drag
equals the propelling
or throught
must equal the total weights of the
airplane
therefore the list
and practically
served to determine
how much weight
therefore will live
under certain conditions
and how much
hours required
overcome with
total drag
of the airplane
the air pressure at various
points on the airfoil
measured in order to determine the
airfoil deficient
or it suitability for a given perfect
the measurements are made by building
into a model airfoil
small copper tube
which are field
the field
them from the bottle
we're pressure measuring device
outside the problem
the device is called
from obama's ur
the figure illustrates the principle of
operation
the liquid the
through around the reservoir
will be at the same level
as long as the pressure involved
to lab reservoir party
if by any means
but does that
wondered for example
the pressure in the field with him
the liquid in force into the reservoir
lowering the level in the field
pressure in the field
it deeply
liquid rises above the level of of the
merciful
in a divide such as this
if the liquid in the field with
subjected to varying
level will rise above
or fall below the level of the liquid
repertoire
turkey decrease
reading of liquid level
provides an accurate means of
determining pressure difference
additional too
maybe at
each connected to a different value
and each will indicate
that records accurately
regardless of pressures in the other
operating on these print
east bank of my mother to review to
determine pressures on an airport
because all too
are at the same pressure
levels in the field
for test purposes
each muhammad refueled with connected to
a different point on the purpose of the
airport
the majority of the
are located only
leading-edge
and offer surface
relatively few are placed on the low sir
of course this
is only a schematic representation of
the connection
in actual fact
who will be drawn from the man on the
third
through an opening
and inside of the airfoil for the past
atmospheric pressure reputedly taken
as the reference level
pressures above atmospheric are called
positive
goes the low atmospheric are called
negative
actually these values are pressure
difference
with reference to the absolute spirit
with reference to
absolute zero
all pressures are necessarily possible
the model airfoil
in the test
of the windpipe
supported by wired
will transmit it
and drag portland to the states
to which connects to the test
are fast through an opening in the
tunnel walls
and connected to the mohammed her brain
thermometers
being it equals pressures
are at the same level and are connected
to the airport
not from each manometer q
there is a direct
to a definite
on the surface of the model airport
paul is now ready for the past
and the engineers meet the tunnel to
take up positions where they can observe
them
measure reaction the from the airport
the motors which drives the fan
in the tunnel
the model airfoil its objectives of the
famed conviction
with within copper in actual flight
through a medium of the things that that
and pressures along with references are
thought
as would be met on the plane
thermometer q
tell the story
levels fluctuate likely
renewed variations in here
or density of her
but the ratios are calm
and the position of the liquidity in the
field
shows both positive and negative value
for the airport
the tubes are photographed
to assure simultaneous readings of all
too
at the photograph is used by engineers
the plus a pressure cooker
in this manner a diagram is constructed
shorten the nature and the computer
pressures
over both surfaces of the wing
at varying times over the past
positive pressures are shown in black
negative in bright
at zero degrees
there is a small bobo
positive pressure directly upon the
leading edge
another area of
imposes the trailing edge
and extend forward about one quarter
portland
along the lower surface
elsewhere the pressures are negative
as the angle of the fact is increased
the positive pressure bulb
moves lower down on the leading ads
and back along the lower surface of the
wings
and closing the trailing
the negative pressure distribution
remain fundamentally unchanged
although its values are greatly
increased
that diagram indicates
at the wing has begun to exerted
considerable list
increasing the angle of attack
still further
pressure distribution very little
although there is a must
changing values
particularly along the upper surface
where negative pressures are now
addressing a powerful list
the wing is null proceeded
stalling and
pressures that changed very little in
eva distribution
the negative values however
have increased
especially at the leading
by further increasing the angle of
attack
pressures remained practically unchanged
in both value and distribution
but the value of negative pressure
continues to increase
at this time the love attacked
the wing as well practiced throwing
angle
yet the positive pressured
show a little indication of change
with the negative pressured
the greatest changes noticed that the
leading edge of the wind
where they are you continue to explode
and the outline of the pressure area
is extremely irregular
increase angle of attack
bring no important change in positive
pressure value
part distribution
but the negative pressure area intending
to equalize it does
over the entire offers surface of the
way
at this time the love the fact
before put different
disappeared completely
and an area of nearly
equal negative pressure
at the entire offers surfaced
positive pressure areas
still show no important to me
another increase in the angle of the
fact merely results
in increase value
distribution remaining almost the
payment before
at this final angle
pressures have reached still greater
values without any appreciable change in
distribution
it might appear from the start of them
benefits angle of attack uniform
pressure distribution over the upper
wing surface
would be desirable
however
above the following angle
result and therefore saxton budget
direction
at the dragons this large component
than airfoil at rest
still here
that atmospheric
pressure over a simple answer
it has been shown that airfoil derive
their lives
from the pressure differences acting
upon their surface
the negative pressure difference upon
the offers surfaced
normal angles of the fact being the
major component
now let us see what happened to
pressure values and distribution
that's negative angles of attack
from zero degrees
the angle is decreased
reply to make it better
the positive pressure both on the
leading edge
practically empty
the negative pressure on the upper
surface of the wing showed little change
however the negative
structures along the lower surface
begin to increase at the leading it
further increases in this area
company bribery
preferable
or the only difference is
which are readily observable as the
angle of attack you
for thirty three
the angle of attack
or boiled with
film to be the acute angle between the
court of the airport
and the relative win
the angle of attack of the airplane as a
whole
should be acute angle between the
longitudinal axis of the airplane
found a relative with
the difference between these two angles
conference for any given airplane
that is call the angle of him for that
although the angle of the fact is
constant for any given wind tunnel set
an actual flight
the angle of the fact of the airfoil
ties with changing attitudes
speed of the airplane
consider the case
of an airplane flying paws awfully
at a small positive angle of attack
at the controls are set
support the airplane into a dive
the angle of attack decreases
decreases
sentiment that a few of the weight of
the airplane is opposed
as a result of of lift and drag
as the flights approaches the vertical
speed increases until the terminal
velocity is reached
so-called particle dot
in that condition lifted zero
and the weight of the airplane
proposed by drag alone
in pulling out of the time
the angle of attack but the increase
during this maneuver
maintained several times
value typically
increases
produces acceleration
which in turn produces the curb
like that
