Hi, and welcome to another episode of
CARazy!
Today we're gonna be talking about....
drumroll please......aerodynamics!
While it is not necessary
for a car to run in its most basic form,
it is necessary for a car to run today,
what with fuel economy baselines and emissions regulations.
The same way that water vapor is just water, but the molecules are more loosely
packed,
air is essentially just liquid with its
molecules less tightly packed.
Have you ever tried
moving your hand under water? Easy.
What about clapping
underwater? Not so easy.
That is because drag is acting on your hands.
Drag is one of the most basic aerodynamic
forces.
If a car is square shaped a lot of air
pressure will build up in front
because the corners don't let air flow
freely.
At the same time low air pressure is
found
behind the car as the corners stop air
from going directly behind the car.
However, air always wants to be the same
pressure,
that's why vortices will yank air from
the sides
causing more low pressure pockets and
ultimately dragging the car back.
This is drag at work.The car will need
to use more energy
to move that much distance, and that
means it will
need to use much more fuel to travel
that same distance.
So we can conclude that a car will
always be more efficient if it's more
inclined
towards the most aerodynamic shape, the
teardrop, right? Not quite.
This is where the drag coefficient comes
in.
The drag coefficient is the
'effectiveness of a streamline
aerodynamic body shape in reducing air
resistance to the forward motion'.
The amount of drag any car or any object
has is determined by the car's velocity
(V)
Velocity squared multiplied by the drag
coefficient
multiplied by its frontal area. The aim
is to get as low a drag coefficient as
possible,
and an object's drag coefficient depends
on its overall shape,
size and surface roughness. The velocity
squared part of this equation
is why drag increases quadratically.
Drag
area
is the car's coefficient multiplied by
its frontal area
in square feet. But this equation also
means
that a bigger car with a lower drag
coefficient may have a bigger drag
area than a smaller car which has a
higher drag
coefficient. And the drag area
is what matters So even a car like the
Tesla Model X
which has a lower drag coefficient may
have more drag
than a smaller car like the Nissan 350z
which has the smaller frontal area. So,
despite it having a bigger coefficient
it has a smaller overall drag area.
Weight is also a factor in a car's fuel
economy,
but that is a topic for my engine video
so stay tuned for that!
As I was saying, that is drag
in all its complexity; how easily
air can flow over an object, here a car,
head on. However it is only
one of the basic aerodynamic forces. So
let me introduce you to another one
which car makers want to minimize. It is
called
lift. Yes, lift. We do not want lift of
course,
because a car lifting off the road would
be unfortunate.
So I will talk about down force now,
which is literally just negative lift,
and just the opposite of lift. Here's
the thing.
While you want air to flow freely across
your vehicle,
you want air to flow faster along the
bottom than at the top.
Why? Bernoulli's Principle. It states
that the faster moving a fluid is, the
lower its pressure,
and we have already learned that we are
swimming in an ocean of air.
This means that if we can make the air
flow faster beneath the car
than above, it will suck the car to the
road a.k.a
cause negative lift or down force.
Technically we're just rotating drag
counterclockwise
to use it to our advantage. This way
you can go around turns faster without
the car
lifting off the road. This
is how a spoiler works. It is essentially
just an airplane wing turned upside down
which causes it to make down force.
Airplane wings are curved on the top so
that the air takes longer to move over
it,
making it slower and forming vortices
that suck the plane upwards.
And now you know how an airplane wing works!
*celebratory noises yay*
Unfortunately, most downforce attachments
cause drag. It's like addition and
multiplication.
You can have drag without downforce but
you can't have downforce without drag.
But as always there are exceptions.
Canards and diffusers are some. There are
many other examples and principles as
well,
but I can't fit them into one video so
I'll post a part two next week covering
some more topics.
Comment below if you have any questions
related to this that you want me to
answer.
Okay then, CARazy out! For more amazing
content...
Staaaaay tuned!
