To complete our three-part mini-series on various aspects of aerodynamics I’m going
to look at a few common aero devices.
I’d suggest making sure you watch my previous two videos as I’ll be assuming you know
the basics as I rattle on through Looking at the rear wing, there are two devices
on the endplates that all the cars use now.
One is these little slots, or louvres.
The other is this cut out, behind the actual wing itself.
What’s the deal with these?
First let’s understand why endplates exist in the first place.
Without them, you’d get big old vortices generated by the high pressure air spiralling
over into the low pressure air below.
I talked a big game on vortices in the last video but there is a negative by-product to
them – drag.
What’s happening is this.
Before the vortex is generated, the air is going straight backwards.
In generating a vortex you’re taking some of the backwards-going energy and turning
it into sideways, spiralling energy.
That is, the air is losing some of its backwards speed – you’re slowing it down.
And if you slow the air down, the air slows you down.
That’s drag.
So to reduce vortex generation they simply bang massive panels on the edges of the wings
– the end plates – and this stops the air spiralling over and creating vortices.
But.
The air inside the endplates and over the wing – here - is much higher pressure than
the air outside the end plates here.
So at the tips here the high pressure air still rushes over the top to find the low
pressure air., causing wing tip vortices, which are a bit draggy.
To combat this, these louvres allow the high pressure air to mix slightly with the air
outside the endplates and reduce the pressure difference.
And to explain the cutout at the back: realise that now this flow of air outside the endplates
is actually a higher pressure than the air under the wing inside the endplates.
So this generates a little vortex itself, but as it’s spinning in the opposite direction
to the wingtip vortex, it neutralises its spin and reduces its effect.
Moving below the rear wing now, let’s look at Diffusers.
The diffuser is the big scoop shaped thing at the rear of the car floor.
To understand the diffuser, let’s look at the car from the side and cut everything else
away.
Now we can see the diffuser helps the underfloor of the car become a lot like the underside
of a racing wing.
The air rushing under the car is crammed into this tight space between the car floor and
the track.
The diffuser, like the exit curve of a wing, sucks the air into this low pressure void
here and this suction essentially continually accelerates the air through the tight undercar
space.
As we learned previously: squeezing and accelerating air massively reduces the pressure of that
air and this low pressure area sucks the car down towards the ground.
This is a huge downforce generator known as the ‘ground effect’.
The shape of the diffuser works hard to smooth out the air flow as it transitions from fast,
low pressure to the ambient air behind the car.
In fact, often the whole car is raised from at the back (increasing the angle of what
is called the car’s rake) to smooth out this diffusion process right along the car.
These vertical strakes also work to guide the air smoothly out of the back of the car,
increasing the efficiency of the diffuser and reducing turbulence.
Now let’s look at Bargeboards.
There’s a lot going on with bargeboards – you could spend an hour trying to unpick
all the nuances of any individual bargeboard ¬ but I’ll try and keep it simple.
Firstly, they work to deflect and shape the path of different air flows.
Along the side of the car, you’ve got nice smooth air flowing along the body, you’ve
got this big vortex powering out of the front wing and you’ve got dirty air from the tyres,
all messy and horrible.
The vortex is something of an impenetrable high energy wall, so part of its job is to
keep the messed up tyre wake away from the nice smooth airflow running along the body.
The bargeboard helps coax the vortex around the body of the car and allows the clear air
to pass on through to places like the air intake and around the body.
Secondly, the shape and intricacies of the bargeboard and the turning vanes (which are
just elements similar to the bargeboard but situated further up the nose) create their
own vortices which help seal in the fast, low pressure air under the body, stopping
it leaking out, which would reduce its effectiveness.
Older cars use to have physical seals at the bottom of the car called skirts but these
were banned long ago when ground effect was getting too strong.
So bargeboards and turning vanes direct the complex flows of air and generate a vortex
seal along the base of the car to aid the air travelling to the diffuser.
And finally, let’s explore the S-Duct.
On some cars you’ll be able to see the entry point of the s-duct, visible as nostrils on
the nose of the car.
And on most cars you’ll see the exit point – a letterbox opening on the bridge of the
nose, just in front of the suspension.
The s-duct channels air from under the nose up to the top surface of the nose, here.
This solves two problems at once.
Problem the first: The boundary layer – the layer of air slowed down by frictional forces
with the cars surface – can buildup here, causing drag and pressure problems.
Allowing it somewhere to escape can relieve the build up.
Problem the second: the slope of the nose can cause air flow separation, which as we
know is inefficient and draggy.
Blowing air across the surface energises its boundary layer here and keeps the air smooth
and attached to the nose as it travels down the body.
Overall it’s a small effect but a net gain worth exploiting.
Look all over any given F1 car and you’ll see lots of little devices all guiding air,
affecting pressure differences or trying to minimise aero effects.
Hopefully with the help of these three videos you’ll have a better foundation on which
to understand all these bits and bobs all over the cars, have more of an idea of the
effect of new aero developments in future, and understand all the jargon that TV presenters
and articles use when talking about aero parts.
This isn’t the last I’ll talk about aerodynamic parts and effects in future as there’s seemingly
no end to weird little exploits the engineers will invent to make
the air bow to their whim.