Hi, everyone, and welcome to this new class in the description of left and right and specifically
3D wings.
So we will start this class by stating the three most relevant ways in which the geometry of the whole
wing can impact the generation of lift and drag.
First, the live distribution around the win.
Second, the wing tip down wash and third wing configurations, so.
Leave this to Britain on a wing, as you can see shown in this image.
All off the lift force generated, but each cross-section of the wing will add up finally to the total
lift generated by the airplane wings.
However, as we can see, the distribution of the lift is not homogeneous and must be assessed when
designing an aircraft.
This type of aircraft shown here is actually a sail plane or a glider, which is just an airplane without
engines.
And as you can see, the lift for this airplane is more or less constant on all the wing, except for
the tip of the wing where the lift goes down to zero.
Also around the fuselage, the lift is also smaller.
As we saw previously, the lift generation capacity of a cross section, airfoil depends on the surface
of that cross section, which means that it is proportional to the core of the airfoil.
For the interior sections of the wing, the court is larger.
Therefore, the lift will be higher.
For those sections close to the wingtips, the cord will be smaller, same as the left.
So in other words, it would describe the lift generated by a cross section as a function of the position
of that airfoil, that cross section relative to a whole wing.
We will see that those parts which have a higher or bigger court will also have a higher lift.
So this is kind of the distribution of a standard wing for an aircraft which does not have engines below
the wings.
Note that the fuselage also has a slight lift.
However, as you can deduce, the lift of the fuselage is really negligible compared to the one off
the wing.
It is not to be expected that the fuselage will generate lift of the aircraft.
However, it can be convenient for the lift to not be equal to zero because in that case, if there's
some lift due to the fuselage, it can enhance the easiness of the flow around the whole aircraft,
providing a more stable flight.
The wings are therefore designed to produce lift, and the fuselage may produce just a bit of lift,
but is considered negligible when compared to the wings.
You can also see that the tail generates a negative lift in this case.
This is a design choice where the came off the airfoil of the tail is.
Put in this inverse ways, you know, due to the wings with respect to the wings.
So this would produce a negative lift, particularly also if the design of the tail also counteracts
the angle of attack.
So finally, the overall 3D live quite efficient.
And this is quite interesting is actually smaller than the 2D coefficient.
So it is cast for an airfoil that this would be the coefficient of lift curve.
And it can be seen that the 3D coefficient of lift is similar, but it does not increase as much with
the angle of attack.
And this is basically due to 3D effects of the wing, which do not allow for a perfect flow to go around
the whole aircraft, therefore reducing the efficiency of the flow to produce lift.
The second 3-D effect to be discussed is the so-called down wash effect or induced drag.
So this is a type of drug which is additional to the drugs of the aircraft that were already mentioned
and is actually really important in terms of wing design.
So let us describe this step by step.
So that it is clear.
OK.
High pressure is located below the wing of the aircraft.
It will always try to move from high pressure to low pressure.
And in this case, this will force a flow of particles around the wingtip.
This flow of particles creates a disturbance to the flow at the wingtip.
The wing, of course, is the fixed material that is there to separate the high and low pressure zones.
However, at the wingtip, this material separation is not there anymore.
Meaning that the particles will really move freely from one side to the other.
This is called the induced drug.
And the key concept here is that this disturbance of the flow around the wingtip would produce a significant
increase in the drag of the aircraft.
This disturbance, of course, can be described as a fluid vortex.
Note that there is a single point just at the wingtip where low pressure and high pressure are located
just above and below.
And this is clearly not stable, and this is the reason why this vortex is necessarily created.
If you're interested in getting a bit deeper into the physical phenomenon in this drug is also called
lift induced drug, and this is because this disturbance at the end of the wing produces a downward
flow just at the end, meaning that the flow is disturbed because there's a downward flow, right?
The angle of attack is therefore increased.
And as we know, if the angle of attack increases, then the lift increases.
And also, if the lift increases, then the drug increases, too.
So you can see that this because this this disturbance.
There will be a downward slope of the flow.
As a consequence of that, there will be an increase of the angle of attack as perceived by the wing
due to this disturbance, right?
And as a consequence of that, there will be a higher left and therefore a higher drag.
This is what we know as induced drag.
So here we have an example of what this industry looks like.
OK.
This is an Airbus A340.
And as you can see, a vortex of the flow is generated due to the difference of pressure on top.
And on the bottom of the wingtip.
Note also that this is symmetrical with respect to the airplane, with respect to its path, right,
and is generated over the wingtips.
So the question really is, how do we solve this?
The way to solve this problem is actually adding wingtips.
OK?
It's quite a simple solution to the problem.
Wingtips separate the high pressure with respect to the floor, to the low pressure surfaces at the
end of the wing.
By doing this, we put a physical material between the low pressure and the high pressure float, which
does not allow for the vortex to emerge.
This, as mentioned, will reduce the induced drag of the aircraft.
And this is why we always see wingtips on aircraft.
OK, so.
Now we can move to the next class.