Rear wing – Technical Analysis

rear wing of mercedes w11

Previously, I have written a technical analysis of the diffuser. This time we are looking at the rear wing. The diffuser and floor are responsible for about 40% of cars downforce, and therefore are the most important part of the car, but the rear wing is the second most important part, creating about 30% of said downforce. 

Written by Ive Bauk, Edited by Sam Stewart

Firstly, the rear wing is the most generic aerodynamic design. Its main purpose is to send the air upwards and therefore increase downforce. 

This is a default wing design, rendered in CFD (Computed Fluid Dynamics) simulations. The wing is rendered in this fashion in order to emphasise the changes efficiently.  

So as it seems, this wing will push the air upwards and create downforce, but you can also see that it will create huge amounts of drag behind, therefore slowing the car down. 

Here is a simulation of the airflow of the rear wing.

Now, as you can see, air is moving downwards after the wing meaning it is doing exact opposite of what we want. 

This picture shows the reason why the air goes downwards, as you can see air is avoiding the wing and trying to find the fastest and most efficient way to pass by. Now after the air avoids the wing successfully, it has to fill in the void behind the wing. This area, in comparison, is huge. This is why the air moves down.

So how did the teams solve this issue? Well, they found a solution in the so-called Coanda effect. My explanation for it would be: imagine a drop of rain moving down a leaf.

When a droplet of rain falls on the leaf it starts moving down the leaf due to the gravity. 

When we rotate a leaf like this, rain will still keep following its line for some time, but eventually gravity will be stronger than friction, and water will fall from the leaf. 

If we take an example of a big amount of water falling down the leaf, we will see that the water stays near the leaf in the bottom part but it gradually decreases as the gravity increases and friction decreases.

But what does it have to do with the F1? To see this, we have to turn the leaf once more.

Upon turning the leaf and subsequently changing forces from gravity to drag, you get something that looks and acts similar to an F1 wing. 

So, let’s go back to our non efficient rear wing. Now that we’ve learnt what the Coanda effect is, we know we want to make it stronger and more efficient on our wing. 

F1 designers have come up with the solution for this issue too. They introduced a small slot in the middle of the wing which makes the Coanda effect stronger. This means that the effect is strong in the bottom part of the wing, then slowly reduces until it reaches our hole and then it reduces again.

Render of rear wings adapted to the Coanda Effect

As you can see, most of the air is moving up whilst some of it is caught in the turbulence, low pressure area where air moves quite randomly. 

But again, after seeing final footage of this wing I realized that it creates way too much drag on the sides. 

This is a picture from underneath the wing, you can see that there is a lot of turbulence behind the wing but not only that, even the air flowing around the turbulent area is very low pressure (light blue colour).

The final part of the rear wing that aids drag is the endplates on the sides of the rear wing.

Here is the final design of the rear wing. Endplates have been added along with 3 slots in order to assimilate air pressures on both sides of the endplate. As you can clearly see by the colouring, inside parts of the endplates have much higher pressure even though the slots have been added. 

The most important difference is that the air isn’t moving too wide as it was in last 2 experiments, secondly, pay attention to vortices that are being created of the sharp edges of the endplates, they are technically speaking turbulence and thus increase drag a but, but more importantly, they direct the air and help the increase of downforce. Also you can see air moving through the slots. There are usually more slots on the rear so they have a bigger impact but I didn’t add them all firstly because this wing is smaller and secondly because they aren’t as important in this experiment.

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