Sauber C32 Ferrari

[shelly]

Also flow isn't consistent on the rear wing. The middle has the roll hoop and engine cover disrupting the flow. Something to consider.

+1 If you look at the mclaren 2011 picture you will notice how the central part of the wing is twisted to get a good angle of attack in the different flow condition due to the presence of the airbox. in 2012 all cars had a raised central leaind edge. Sauber may have tacked the same issue in a different way this year.

[Randomness]

To both the guys who made the rear wing CFD simulations. While the results are a good indicator of what is happening, especially the DRD one, they are very vague. Arthur Craft you state that

The wing is less efficient, on itself, than a normal wing. In another words, it gives less downforce for the same drag and vice versa

But that is likely false. You cannot give this information because your CFD model is not relevant to what is actually happening. As a wing, it does provide less downforce. But as a car component, it probably won't. The rear wing is subject to the flow from the front wings, over the body of the car, around the airbox etc etc. This means that the air reaching the rear wing will not be as clean as you are simulating. What you are likely to find is that due to the low pressure behind the airbox/bodywork of the car, there is likely to be a higher energised flow reaching the centre of the wing than the outside edges. SO, by making this part deeper, they are producing more downforce than your simulation is claiming.

I'm not criticising your work I like the fact that you make the effort to bring CFD models into this, but you can't make claims about what is happening because your model doesn't provide any tangible evidence to support your claims.

[ringo]

Guys, this is quite an interesting issue that I had in my mind since I first saw Sauber's new rear wing. I wondered the effect of such central section

Forget about the DRD effect for a moment, Sauber was also using it even when not running the device's pipe

I asked one of the members(amouzouris, a great guy who have an awesome technical blog btw) to run CFD tests to see the efficiency of C32's new rear wing, the results are here:
http://www.f1technical.net/forum/viewto ... =6#p413338

The wing is less efficient, on itself, than a normal wing. In another words, it gives less downforce for the same drag and vice versa
http://farm9.staticflickr.com/8235/8498 ... c290_b.jpg
To bring some numbers, the old wing, the one without the curved central section, gives around 15% less drag, for the same downforce

Some CFD shots of both, just for curiosity:
A wing more like the old design
http://farm9.staticflickr.com/8380/8498 ... 2545_b.jpg

A wing more like the new design
http://farm9.staticflickr.com/8525/8497 ... d31d_b.jpg

Old like
http://farm9.staticflickr.com/8249/8497 ... cff8_b.jpg

New like
http://farm9.staticflickr.com/8230/8498 ... 71fb_b.jpg
We must now look to where this is benefiting the overall car's performance, as obviously nobody would be using it if it wasn't benefitial in some way

That kind of wing is more efficient. I guess it wasn't modeled accurately. wing profiles are hard to model any way because F1 wings are very unique; they arent like plane wings so data on them is almost non existent for the public.
A good indicator of this wings purposes is the wings used in canada by Williams, and also the W shaped wing by Renault. It's overall downforce is probably less, but it produces smaller upwash and vortices at the end plates due to smaller profiles. It loses some downforce on the ends and makes back some of it in the deeper midspan.
The mid span needs the monkey seat to assist the air flow underneath as well, because of it's high camber.

[ringo]

To both the guys who made the rear wing CFD simulations. While the results are a good indicator of what is happening, especially the DRD one, they are very vague.

I just wanted to model it correctly first. If it was modeled incorrectly and i spewed out some numbers, then that would be misleading. I think it's best to continue in the DRD thread.

http://www.f1technical.net/forum/viewto ... =6&t=14703

[amouzouris]

To both the guys who made the rear wing CFD simulations. While the results are a good indicator of what is happening, especially the DRD one, they are very vague. Arthur Craft you state that

The wing is less efficient, on itself, than a normal wing. In another words, it gives less downforce for the same drag and vice versa

But that is likely false. You cannot give this information because your CFD model is not relevant to what is actually happening. As a wing, it does provide less downforce. But as a car component, it probably won't. The rear wing is subject to the flow from the front wings, over the body of the car, around the airbox etc etc. This means that the air reaching the rear wing will not be as clean as you are simulating. What you are likely to find is that due to the low pressure behind the airbox/bodywork of the car, there is likely to be a higher energised flow reaching the centre of the wing than the outside edges. SO, by making this part deeper, they are producing more downforce than your simulation is claiming.

I'm not criticising your work I like the fact that you make the effort to bring CFD models into this, but you can't make claims about what is happening because your model doesn't provide any tangible evidence to support your claims.

I am not basing the argument that a wing with the DRD neck attached will produce less downforce from CFD work, it is based on theory (actual aerodynamics theory) I have never made claims that my CFD tests represents what is actually happening and I have more than once used the words 'to give us an idea'. From what I can see neither Ringo made such claims. Also, have a second look at your theory about the airflow behind the airbox.

Furthermore, I don't know what is the computing power of Ringo's computer, but it takes too long for a full car simulation on my computer at least, not to mention it is trying to kill my computer every time I attempt one!

[Randomness]

Directly behind the airbox there is low pressure which is why the air flowing around it gets pulled in, and as a result more air flow reaches the centre of the wing than the outside. You need look no further than an airfoil to understand this.. For my FYP at univeristy last year it took 3 hours and 40 minutes to do a full simulation of the sidepods/airbox backwards to get a full CFD model. I'm not saying that this is what should have been done, and I appreciate that you are saying "in theory." But I'm saying not to draw conclusive fact or to try and make points based on a vague CFD model. I only have a laptop, the CFD compuers I used belonged to the university and I can't afford my own, so as I say I appreciate the effort other people put in. My only meaning was to take the results with a pinch of salt, especially when the rest of the car is not present.

(Additional point which is why this post is edited.)

We are not talking about the DRD wing here, we are talking about the curved wing vs the flat wing. The reason for my post is that whoever it was claimed that the wing produced less downforce for the same drag. But this is simply not true. That was the point. The curved wing collects more air in the centre of the wing. Because this is where the air flow is stronger. On that CFD simulation, lacking an airbox, the air reaching the wing is linear. Which means that it renders the test pretty much useless, as the wing will never be subject to airflow that is not interrupted by the airbox.

[hollus]

...as a result more air flow reaches the centre of the wing than the outside...

You are basically saying that because there was an obstacle in the way of that air, that air is now better/stronger/faster... not sure that makes sense, we should be placing obstacles everywhere.
What do you mean exactly by "more flow". More mass, higher speed air, better angle of attack, something else?

[amouzouris]

Directly behind the airbox there is low pressure which is why the air flowing around it gets pulled in, and as a result more air flow reaches the centre of the wing than the outside. You need look no further than an airfoil to understand this.. For my FYP at univeristy last year it took 3 hours and 40 minutes to do a full simulation of the sidepods/airbox backwards to get a full CFD model. I'm not saying that this is what should have been done, and I appreciate that you are saying "in theory." But I'm saying not to draw conclusive fact or to try and make points based on a vague CFD model. I only have a laptop, the CFD compuers I used belonged to the university and I can't afford my own, so as I say I appreciate the effort other people put in. My only meaning was to take the results with a pinch of salt, especially when the rest of the car is not present.

(Additional point which is why this post is edited.)

We are not talking about the DRD wing here, we are talking about the curved wing vs the flat wing. The reason for my post is that whoever it was claimed that the wing produced less downforce for the same drag. But this is simply not true. That was the point. The curved wing collects more air in the centre of the wing. Because this is where the air flow is stronger. On that CFD simulation, lacking an airbox, the air reaching the wing is linear. Which means that it renders the test pretty much useless, as the wing will never be subject to airflow that is not interrupted by the airbox.

I completely agree about taking the results with a pinch (or even two) of salt. I know we are talking about the two wing types here. The dished, spoon wing or whatever else you want to call it, is used to compensate for the exact disturbance you described behind the airbox, along with other reasons which I am not going to get into now. The flow behind the airbox is not 'stronger' it is the exact opposite. And as you said, you only need to look at an airfoil to know this...

edit: here is the actual 'proof' (this was a full car test):

[ringo]

We are not talking about the DRD wing here, we are talking about the curved wing vs the flat wing. The reason for my post is that whoever it was claimed that the wing produced less downforce for the same drag. But this is simply not true.

You could be correct here.

That was the point. The curved wing collects more air in the centre of the wing.

I don't think this is correct. Maybe i'm misinterpreting your statement.
Are you saying that in the middleof the wing there is better airflow approaching the from upstream?
If you are saying this then i don't think that is the case. How can an obstructed flow with lower energy, coming off the air box, be stronger than free stream; keeping in mind that the outer parts of the wing have unobstructed flow coming from upstream?

Because this is where the air flow is stronger.

IMO it's not stronger here. It's stronger at the end plates. There is reasonable evidence to suggest the middle has a weaker flow. I could be wrong, but you have to show us some reasoning to support your case. I can use some images from 2009 season to demonstrate.

On that CFD simulation, lacking an airbox, the air reaching the wing is linear. Which means that it renders the test pretty much useless, as the wing will never be subject to airflow that is not interrupted by the airbox.

I see your point about the airbox making things less linear, but i would suspect the flow to be weaker in the middle and not stronger. There is a difference, but the wing is so relatively far away from the airbox that it is a minuscule difference.

[Randomness]

I don't know how to copy that above image. The one posted with the pressure zones, but it is going to help me explain my point

Behind the airbox there is an area of low pressure. When there is low pressure, fluids will automatically move to it as if it is a vacuum. It is the natural order of things.

I am not saying that an obstacle creates better airflow, but examine the behaviour of air bout a winglet. The air is pushed around the obstacle because of the area of high pressure in front of it.

It will then re-join behind it because of the area of low pressure, and the flow will resume at a slightly SLOWER speed because of the drag.

However, an airbox is not a winglet. It swallows a lot of air, which means that the air that goes around it, finds an area of low pressure (like a winglet.) But a smaller volume of air to fill the void. This causes acceleration of the air. Naturally, there will be drag due to the surface of the bodywork, and the air is by no means clean. But a lot of the air that is "pulled in" by the low pressure is clean, and slightly faster than the air around it. It is like creating wind, but on a much smaller scale. Wind is created when there is high and low pressure, and the air escapes the high pressure, into the low pressure areas. This causes acceleration. So, the air in the direct wake of the airbox where the flow re-joins, is accelerated. Because the air is moving from the normal atmospheric pressure, to the area of low pressure behind the airbox (as the image above demonstrates perfectly. Amazouris. You say the flow is not stronger, but that image is actually showing an area of low pressure. Not the speed of the fluid.

[hollus]

So you are suggesting that by the time it reaches the rear wing, the air from around the airbox hasn't had time to fill in the partial void from the airbox yet, it is still rushing towards it, and hence it has higher speed? Wouldn't this rush be mostly perpendicular to the direction of movement of the car?
I'd love to see an example of that.

By the way:
How to post a picture

You can also click the "Quote" button up-right from the post you want to copy from, and you'll get a pre-formed posting screen where you just need to decide which parts of the post (including quoted image) to keep.

[Randomness]

How to post a picture

You can also click the "Quote" button up-right from the post you want to copy from, and you'll get a pre-formed posted screen where you just need to decide which parts of the post (including quoted image) to keep.

Thank you for your help.

[ringo]

Amazouris. You say the flow is not stronger, but that image is actually showing an area of low pressure. Not the speed of the fluid.

yes his image is pressure and not speed, but never the less, you are ignoring the internal energy.
There is a loss of energy in your scenario mentioned above. The air wont be faster, and it wont be of a better quality.
You are ignoring a lot of things. If he was to display speed, there would be a drop in speed as well as pressure.
Classically there is the assumption of no energy transfer. Not the case in the simulation and reality.

[amouzouris]

I don't know how to copy that above image. The one posted with the pressure zones, but it is going to help me explain my point

Behind the airbox there is an area of low pressure. When there is low pressure, fluids will automatically move to it as if it is a vacuum. It is the natural order of things.

I am not saying that an obstacle creates better airflow, but examine the behaviour of air bout a winglet. The air is pushed around the obstacle because of the area of high pressure in front of it.

It will then re-join behind it because of the area of low pressure, and the flow will resume at a slightly SLOWER speed because of the drag.

However, an airbox is not a winglet. It swallows a lot of air, which means that the air that goes around it, finds an area of low pressure (like a winglet.) But a smaller volume of air to fill the void. This causes acceleration of the air. Naturally, there will be drag due to the surface of the bodywork, and the air is by no means clean. But a lot of the air that is "pulled in" by the low pressure is clean, and slightly faster than the air around it. It is like creating wind, but on a much smaller scale. Wind is created when there is high and low pressure, and the air escapes the high pressure, into the low pressure areas. This causes acceleration. So, the air in the direct wake of the airbox where the flow re-joins, is accelerated. Because the air is moving from the normal atmospheric pressure, to the area of low pressure behind the airbox (as the image above demonstrates perfectly. Amazouris. You say the flow is not stronger, but that image is actually showing an area of low pressure. Not the speed of the fluid.

I interpreted your post and the use of the word 'stronger' as the wing directly behind the airbox will produce more downforce, which is clearly not the case as can be seen from the pic I posted above, look at the middle of the wing.

Allow me to say that you are wrong..the air behind the airbox is certainly not going to be accelerated. Below you can see a velocity cut plot:


Anw..the conversation has gone wildly off topic...

P.S. Please write my name correctly

[Randomness]

Amazouris. You say the flow is not stronger, but that image is actually showing an area of low pressure. Not the speed of the fluid.

yes his image is pressure and not speed, but never the less, you are ignoring the internal energy.
There is a loss of energy in your scenario mentioned above. The air wont be faster, and it wont be of a better quality.
You are ignoring a lot of things. If he was to display speed, there would be a drop in speed as well as pressure.
Classically there is the assumption of no energy transfer. Not the case in the simulation and reality.

There would be a loss in speed and energy from the air that had come into contact with the bodywork yes. But for the air that is pulled in that did not come from the bodywork, the air would be accelerated due to the shift to low pressure. Because low pressure zones accelerate fluids.

Bernoulli's principle can also be derived directly from Newton's 2nd law. If a small volume of fluid is flowing horizontally from a region of high pressure to a region of low pressure, then there is more pressure behind than in front. This gives a net force on the volume, accelerating it along the streamline.