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Old 05-20-2013, 02:38 AM   #141
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Quote:
Originally Posted by mx5-kiwi View Post
One other key point, my car has a front air dam that is angled up for kerbs/clearance etc. Somewhere (this thread?) I asked if you could run a splitter even if the angle was not flat....it would appear Mclaren think you can....
You see the edge of it, underneath it would most probably have diffusors etc.
I.e. it's most probably not just a flat plane with that angle.
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Old 05-20-2013, 12:14 PM   #142
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It might just be the angle that picture is taken from making it look like the splitter isn't horizontal to the ground.

As for those canards on the mclaren, it looks like those are partially designed to serve as tire spats, which might account for the steep angle if they wanted to cover the front area of the tire.

-Ryan
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Old 05-20-2013, 03:51 PM   #143
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No, they don't appear to be there to cover the tire, as the other elements of the nose are completely covering the tire.

I'm going to make a WAG here and say there's no way we can really determine what the specific function of these canards on this car is without CFD results.



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Old 05-20-2013, 11:08 PM   #144
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Perhaps they are multi element to further help the formation of vortices down the side of the car (remember, f1 uses slots as vortex generators on their underbodies).
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Old 05-21-2013, 12:38 AM   #145
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Quote:
Originally Posted by mx5-kiwi View Post
I thought canards are to disrupt airflow down the side of the car (by reducing airflow entering underneath from the side) that being the case maybe the small gaps help create more/multiple disruptive vortice's than just the single trailing edge of a one piece?
Yes they act as vortex generators to do many things

Quote:
Originally Posted by mx5-kiwi View Post
Multi plane wing is for aerodynamic efficiency I wouldn't have thought an efficient down force generator there is the idea...unless it / canards do both?
Multiple element wings are very inefficient. They are for max downforce


Quote:
Originally Posted by mx5-kiwi View Post
One other key point, my car has a front air dam that is angled up for kerbs/clearance etc. Somewhere (this thread?) I asked if you could run a splitter even if the angle was not flat....it would appear Mclaren think you can....
You do not want to run the splitter at an angle, especially up unless you want to create lift.
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Old 05-21-2013, 12:38 AM   #146
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Quote:
Originally Posted by motormechanic View Post
Perhaps they are multi element to further help the formation of vortices down the side of the car (remember, f1 uses slots as vortex generators on their underbodies).
This
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Old 05-21-2013, 01:45 AM   #147
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Quote:
Originally Posted by plucas View Post
Multiple element wings are very inefficient. They are for max downforce
I'm not sure what you mean. I went with a multi element wing because the theoretical single element wing to make the amount of downforce mine theoretically makes would be bigger than the rules allow and have 4 times as much drag.
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Old 05-21-2013, 02:59 AM   #148
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Quote:
You do not want to run the splitter at an angle, especially up unless you want to create lift
I dont want to be argumentative because I cetainly have no experience to back this up but...this statement seems very hard to comprehend. I would think many performance road cars have up angled splitters in order to retain some form of obstruction clearance (minimal though that may be...)

Also due to the fact that the McLaren photos shown above has the front edge of the splitter on an angle/raised higher at the front. I would say by about 2 cm/1 inch.....


Quote:
You see the edge of it, underneath it would most probably have diffusors etc. I.e. it's most probably not just a flat plane with that angle.
- Reading Niklasfalk's comment, quite possible but that would then mean you can run an angled spitter so long as you have some form of diffuser underneath....however it does appear to be flat.
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Old 05-21-2013, 03:14 AM   #149
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I believe the photo is deceiving. We don't have a good horizontal reference. The suspension is at full droop. I can't find a good side shot of the GT3 on the ground. But the splitter looks to be horizontal to me.

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Old 05-21-2013, 10:14 AM   #150
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Fine i'll play, Cover them in front, open them in back.

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Old 05-21-2013, 01:30 PM   #151
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Quote:
Originally Posted by Leafy View Post
I'm not sure what you mean. I went with a multi element wing because the theoretical single element wing to make the amount of downforce mine theoretically makes would be bigger than the rules allow and have 4 times as much drag.
Where did you get the info and can you post it?

Multiple element wings have a greater induced drag than a single element wings. Multiple elements are used when single elements do not make the downforce required.
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Old 05-21-2013, 02:00 PM   #152
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I'll have to try and find the study. My main computer just got a massive upgrade (yay 4 times as much ram and better processor) and HD wipe (now I have room for a linux partition for open FOAM) so my CFD studies are hiding somewhere on my backups. The issue was trying to hit my 450 lbs @ 60mph goal required a pretty stupid, massive, huge AOA, tons of camber single element, where as the dual element was able to straight up more efficiently use the air, less flow separation and that jazz.
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Old 05-21-2013, 03:22 PM   #153
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Old 05-21-2013, 03:35 PM   #154
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Quote:
Originally Posted by Leafy View Post
I'll have to try and find the study. My main computer just got a massive upgrade (yay 4 times as much ram and better processor) and HD wipe (now I have room for a linux partition for open FOAM) so my CFD studies are hiding somewhere on my backups. The issue was trying to hit my 450 lbs @ 60mph goal required a pretty stupid, massive, huge AOA, tons of camber single element, where as the dual element was able to straight up more efficiently use the air, less flow separation and that jazz.
But that is comparing apples and oranges. You are comparing the efficiency of a stalled single element to a non-stalled multi-element wing. When the wing stalls, the drag shoots up and lift/downforce decreases. So of course it will be more efficient. You went multi-element wing since you needed more downforce which is what I said earlier

Also what turbulence model and wall functions are you using in OpenFoam? Depending on that, the numbers can be wrong.
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Old 05-21-2013, 03:48 PM   #155
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Quote:
Originally Posted by plucas View Post
But that is comparing apples and oranges. You are comparing the efficiency of a stalled single element to a non-stalled multi-element wing. When the wing stalls, the drag shoots up and lift/downforce decreases. So of course it will be more efficient. You went multi-element wing since you needed more downforce which is what I said earlier

Also what turbulence model and wall functions are you using in OpenFoam? Depending on that, the numbers can be wrong.
Used COSMOS for that stuff. Haven't had a computer besides my netbook with linux so I haven't used open FOAM yet. I did have some problems getting COSMOS to react as expected at first until I realized I had my goals set wrong. I'm also not going to claim my wing makes 450 lbs @ 60mph, the model says it does but it was analyzed off the car, and I dont really trust COSMOS to be that accurate. It certainly does make some downforce in real life, but its unmeasured.
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Old 05-21-2013, 06:00 PM   #156
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Quote:
Originally Posted by mx5-kiwi View Post
I dont want to be argumentative because I cetainly have no experience to back this up but...this statement seems very hard to comprehend. I would think many performance road cars have up angled splitters in order to retain some form of obstruction clearance (minimal though that may be...)

Also due to the fact that the McLaren photos shown above has the front edge of the splitter on an angle/raised higher at the front. I would say by about 2 cm/1 inch.....

- Reading Niklasfalk's comment, quite possible but that would then mean you can run an angled spitter so long as you have some form of diffuser underneath....however it does appear to be flat.
I think that is just the picture as it appears flat in other pictures. I still stand by that you do not want to angle you splitter, especially up. Having it angled up will cause more lift than if horizontal to the ground.

Quote:
Originally Posted by Leafy View Post
Used COSMOS for that stuff. Haven't had a computer besides my netbook with linux so I haven't used open FOAM yet. I did have some problems getting COSMOS to react as expected at first until I realized I had my goals set wrong. I'm also not going to claim my wing makes 450 lbs @ 60mph, the model says it does but it was analyzed off the car, and I dont really trust COSMOS to be that accurate. It certainly does make some downforce in real life, but its unmeasured.
Good luck learning OpenFOAM. It is a big task for sure. It took me a good while to figure it all out and I came from using fluent. My biggest issue was learning how to set boundary conditions and getting a quality mesh (still use shm).
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Old 05-21-2013, 08:45 PM   #157
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Quote:
Originally Posted by motormechanic View Post
Perhaps they are multi element to further help the formation of vortices down the side of the car (remember, f1 uses slots as vortex generators on their underbodies).
Perhaps those vortices help feed the intake for the engine.

I'm not a fan of the aesthetics of the dive planes mounted on top of the vertical elements...too much going on.
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Old 05-22-2013, 01:52 AM   #158
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Having the splitter turning up at the leading edge is good if you have a flat floor and rear diffuser. You need to feed the air to the underbody. If no flat floor. I would block as much air going under as possible.
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Old 05-22-2013, 12:41 PM   #159
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A raised center section for the splitter would be better than the leading edge just rounding upwards I would think.

I am with plucas, I think that at least in 99.9% of applications, unless there's some other strange elements going on that make some sort of use of it, you don't want a splitter angled up in front. Especially since the splitter's purpose is to provide downforce, which is does well when horizontal, and even better when angled very slightly down in the front (splitter bottom surface can act as a diffuser)

-Ryan
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Old 05-22-2013, 01:33 PM   #160
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Wouldn't a raised leading edge (to a degree) enhance the venturi shape (which is the basis of how downforce is made through the ground effect) more than it creates lift?

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