2017 front wings downforce compared to 2010

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Dipesh1995
9
Joined: Mon Apr 21, 2014 4:11 pm

Re: 2017 front wings downforce compared to 2010

Post by Dipesh1995 » Sat Aug 12, 2017 9:54 pm

jjn9128 wrote:
Sat Aug 12, 2017 7:45 pm
Dipesh1995 wrote:
Sat Aug 12, 2017 6:51 pm
Ok so I'll first run the wing in isolation to make sure there's no fundamental issues with it after which I'll run it with a rotating wheel in a set up identical to what Pegrum used. One question I have is that a rotating wheel is fundamentally an unsteady problem however would I be able to get away with running with a steady solver like CD-adapco have done for their FSAE car even though they're running with rotating wheels?
@ 6.00 mins approx and 10.55 mins : https://www.youtube.com/watch?v=f1UL4o9rdJs

If not, would a implicit solver be better than a explicit solver for this problem? I'm leaning towards implicit as I can run with larger time steps and tends to be more stable.
I would say a steady solver is fine, Vyssion may disagree. To run a properly transient case would need to run without a symmetry plane, doubling your cell count. My philosophy with CFD (certainly at university level) is to run what your machine is capable of running, if your cell count isn't as high as you'd like or your solver is a compromise, if you can critically explain the results then thats fine. Ultimately CFD is just a simulation, there are studies from Chinese facilities running tens of billions of cells and the accuracy (to a wind tunnel simulation) was not really any better, drag was better predicted but lift was worse or whatever.
Yeah I agree, running steady won’t give the most accurate answer but it should give a good indication of the wing’s performance.

Vyssion
52
User avatar
Joined: Sun Jun 10, 2012 1:40 pm

Re: 2017 front wings downforce compared to 2010

Post by Vyssion » Mon Aug 14, 2017 6:01 pm

jjn9128 wrote:
Sat Aug 12, 2017 10:58 am
Dipesh1995 wrote:
Fri Aug 11, 2017 6:55 pm
Nope not yet. I'll hopefully be able to do that after I do the ride height sensitivity study. At the moment, I'm just working on getting spec 2.1 ready. Like I said, I reckon there's still more performance to unlock with this wing.
You may find yourself unlocking that performance in isolation then losing it with the presence of the wheel. The wing and wheel have opposite circulation, so the wheel will work to cancel the circulation of the wing and vice versa, considering your wings span this will be especially prevalent towards the edge vortex you're working so hard to develop. This is also very true with a ride height study, different ride heights will change the way the wing/wheel system interacts, with positive or negative results. Likewise the gap between the trailing edge of your wing and the front point of your tyre - in F1 this is fixed by the legality boxes not optimal performance.

Check out theses and papers from Pegrum, van den Berg, Heyder-Bruckner, Diasinos, and Kellar to see how the wing cannot be considered without a wheel. I know Pegrum is now very senior at McLaren, Diasinos worked for Toyota when they were in F1, and the Kellar paper included Pearse who I think is now head of aero performance at Mercedes so they're top sources. I would also try to use a more representative tyre profile, check out Sprot's SAE paper which has scans with coordinates of the contact patch and upper deformation of a F1 tyre on a 13" rim.
^ This... For pretty much the same reason that jjn9128 suggested you extend your nose cone much further downstream. The shear "presence" of the wheel will affect the aerodynamics both downstream AND upstream (perhaps not all that much for a little winglet or something, but definitely a fair bit for a wheel; which is THE biggest annoyance of mine to mesh and simulate) :?


jjn9128 wrote:
Sat Aug 12, 2017 7:45 pm
I would say a steady solver is fine, Vyssion may disagree. To run a properly transient case would need to run without a symmetry plane, doubling your cell count. My philosophy with CFD (certainly at university level) is to run what your machine is capable of running, if your cell count isn't as high as you'd like or your solver is a compromise, if you can critically explain the results then thats fine. Ultimately CFD is just a simulation, there are studies from Chinese facilities running tens of billions of cells and the accuracy (to a wind tunnel simulation) was not really any better, drag was better predicted but lift was worse or whatever.
Nah, agree - at least for this level of simulation we are going for; KISS = Keep It Simple Stupid :lol:
If you can't explain it simply, then you don't understand it well enough.
The great thing about facts is that they are true, whether or not you believe them. - Neil deGrasse Tyson
Vyssion Scribd - Aerodynamics Papers

Dipesh1995
9
Joined: Mon Apr 21, 2014 4:11 pm

Re: 2017 front wings downforce compared to 2010

Post by Dipesh1995 » Tue Aug 15, 2017 11:50 am

Ok so I'll run a mesh sensitivity study for the rotating wheel in isolation once I get round to it before combining it with wing and nose setup; atm, I'm just working on spec 2.1.

Dipesh1995
9
Joined: Mon Apr 21, 2014 4:11 pm

Re: 2017 front wings downforce compared to 2010

Post by Dipesh1995 » Wed Aug 16, 2017 7:25 pm

So I've done a mesh sensitivity study for a rotating wheel. Dimensions of the wheel are 630mm diameter and 289 mm width, and the radius on the edges of the wheel is 31.5mm. It is sunk into the ground plane by 20mm. It is therefore a bit smaller than a F1 tyre but the car is designed around those wheel dimensions so I'm not going to change them.

https://goo.gl/photos/8BMqeLA49XvwZygt8

I've included mesh scenes (Y+ is between 25 and 75 for nearly all of the wheel), a contour plot showing the flow around the wheel (trailing region of the wheel looks like an angry octopus :lol: ), isosurface plots with Q criterion (10000 /s^2) which show the two vortices forming from the edges of the wheel, and a vector plot showing showing the wake of the wheel (20 cm from the wheel).

Drag of the wheel 222 N and lift is 227 N.

Hopefully, I'll be able to put the wing and wheel together later on this week or next week which will show the true colours of the wing to a large enough extent.



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