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Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 21 Apr 2021, 13:48
by lynch
I suppose you have something like a 4 core i7 with 16Gb like me.
Let's see how it will run.
As soon as the rules are published I will for the first time engage in something like this.
CFD I have experience as it's part of my daily job car design it's something new.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 02:22
by spacehead3
Hi all,
I posted some results and images of the 2021 Williams car on my blog, figured you all might be interested:
https://maxtayloraero.wordpress.com/202 ... ms-f1-cfd/
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 17:06
by variante
Thanks!
Those floor vortices are impressive!
For those who are interested, these are the results of the Williams tested in MVRC settings (but with no internal aero):
CDA = 1.55
CLA = 3.23
CoP = 2.13
PS: 1 degree of rake; rough strakes present; rear suspensions moved to match non-standard rake.
PPS: MVRC ride height; wooden plank added.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 17:36
by LVDH
Very interesting to see the comparison of the numbers.
How did you run it Max?
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 18:25
by spacehead3
LVDH wrote: ↑22 Apr 2021, 17:36
Very interesting to see the comparison of the numbers.
How did you run it Max?
For reference here my numbers are CL=-4.598, CD=1.746
Variante and I chatted a bit about this last week, and I think we have 2 major differences:
1) I used 2 deg rake and he used 1 deg. If I drop my car to 1 deg rake, I get CL=-3.991, CD=1.640.
2) I put the entire body in the high-res folder, he used the normal MVRC mesh assignments. If I move the body out of high-res, I get CL=-4.028, CD=1.750
So adding those 2 changes together brings my numbers down to roughly CL=-3.421, CD=1.644, which is pretty close to what Variante got.
Essentially half of the difference is from rake, and the other half is from the mesh quality. When you look at the vortices along the floor you can understand why having the floor in high-res made such a big difference. Here is the normal floor (left) vs the high-res floor (right)
https://drive.google.com/file/d/1J5B7kK ... sp=sharing
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 19:56
by hollus
Is that a vortex from the cape going directly under the floor in that Williams model? 2 degree rake, I assume?
By the way, let me know is splitting the Williams' discussion to a new thread would be a good idea. I think it is OK here, though?
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 19:59
by jjn9128
Where'd you get the 2 degrees rake? Seems extreme, even for modern F1. I think max is ~1.8, it's been a while since I've seen amus publish a guess of F1 ride heights though.
F1 teams will tend to note front and rear ride heights though. 1 deg of rake is a 63mm difference in ride height front-to-rear, I measured the wheelbase at ~3603mm, 2deg is a 126mm difference.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 20:01
by jjn9128
hollus wrote: ↑22 Apr 2021, 19:56
Is that a vortex from the cape going directly under the floor in that Williams model? 2 degree rake, I assume?
By the way, let me know is splitting the Williams' discussion to a new thread would be a good idea. I think it is OK here, though?
Looks like.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 20:20
by spacehead3
jjn9128 wrote: ↑22 Apr 2021, 19:59
Where'd you get the 2 degrees rake? Seems extreme, even for modern F1. I think max is ~1.8, it's been a while since I've seen amus publish a guess of F1 ride heights though.
That is how the spindle positions were set up in the model, 2.08 degrees to be exact. A quick google found some estimates for the 2018 redbull at 1.9 degrees, and that was at speed. I assume this 2.08 would be the static attitude, so that seems to line up well.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 20:24
by jjn9128
spacehead3 wrote: ↑22 Apr 2021, 20:20
That is how the spindle positions were set up in the model, 2.08 degrees to be exact. A quick google found some estimates for the 2018 redbull at 1.9 degrees, and that was at speed. I assume this 2.08 would be the static attitude, so that seems to line up well.
Aaaaah, okay. Good point.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 22 Apr 2021, 20:50
by LVDH
spacehead3 wrote: ↑22 Apr 2021, 18:25
LVDH wrote: ↑22 Apr 2021, 17:36
Very interesting to see the comparison of the numbers.
How did you run it Max?
For reference here my numbers are CL=-4.598, CD=1.746
Variante and I chatted a bit about this last week, and I think we have 2 major differences:
1) I used 2 deg rake and he used 1 deg. If I drop my car to 1 deg rake, I get CL=-3.991, CD=1.640.
2) I put the entire body in the high-res folder, he used the normal MVRC mesh assignments. If I move the body out of high-res, I get CL=-4.028, CD=1.750
So adding those 2 changes together brings my numbers down to roughly CL=-3.421, CD=1.644, which is pretty close to what Variante got.
Essentially half of the difference is from rake, and the other half is from the mesh quality. When you look at the vortices along the floor you can understand why having the floor in high-res made such a big difference. Here is the normal floor (left) vs the high-res floor (right)
https://drive.google.com/file/d/1J5B7kK ... sp=sharing
It is very interesting to see the numbers out of your experiments. I am not so happy that the mesh resolution change caused such a difference. Did you try to run the front and rear wings only as high res parts?
The next version you guys will be getting of MFlow will not require any such hacks anymore to run different cars! You will be able to run whatever you want!
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 08 Jun 2021, 08:46
by Joe7218
Any update on this year's comp?
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 12 Jun 2021, 15:04
by Stu
jjn9128 wrote: ↑13 Apr 2021, 15:20
LegendaryM wrote: ↑13 Apr 2021, 13:55
I found this very helpful script for Onshape:
https://forum.onshape.com/discussion/95 ... ure-script which makes a nice aerofoil from a chord line and a few parameters, with I think a TE thickness of 2mm. It's very similar to what's used in industry and I'm quite happy I found it because drawing aerofoils is quite a tedious process.
Not far off how I define aerofoils. Essentially an ellipsis and a pair of splines (a spline where you can control magnitude of the handles is preferable to giving a dimension but OnShape doesn't have that option within a sketch). Designing wings is one of my favourite things
https://db3pap006files.storage.live.com ... pmode=none
I’m very late getting back to this thread, but do you have a method of calculating (estimating!) lift:drag forces purely from the 3D version (2D x span) without running it through CFD? I’m curious, as you could then design a profile purely for the aero load that you wish to generate.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 12 Jun 2021, 19:08
by CAEdevice
Stu wrote: ↑12 Jun 2021, 15:04
jjn9128 wrote: ↑13 Apr 2021, 15:20
LegendaryM wrote: ↑13 Apr 2021, 13:55
I found this very helpful script for Onshape:
https://forum.onshape.com/discussion/95 ... ure-script which makes a nice aerofoil from a chord line and a few parameters, with I think a TE thickness of 2mm. It's very similar to what's used in industry and I'm quite happy I found it because drawing aerofoils is quite a tedious process.
Not far off how I define aerofoils. Essentially an ellipsis and a pair of splines (a spline where you can control magnitude of the handles is preferable to giving a dimension but OnShape doesn't have that option within a sketch). Designing wings is one of my favourite things
https://db3pap006files.storage.live.com ... pmode=none
I’m very late getting back to this thread, but do you have a method of calculating (estimating!) lift:drag forces purely from the 3D version (2D x span) without running it through CFD? I’m curious, as you could then design a profile purely for the aero load that you wish to generate.
No I never tried to estimate lift analytically, even if some parts of the car are almost extruded 2D profiles (i.e.rear wing, diffuser for some cars) the flow is remarkably 3D.
Re: [MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)
Posted: 12 Jun 2021, 19:35
by spacehead3
Could try xfoil / XFLR5, but like CAE says it may not be too applicable to what's happening on your car.