Khamsin Virtual Racecar challenge 2013 (CFD model racing)

[variante]

Totally agree, Cottrell.
It's just that, after a good amount of time working on the car, i am tasting that slight bitter flavor because of how things have gone...
Anyway, I share your feelings about Nick and Julien.

[CottrellGP]

Totally agree, Cottrell.
It's just that, after a good amount of time working on the car, i am tasting that slight bitter flavor because of how things have gone...
Anyway, I share your feelings about Nick and Julien.

I totally agree with you, I haveve worked mega mega hard months and months and if mine was illegal i would be pretty upset too!

[julien.decharentenay]

Hi,

Thanks a lot for the feedback. I agree with your comments and understand the frustration. From my side, I say "bravo" to the hard work of all the teams as there is a lot of thoughts and hardwork put in the designs.

From my perspective, I think that the competition is better if none of the car are deemed "illegal". I am thinking that a two-step submission: (1) submission for compliance and (2) re-submission for the race would be better as it means that there is an window of opportunity to correct minor compliance issues (how long would be enough?). Or should we provide a design compliance submission independent from the race [it would keep Nick busy] or just at the start of the season?

Any suggestion welcome.

Renders are shown in the following gallery: https://plus.google.com/photos/11084579 ... 0496161985 - it would be great for future if a "copyright (C) team XYZ" notice can be added somewhere on the picture and a reference to Khamsin Virtual Racecar Challenge as well.

[cdsavage]

Any suggestion welcome.

One thing that has been a problem for me is the requirement to submit the car as a native sketchup file - it is a real pain importing a model from a cad package, using different formats for different parts of the car so that the imported model isnt too coarse and faceted, but at the same time keeping under a 50mb filesize. All the STP or IGES importers for sketchup seem to import a really coarse model that would impact the CFD results, but using STL for the whole car isnt possible because the filesize would be huge. If it was possible to use some NURBS format natively without going through sketchup the model would be perfectly accurate and the filesize would be less than 10mb. Even if I could just use STL without having to actually import it into sketchup would be a big improvement.

[machin]

I thought I would add some colour to this thread (literally!):-

Variante:- (Cl.A-Front =-1.18, Cl.A-Rear=-1.73)


JJR:- (Cl.A-Front =-1.11, Cl.A-Rear = -1.83)


CSR:- (Cl.A-Front =-1.07, Cl.A-Rear = -1.77)


All the other cars can be seen by going to the Khamsin Challenge website and clicking on the image at the bottom of this page:-

http://www.khamsinvirtualracecarchallen ... -french-gp

[N12ck]

Hi,

With regards to regulations, before the season started I said what would be clamped down on and these have. It is impossible to check most regulations on 12 cars within a week, so we focus on a select number of regulations, doing this we obviously create discussion. However the list for what we check was emailed a few months/weeks ago.

(The wrong sized wings or wings which were in the wrong place were penalised)

With regards to what Julien says, I see the way forward being an idea like this:

Here's a cockpit, here's a gearbox/engine, certain intake/outlet areas, make the car within these boxes, anything goes, that's an idea, what do you think?
Thanks
Nick

[astracrazy]

I fail to understand how (no disrespect) Blinblom's car can be legal with those sidepods?


for 2014, i think that may be a better idea Nick. Use the F1 reg boxes but allow more freedom within them. But i would say there needs to be some restrictions added, in some way, around the side pod area.

[Markus]

I fail to understand how (no disrespect) Blinblom's car can be legal with those sidepods?
https://lh6.googleusercontent.com/-SUPJ ... 180mph.png

for 2014, i think that may be a better idea Nick. Use the F1 reg boxes but allow more freedom within them. But i would say there needs to be some restrictions added, in some way, around the side pod area.

Thanks for the opinion Astra. I definitively understand what you mean by the sidepods.
I'm definitely going to fix that for the next and it may even make my car a bit faster.
But as you guys have said I think we need a specified regulation for the measurements around the sidepods.

[variante]

I fail to understand how (no disrespect) Blinblom's car can be legal with those sidepods?

...and this is not the only case: i've been able to spot illegal elements (some bigger, some smaller) on every single car, and i did it just by looking at the published photos (this is why i was complaining about my penalty).

About next season: i'd suggest simply to improve the supplied tub so it shows where to do what ("in this box you can build anything with a radius>75mm", etc). Of course it's really hard to follow every single rule of the F1...we would need a lawyer... So i propose to go on using F1 official regs ('cause they make the challenge a lot more interesting, IMO) with tolerance for minor rule infringiments.

[astracrazy]

i would suggest using the f1 reg boxes but then creating own rules within those boxes (like they have down with the inlets/colling etc)
.
1) it will be easier for competitors to follow
2) everyone will be fully clear on what is legal and not
3) it will be easier for nick etc to test for legality

that way we can all build within the boxes but to the rules nick etc supply. So like you say, in the sidepod area they could we say minimum radius 75 mm and minimum volume must be no less than x (just an example)

more open than the f1 rules (within the reg boxes) but still some rules to make it not a free for all. to follow the whole f1 rules is too much in this competition (for everyone).

[julien.decharentenay]

Hi. Thanks for the suggestion. Just submit the STL in place of SketchUp file through the submission portal [binary file should be fine, ignore the text saying submit a SketchUp file]. If I have an issue with the file, I will contact you directly.

Unfortunately, I can't do NURBS at this stage - not STEP or IGES....

Any suggestion welcome.

One thing that has been a problem for me is the requirement to submit the car as a native sketchup file - it is a real pain importing a model from a cad package, using different formats for different parts of the car so that the imported model isnt too coarse and faceted, but at the same time keeping under a 50mb filesize. All the STP or IGES importers for sketchup seem to import a really coarse model that would impact the CFD results, but using STL for the whole car isnt possible because the filesize would be huge. If it was possible to use some NURBS format natively without going through sketchup the model would be perfectly accurate and the filesize would be less than 10mb. Even if I could just use STL without having to actually import it into sketchup would be a big improvement.

[cdsavage]

Thanks Julien, that makes things easier for me.

I have a potentially dumb question: does the downforce distribution front/rear take into account the moment due to the drag force? I'm trying to work out why there is such a discrepancy in f/r balance between the KVRC results and my own tests.

[julien.decharentenay]

In the test race that was run at the end of last year, it did not. In the Magny-Cours race, the moment due to drag is taken into account to calculate the balance front/rear. My geometry is quite poor - it took me a lot of head banging to realise that force and moment are not sufficient to establish the COP. I applied that the COP was at ground level as the downforce is applied at the point of contact between wheels and road.

I would be more than happy to discuss/refine the approach. The mesh and turbulence model may also have an impact along with the use of STL in place of NURBS (in the former curves are split into segments - this is the reason of the non-smooth color of pressure on the wheels in the pictures shown above).

Thanks Julien, that makes things easier for me.

I have a potentially dumb question: does the downforce distribution front/rear take into account the moment due to the drag force? I'm trying to work out why there is such a discrepancy in f/r balance between the KVRC results and my own tests.

[RicME85]

real shame at the distinct lack of cars submitted once again

[machin]

How many were there this time?

Last time we had 12 teams, which is more than the current number of teams in F1!