[KVRC] Khamsin Virtual Racecar Challenge 2016

[CAEdevice]

Next year we could split thermal engine and kers cooling devices/ducts (2+1 heat exchangers), just to add some new design variables (next year, beacuse we made Julien work too hard this time).

[julien.decharentenay]

Yeah, I am afraid I have been stretching too far this time around - but it is getting together (slowly)... The last couple of seasons were easier on me.

New patch for OCCFD can be downloaded at http://www.khamsinvirtualracecarchallen ... .1-002.zip with essentially the following fixes:

- Part names are handled correctly for v2.3 and above - openFoam from cfd support should now work fine;
- Altered the calculation of normals to have a faster turn-around (thanks Matteo);
- Amazon AWS should work (once the AMI is public which is should be by the time you read it);
- The post-processing should be back in place.

OCCFD v1,1.002 handles the porous radiators, but the coefficients are not finalised. I have to run some more testing to ensure I get a consistent behavior: essentially based on getting the right flow rate/pressure drop combination for the 100mm thickness. It will be v1.1.003 - and I am expecting something for this weekend.

Any bug or issue, please send me an email at julien@khamsinvirtualracecarchallenge.com rather than PM me.

[julien.decharentenay]

And let me know if it works as well...

[julien.decharentenay]

Great.... I used an ubuntu instance from the Amazon Marketplace as a starting point. Now when I want to make the AMI public I receive the following error message:

Code: Select all

Modifying permissions failed for the following resources: ami-962b14fc. Images with marketplace product codes may not be made public. (Service: AmazonEC2; Status Code: 400; Error Code: OperationNotPermitted; Request ID: 3d734581-6d64-4dbe-9a67-48f64fab488b)

Painful... If you are planning to use Amazon with OCCFD v1.1.002 and above, please send me an email with an AWS account number so that I can add your details to the Amazon AMI.... Until I sort this out with rebuilding an AMI from scratch (again)...

[LVDH]

Will there be a Linux version to run locally?

[CAEdevice]

Hi Julien, I think I'll try it tomorrow in the morning, I noticed your message only now, I'm sorry!

[cdsavage]

A (nearly) final version of the rulebook is available here: http://www.khamsinvirtualracecarchallen ... nge-2016-1

The only thing open for change is the method used for K4.1 option 2 (the submission of the heat exchanger parts will be slightly different depending on which way we go). The intent is to use a porosity for the heat exchanger volume, and then measure the flow rate. Julien is working very hard on this, but in case it's not ready in time, the fallback method is also shown.

Other than that, and possibly some minor adjustments to the figures in appendix 2, this will be the definitive rulebook.

[CAEdevice]

Just a curiosity about the tracks: from the appendix it looks that Silverstone is more a "downforce" than an "efficiency" track. Is this right?

[machin]

Silverstone rewards both high downforce and low drag... So it's sort of a half way house... But yes; nearer to high downforce...

You can try it out on the test track: all tracks available to all participants;

http://competition-car-engineering.com/VSW_KVtest.htm

[CAEdevice]

Thanks machin I guess that efficiency will be more important at Silverstone than Nurburgring... is it correct?

[machin]

The characteristics of Silverstone might be surprising at first, but it has some really high speed sweeping bends which reward high downforce, and it doesn't really have any really long straights, although it does have quite a few medium length ones. The Nurburgring has lots of tight corners and short straights but it does have one huge long straight... This means that they're not too far away from eachother in terms of aerodynamic trade-off.

One thing to note: Every track will be run with 540bhp in 2016 (assuming you get your cooling and intake/exhaust flows sorted OK!)... whereas last year the Nurburgring and Monaco were run with 600bhp... this means that there is a slight increase in importance of efficiency at Nurburgring (not really at Monaco).

However; the determination of the best set-up really comes down to a case-by-case analysis; if your car has lots of drag then Virtual Stopwatch will tell you that you will gain most by reducing drag. If you already have really low drag then Virtual Stopwatch will tell you to concentrate on downforce production, therefore I would be inclined to follow the following sort of procedure:

• Determine from your past results/designs three sets of aero coefficients representing high/medium/low downforce configurations. If you're new to the champsionship look back on the results from last year and pick 3 competitors cars which have high/medium/low downforce configurations.
• Input the three configurations into Virtual Stopwatch and see what the results are at the track you're interested in. Pick the fastest one.
• For the fastest one now look at the data display at the bottom of the Virtual Stopwatch page. There you wil find the effect on lap time of 20% increases in downforce (no change to drag) and 20% decrease in drag (no change to downforce). Both those changes will make you faster regardless of track, but the key is finding out which one gives you the biggest gains.
• Once you know that you can interrogate the CFD analysis of your car and figure out where to make the downforce gains or drag reductions needed to improve your lap time.

[CAEdevice]

Thanks Machin! The increase of the importance of efficiency is good in my point of view.

[LVDH]

Are you sure?
Wasn't your car usually the one with one of the highest drag values?

[CAEdevice]

Are you sure?
Wasn't your car usually the one with one of the highest drag values?

Yes, you are right. But I wrote "in my opinion", not "in my interest"
I think that designing a car (expecially LMPx shaped) without considering efficiency is quite boring, even if my car concept is stronger in high df tracks.

[Markus]

Could someone verify that the latest parts file for Sketchup is correct? The one I get downloaded seems really weird.