Khamsin Virtual Racecar Challenge 2014

[astracrazy]

it does yes, as in real life they wouldn't (in extreme case) put it behind the drivers head. In the same extreme case it would be a drag advantage to do this (in this competition)

I run a test with them and noticed no real difference, in fact with the winglets on the rear you should be able to get more downforce

[cdsavage]

Any news yet on what mesh settings will be used?

[astracrazy]

Not yet sorry ill hopefully have news shortly

We should hopefully have some news regarding cfd in the next few days

[variante]

in fact with the winglets on the rear you should be able to get more downforce

unfortunately those winglets create a low pressure field on top of the car's floor...
Also, the rear tires look more "squared" so they seem to create a greated inwash, which disrupts diffuser's airflow.
Luckily aero-balance resulted almost unchanged because of the negative action of the lowered front suspensions and of a more intrusive turning vane.

Please, notice that i'm not complaining: i just want to know wheter my CFD results of the new suspensions complex are reliable or not.

[astracrazy]

no its fine, more feedback the better

I checked and got the same balance but didn't look beyond that. cd has spoken to me about some flow separation and wanted to bring an update but I was reluctant because I was unsure about how people would feel about it (in relation to designing there cars)

[cdsavage]

Honestly its not that important since its the same part for everybody. I think its more important to have the mesh settings/test cases locked in, and at this point just commit to the spec parts we have now.

BTW the wheels are pretty much identical in shape to the 2013 wheels apart from having more polygons, plus the front wheels have some camber.

[astracrazy]

I tend to agree. We now have 14 pre-registered teams so I don't want to change spec parts because maybe its working for somebody else depending on there design around the part. Maybe not. But you get my point.

Regarding cfd/mesh. Sorry for the delay. Julien is away this week on holiday (which is why we aimed for the 5th) but its taking longer than expected. He is working on 2 things:

1) the mesh but is related to a different way he is trying to do it. its sort of 2 steps forward 1 back. I think the goal is better results for less

2) he is working on a portal for the website which will have two functions (hopefully). like last year, where you can upload your designs for the races. And also the option to get your model converted to a openfoam cfd case set up so you can test your cars yourself between races. I'm not sure on the works of it yet, or if you'll need to download other programs. At a guess i'd say you'd need paraview.

I'm a bit vague with number 2 as its more Juliens field.

[variante]

I agree as well.

But, cdsavage, did you test your wheels/suspensions in comparison to the old ones or not? I did it with what i consider "accurate testing conditions" and obtained a 18% loss in downforce (caused by what i described earlier) despite the results being stable. Now, 18% is a lot so i wonder where i failed...unless its a normal result.
I'll run other tests to confirm the accuracy of the previous ones, obviously.

[cdsavage]

I didn't do a back to back with the new wheels. One consideration is that with a higher polygon count the surface of the wheel is smoother which might change the separation point on the wheel. The front suspension is also a good bit lower due to the lower tub, which might have an effect on the FW.

About the mesh - last year a .skp was provided for each case with everything already set up for a simulation, all that we needed to do was import the car and place it in the correct group. I thought that worked fine.

[astracrazy]

cdsavage - Oh yes i agree it worked fine. What i will do is get Julien to do the same this year.
But for new comers and to make it easier/more accessible this way can easier. I'm guessing the need to download and set up Khamsin etc won't be needed but i need to confirm.

---

Again sorry for the delay with the mesh settings and cost. I know Julien is cracking on.

[RicME85]

I guess what Julien is planning on doing is similar to the portal that he created for quick, accessible CFD - Aerodynamic on Demand

Oddly have no interest in this at the moment
Have opened up my 2014 .skp several times, start drawing a tub then closed it. will see if the impending car launches spark any enthusiasm.

[astracrazy]

i think you've hit the nail on the head. which is prob going to be a lot easier for newcomers

[CottrellGP]

Hi guys, not sure if it has been mentioned before but last year i struggled getting and CFD work done on my car because simply i didn't know how do fully install Khamsin and i struggled using it. Maybe there could be some simple instructions could be uploaded somewhere. I know there was a YouTube video of how to set it up but even that is complicated. Thanks

[astracrazy]

I will get Julien to do some instructions soon. But, as above, this portal should help you....

[CAEdevice]

Hi, I'm trying to model a test shape to comply with the rules.

I have a doubt related to CFD simulation of the inlet/outlet: it would be possibile to know more about BC defined on these surfaces?