Khamsin Virtual Racecar Challenge 2015

[JJR]

It looks like that some of you are thinking about removing rear wing in next rounds.
I think that in middle / low downforce configuration is rear wing verry efficient ( l/d ratio 10 + ) and one of most efficient part of car. So from my point of view it is better to use it.
I agree with Mantium Ray that in next round we are going to see cars with better l/d ratio than in high downforce config.

Cool car Matteo ( Panoz like ) with impressive aero figures for not fully developed machine !

[sjns]

Congratulations to the winning teams! =D> =D>

Looking forward to the next race and all the "new" cars. I hope I'll find enough time to properly work on my car in the next days. Otherwise it probably will be a shot in the dark.

[CAEdevice]

I was wondering how the next tracks could be defined: medium df? low df? efficiency tracks? Last year Magny Cours (that I considered a medium/low df circuit) has been an *extreme low* df track (it was possible to reach the podium running almost without wings).

Is the test track ideal setup near to each of the next three race setup?

[cdsavage]

I was wondering how the next tracks could be defined: medium df? low df? efficiency tracks? Last year Magny Cours (that I considered a medium/low df circuit) has been an *extreme low* df track (it was possible to reach the podium running almost without wings).

The setup requirements for these rounds are very similar. I would describe them as medium to low downforce, but it will depend on the efficiency that the cars actually achieve.

Is the test track ideal setup near to each of the next three race setup?

I believe so. Richard might be able to give some more details on this.

[machin]

Yeah, we specifically picked these 3 tracks because they are so similar in terms of set-up requirements...I just checked and they are so similar I think it would be misleading for me to categorise any one of them as being more less downforce dependent than the others....

If you start with a baseline car having Cl.A of 5 and a Cd.A of 1.5 then an increase in Cl.A of 1.05 is roughly equivalent to a 0.2 decrease in Cd.A in terms of lap time at all 3 of the remaining tracks (and the test track)...it's not quite a linear relationship, but close to...

..or put another way... If you can increase Cl.A by 1.05 without increasing Cd.A by more than 0.2 you'll go quicker, and if you can decrease drag by 0.2 without decreasing Cl.A by more than 1.05 you'll be quicker...

Taking that a stepfurther... You should be looking to remove elements from your cars that have an L/D ratio of less than 5:1 and adding elements that have an L/D ratio of more than 5:1...

Earlier people were talking about wings... I suspect that at high A.o.A some wings have a low L/D (around 3:1 maybe?) but at medium A.o.A probably have L/D of 8:1 or more... So you should be looking to fit a medium A.o.A wing if possible...

I'd agree with Chris: categorising the tracks is really very dependent on the each car... I really would encourage people to play with the test track and do some sort of analysis like I've done on my "CCE LMP1 [KVRC~ish]" topic to really hone in on which set up is best for them....

[machin]

Out of interest does anyone have figures for the downforce and drag they achieved with their rear wing alone from round 3? I'd like to recalibrate my "by-eye" windtunnel

[graham.reeds]

Couple of questions having looked through the first few and last few pages. Is there a setup guide for the needed software? Also are there recommended versions (the version numbers that the race is run on?)

Also where do you get Khamsin from? A google search takes you to Julien de Charentenay homepage which likes to Hibou Scientific which is now defunct. I looked at a couple more hits on google and they take you to either site:-(

I managed to get SketchUp...

[matt21]

I´m not quite sure, if it is written somewhere, but do you require the cars to be done in a specific CAD software?

[CAEdevice]

Hi, there is no need to use a specific software, only a good quality STL format is required (I use Solidworks, some uses Catia, others use SketchUp, ...).
You can find information about the rules, the files to be submitted and the solver (now called One Click CFD) in the official website: http://www.khamsinvirtualracecarchallenge.com/ or just wait for Chirs and Julien on this forum who will help you.

[CAEdevice]

Out of interest does anyone have figures for the downforce and drag they achieved with their rear wing alone from round 3? I'd like to recalibrate my "by-eye" windtunnel

Hi machin, I don't have exact numbers (I'm not able to extract data related to only one component with OCCFD), but my estimation is that the wing I'm going to use for the 4th race has a DF/DRAG ratio around 9 or less. I'll let you know more precise data in the next days.

EDIT: The exact data for the rear wing I'm working on for the low-drag race are:

Drag: 144.6 N
Drag coefficient - Cd: 1.10
Drag area - Cd.A: 0.12 m2
Downforce: -945.20 N
Downforce coefficient - Cl: -7.14
Ratio: 6.5 (much less than I estimed)

[graham.reeds]

Hi, there is no need to use a specific software, only a good quality STL format is required (I use Solidworks, some uses Catia, others use SketchUp, ...).
You can find information about the rules, the files to be submitted and the solver (now called One Click CFD) in the official website: http://www.khamsinvirtualracecarchallenge.com/ or just wait for Chirs and Julien on this forum who will help you.

I can see the rules, but it's getting hold of Khamsin is the issue. I would like to work against whatever will be final test - I have read of competitors getting different results so I would like to replicate the official test to base my design decisions on.

I would love to have a try on Catia or SolidWorks (even looked on ebay for the student version) but I am a software developer by day and have an interest in racing by night. I would like to see if I have a aptitude for design.

[JJR]

Out of interest does anyone have figures for the downforce and drag they achieved with their rear wing alone from round 3? I'd like to recalibrate my "by-eye" windtunnel

For my car downforce to drag ratio was around 5.5 in high downforce trim.

Value around 3 is achived by wing with low aspect ratio ( F1 cars - AR 2 ).I remember study which was publicated in racecar engineering that 2008 value for LMP teams was around 8 in high downforce configuration ( in those days wing dimmension was 2000x300mm - AR 6,7 )

Another study :

ORECA LMP 2009 (from CFD ) - low downforce wing, downforce to drag ratio 9 (1600x250mm wing - AR 6,4).

Pescarolo P03 LM - low downforce wing, downforce to drag ratio around 14 !


Wings with higher aspect ratio ( AR ) are more efficient.

[matt21]

Is there any information what the 2016 challenge would be about?

[RicME85]

Not yet.

[variante]

Not yet.

True, but we're probably heading towards a similar regulations package compared to this year. I.e: LMP like cars, more realism, possibly the choice for a front engine layout.

@matt21: Khamsin is, basically, the predecessor of OCCFD (that you can download from the official KVRC site). I kept using it because it's more flexible compared to the successor, and also because setting up the thing, making it reliable and getting to know how it performs in comparison to the previously acquired data is a bit tricky... These issues aside, OCCFD is the way to go.

About the rear wing: for an aerodynamic element to be productive in the next races an efficiency of at least 5 is required, if I remember correctly. It shouldn't be too hard for a wing to reach that value, however the presence of such element should be balanced by a correspondent element on the front of the car. Now, you should ask yourself: is it worth, efficiency wise, placing a further downforce producing element at the front rather than using that element to help the diffuser producing downforce? Let's remember that a diffuser manages to reach enormous efficiency values...

I do not have the answer, unfortunately, as I don't have time for such analysis.