Khamsin Virtual Racecar challenge 2013 (CFD model racing)

[wigglez28]

Personally I completely redesigned my front and rear wings after my calamity of a race in mangy cours. Also I designed a new nose and removed some minor turning vanes.

[machin]

Well, I've made a chart a bit like the one Andy posted for silverstone.... However you should note that the lap times indicated in the chart were achieved with a COP of 1.83m, i.e. balanced in accordance with the mass distribution mandated by the FIA. If your design doesn't have a COP of 1.83m then the lap times will be different.



I've also added a line showing the sort of lap times that the KVRC cars from Magny Cours would achieve, if they had a COP of 1.83m.

[machin]

And another chart showing the affect of COP changes on lap time (if drag and lift coefficients stay the same):-



i.e. aim for a COP of 1.83m for the best lap time

[astracrazy]

so is that graph showing that a low df (not as low as monza) config is better?

[andylaurence]

Interesting. As downforce and drag increase, the l/d ratio becomes more important. For example, the 1:33 lap can be achieved with -ClA of 1.75 and CdA of 1.04, which is a -L/D of 1.68. The same lap time can be achieved with -ClA of 2.75 and a CdA of 1.42, which is a -L/D of 1.94. Clearly, this is shown by the curvature of the line on the graph. As downforce grows, the drag becomes the dominating factor. I wonder how the trend establishes itself over a wider range of drag/downforce/times.

[machin]

so is that graph showing that a low df (not as low as monza) config is better?

Its definitely worth bearing in mind the dotted line showing the sort of aero figures achieved by the cars submitted for Magny Cours... notice how the cars with low downforce (left end of the dotted line) are also the cars with the worst L:D. and a higher (slower) Silverstone lap time. The cars with the highest downforce also achieved the best L:D, and accordingly a better lap time.

It makes sense that a higher downforce configuration would be more efficient... up to a point. if you take the extreme example of an F1 car with no wings it will still create a lot of drag (mainly by virtue of the un-faired tyres), and no downforce... Wings are fairly efficient downforce generators, so the more wing you add the more downforce you generate, but only for a (relatively) smaller increase in overall drag, hence an improvement to overall L:D.

It will be interesting to add in the Monza cars to this chart to see what sort of L:D people have achieved when they are searching for a low downforce set-up...

But at the moment I'd say go with a high Downforce set-up.

[astracrazy]

thanks machin i understand now, originally i didn't understand the graph but now i do it makes sense. Your explanation just now makes even more sense.

For reference, please could you do a similar graph for monza to compare?

its also interesting actually just how important it is to get cop on the bubble

[machin]

Similar chart for Monza, again all results with COP=1.83m.



Notice how the lap time curves are much flatter this time showing that the lap time is heavily dependant on drag and less so by downforce. (As you can guess; for a track like Monaco the lap time curves will be much steeper showing the lap time is much more dependent on downforce and less affected by drag).

Its also interesting to note the "Magny-Cours results curve".... Assuming all designs had a better balance they would've achieved very similar lap times (around 1:26). This confirms that it is possible for the current style of F1 car to lap Monza quickly with a low downforce or a medium downforce set-up (as RedBull did last year).

[stez90]

Machin can you post those plots with the same scale in x and y? Just for better understanding lines slope.

[machin]

Sorry Stez I'm away from my computer for a few days... however, all is not lost; notice how the 1:26 lap line at Monza very closely matches the dotted KVRC line? Well that same dotted line is shown on the Silverstone graph, so you can clearly see the relative differences in the slopes of the two charts.

[julien.decharentenay]

Richard, great work. I really like the simplicity of the graphs. Adding the Silverstone laptime based on the Monza design will (hopefully) allow the team to work out whether to focus on downforce/drag ratio and/or balancing. But, remember that this information will be provided in the feedback sheets only.

Some news: all the simulations have run and post-processed - to the exception of the KVRC showcar. I will be generating pictures tomorrow, doing some last minutes checks, uploading the simulations results and sending out links to download them. Nick is checking the regulations. So it looks under control.

[CottrellGP]

Hi all could someone clarify the outlet regs with me, the rules say that they should be parallel to the rear wheel centre line, does this mean i cannot do the some outlet idea like the one under the Renault logo on the Red Bull?

[N12ck]

ahh, parallel to the rear wheel centre line means, it can be anywhere on the car behind the engine but must be in the yz plane and vertical (not angled), that's what the aim of the wording 'parallel to the rear wheel centre line' it does not mean the outlet has to be on the rear wheel centre line

so in response to your query, those outlets are legal, as long as they are vertical and not angled

[cdsavage]

ahh, parallel to the rear wheel centre line means, it can be anywhere on the car behind the engine but must be in the yz plane and vertical (not angled), that's what the aim of the wording 'parallel to the rear wheel centre line' it does not mean the outlet has to be on the rear wheel centre line

so in response to your query, those outlets are legal, as long as they are vertical and not angled

The F1 rules dont allow openings to be placed just anywhere, they have to be behind a point 55mm forward of the rear wheel center line. Its covered in 3.8.4 (the bodywork minimum radius section). The exceptions are the 25mm either side of the car centerline, and openings for suspension etc (which the openings on the red bull in that pic fall under).

[N12ck]

ahh, parallel to the rear wheel centre line means, it can be anywhere on the car behind the engine but must be in the yz plane and vertical (not angled), that's what the aim of the wording 'parallel to the rear wheel centre line' it does not mean the outlet has to be on the rear wheel centre line

so in response to your query, those outlets are legal, as long as they are vertical and not angled

The F1 rules dont allow openings to be placed anywhere, its covered in the bodywork minimum radius section. The exceptions are the 50mm of the car on the centerline, and openings for suspension (which the openings on the red bull in that pic fall under).

I know this, KVRC runs off loose f1 regulations as it would be impossible to test for every regulation due to time and also due to differing modelling skills and this is why I have said, anywhere but behind the engine to simplify this for this competitions purpose