Khamsin Virtual Racecar Challenge 2015

[CAEdevice]

http://i.imgur.com/0tecs1X.png

Those who have used OCCFD, when opening the results in Paraview, did you find the model to no be smooth?
Mine looks like it has lots of dents in it. I assume it is just a lower quality setting in OCCFD for speed and ease of use?

It looks like a refinement issue. Something like this happened in my private tests with OCCFD. It is certainly related to the loss of df.

[cdsavage]

Out of curiosity would anyone be able to work out what my lap time would have been if i had enough rear downforce to balance out the car? Mine is the Mercury motorsports car.

Your car:
Cl.A = 1.08
Cd.A = 1.12
COP = 1.342m

Front Cl.A = 0.5969

We need (front Cl.A)/(total Cl.A) = 0.45 for a COP of 1.65m. Assuming front Cl.A remains unchanged and we increase rear Cl.A, rear Cl.A (new) = 0.7295, for a total Cl.A (new) of 1.3264.

If we also assume that the L/D remains unchanged from your original entry (which probably wouldn't be the case), then the Cd.A (new) = 1.3755.

This produces a lap time of about 397 seconds, less than 1s improvement over the original design.

[cdsavage]

My car is so useless
Good job I have MK2 in the works

It's possible that something weird happened with the simulation for your car, I want to double check this. I marked your result as 'provisional' for the time being.

Anything come of this?

There was an issue with the simulation for your car - there were holes which meant the volume inside the sidepod was meshed. The problem might be due to issues with the STL geometry that you submitted, or it might be due to the repair process on our end. I'm looking at it with Julien, but for the time being, I would suggest the following to anyone modelling in Sketchup or similar programs:

• Make sure there are no holes in the geometry (other than the symmetry plane) - the model should form a single, watertight volume (when considering the body, wings and inlets/outlets together).
• Avoid intersecting geometry, and remove as much of the internal geometry as possible. Only the external surfaces should be present.

The divergence issue in OCCFD is probably due to issues with the input geometry. If you can open the unfinished simulation files in Paraview, see if you can identify an area of extremely low or high pressure (use 'rescale to data range' button), this should give you some clues as to where to start modifying the geometry.

[cdsavage]

Here are some images of the front-end design on each of our podium finishers from round 1, showing velocity. The colour scale and the location of the slice plane is the same across all 3, but when comparing between them, keep in mind that the velocity might not be representative due to the presence of other geometry close to the slice plane (strakes, etc).

CAEdevice:


JJR Racing:


Variante:

[cdsavage]

Some extra images from the top 3 -

CAEdevice:



JJR Racing:



Variante:

[CAEdevice]

How many details !!!

Great renderings!

[machin]

Very good... And in fairness, this second post gives no more away than you would be able to get from a good set of photographs from on-track action at a real race so I think it is fair enough to show them.

EDIT: Can you get them on the @KVRC01 twitter feed?

[cdsavage]

Rear wings -

CAEdevice:


JJR Racing:


Variante:

[RicME85]

Wow, JJR's main plane is a deep dish :O

[CAEdevice]

It seems that CAEdevice rear wing has been sectioned near the external

[julien.decharentenay]

@RicME85 I will be rerunning your simulation tomorrow evening...

I wanted also to mention that my laptop does not have enough grunt to open the final CFD models in ParaView... It is not making things very easy for me...

[RicME85]

I feel we should all chip in to buy Julien a new PC

[cdsavage]

It seems that CAEdevice rear wing has been sectioned near the external

The slice plane was the same for all 3 (X=500mm I think). In your case, it appears that the wing element covering the rear suspension is having a detrimental effect on the rear wing.

[CAEdevice]

It seems that CAEdevice rear wing has been sectioned near the external

The slice plane was the same for all 3 (X=500mm I think). In your case, it appears that the wing element covering the rear suspension is having a detrimental effect on the rear wing.

During the last days before the race I exaggerated with the exit angle of that profile looking for the maximum downforce, without checking it with a simulation! For the next race I'll be back to the original geometry, looking for DF elsewhere.

[RicME85]

Got results back from Julien just now.

Run 1 results:


Run 2 results: