[KVRC] Khamsin Virtual Racecar Challenge 2016

[machin]

I can't find anything in the real LMP1 rules, but this interview (admittedly old, but still the right sort of car), suggests we may actually be a bit too LOW at the rear:

“With the LMP 900s, you had to be very careful when setting the rake of the cars. Typically you’d see ground clearance of 30mm at the front and 75-80 at the rear"

From http://archive.dailysportscar.com/subsc ... mcneil.htm

Re. The radiators: I was just having a play with Chris' class B car and the the 230,000 doesn't look too bad (with the radiator leant over to the max allowed).... Maybe someone could do 3 different models with rads of that size, but leant over at say 30, 45, 60 degrees from vertical, so we can all see what the side pods would look like at each of those angles?

[CAEdevice]

I can't find anything in the real LMP1 rules, but this interview (admittedly old, but still the right sort of car), suggests we may actually be a bit too LOW at the rear:

“With the LMP 900s, you had to be very careful when setting the rake of the cars. Typically you’d see ground clearance of 30mm at the front and 75-80 at the rear"

But does he talk about static or dynamic height? Our 45mm are measured at 44.7 m/s (and 9000N of df). At the front we run 15 higher actually.

Anyway: I imagine things are quite different if we have to do with a rake setup.
Our floor is running parallel to the ground (btw: it would be very interesting a rake setup for KVRC cars... I guess: front 35mm, rear 55mm).

[machin]

Well he does go on to say:

" if the rear was reduced – to reduce drag, say by fitting soft rear springs or reducing ride height – as we’ve seen, you could get into trouble."

So it sounds like he's talking about dynamic heights.... Given that ....a 45mm front and rear seems like a good compromise...?

[CAEdevice]

Well he does go on to say:

" if the rear was reduced – to reduce drag, say by fitting soft rear springs or reducing ride height – as we’ve seen, you could get into trouble."

So it sounds like he's talking about dynamic heights.... Given that ....a 45mm front and rear seems like a good compromise...?

From an aero point of view, a rake set up and a parallel to ground setup are different concepts, it is not possible to compare. In a rake setup the floor works like a diffuser with a very small angle.

Puting aside the floor height discussion: what about my proposal to merge cooling opt1 and cooling opt2 (see above)? Time before the first race is not very much and it seems to me a good compromise between design freedom and simulation simplicity.

[machin]

Well it seems like a good compromise to me: Option 1 should remain as it is and option 2 changed to be an "Option1+", where the competitor must model the duct...

..... But how do the other competitors feel as I think Option 2 was really added at the request of you guys...

[CAEdevice]

Well it seems like a good compromise to me: Option 1 should remain as it is and option 2 changed to be an "Option1+", where the competitor must model the duct...

..... But how do the other competitors feel as I think Option 2 was really added at the request of you guys...

Yes I was one of the partecipants that required opt2. It actually gives a mich more realistic design and the possibility to include the duct design introduces more design freedom (that is important, because it think the there is the risk for the best 3 teams to converge to similar efficiency, even below the numeric accuracy of the results).

... but at that time we could not imagine the difficulties that Julien would have met. I could simulate the heat exchanger defining the poruos media in 20 minutes with KARALIT CFD (the same, I think, AaratzH with SWX Flow Sim and Mantium with OpenFoam) but to write a framework for Windows seems to be complicated. I think that Julien is making a too heavy job alone.

That is why I would accept the opt1+ compromise for this year (maybe for the first 2 races only?), also considering that we have about one month to complete the car design and we actually need the definitive rulebook. For the same reason I would accept to keep the ride height as it is, waiting next year to discuss about it.

[SR71]

My first simulation...

Now I just need to learn what this means





SR71

[CAEdevice]

You should include a legend: are you showing pressure or velocity? Wich scale range did you use? There is something strange with the diffuser, are you sure that the car is correctly oriented?

If the first picture is representing pressure, it is quite strange the high pressure inside the diff and under the rear wing.

[SR71]

You should include a legend: are you showing pressure or velocity? Wich scale range did you use? There is something strange with the diffuser, are you sure that the car is correctly oriented?

If the first picture is representing pressure, it is quite strange the high pressure inside the diff and under the rear wing.

This is just one of the images from the HTML file generated by one-click. the scale is +/= 1000

I have no idea how to access the flowlines in paraview unfortunately.

SR71

[CAEdevice]

Can you zip the html and image folder and send it to me? (I'm sending my email by PM). Only if you are sure to show your geometry.

[LVDH]

... but at that time we could not imagine the difficulties that Julien would have met. I could simulate the heat exchanger defining the poruos media in 20 minutes with KARALIT CFD (the same, I think, AaratzH with SWX Flow Sim and Mantium with OpenFoam) but to write a framework for Windows seems to be complicated. I think that Julien is making a too heavy job alone.

Not very difficult in OF. I do not think those are among Julien's problems. And with your suggestion we enforce a mass flow with the boundary condition. The nice thing with porous media is that we are in charge of getting the air nice and clean through there - nothing artificial anymore.

[LVDH]

Now I just need to learn what this means

That means that your challenge has started. You have a lot of work ahead of you.

Legends would help us a lot to understand better what is happening. The first one, I guess, shows the pressure distribution on you car's surface. Blue should indicate low pressure. So infront of your diffuser it should be dark blue and in the duffuser light blue. Why yours is red is a good question. The design does not look terribly wrong. Maybe the simulation did not converge. You should have a look at your residual and force curves plotted against the iterations. The residuals should somewhat smoothly go below a threshold like 1e-3. Your forces should smoothly and then flat converge towards some value. If it is fluctuating like crazy you have a problem.

The histogram plot shows the chunks of forces acting on your car, here in X-direction. You should get one for drag and one for down force. In this case I am not sure which you are showing as your red diffuser is a bit confusing. In any case you will see a nice, high tower around your rear wing. It will create a lot of down force but also drag.
Maybe you could create a new thread about your car. Last year we helped, I think RicME, a lot in his own thread on his car got much better and it is fun for everyone to help and know everything better.

[LVDH]

Now I just need to learn what this means

That means that your challenge has started. You have a lot of work ahead of you.

Legends would help us a lot to understand better what is happening. The first one, I guess, shows the pressure distribution on you car's surface. Blue should indicate low pressure. So infront of your diffuser it should be dark blue and in the duffuser light blue. Why yours is red is a good question. The design does not look terribly wrong. Maybe the simulation did not converge. You should have a look at your residual and force curves plotted against the iterations. The residuals should somewhat smoothly go below a threshold like 1e-3. Your forces should smoothly and then flat converge towards some value. If it is fluctuating like crazy you have a problem.

The histogram plot shows the chunks of forces acting on your car, here in X-direction. You should get one for drag and one for down force. In this case I am not sure which you are showing as your red diffuser is a bit confusing. In any case you will see a nice, high tower around your rear wing as it should create a lot of down force but also drag.
Maybe you could create a new thread about your car. Last year we helped, I think RicME, a lot in his own thread on his car got much better and it is fun for everyone to help and know everything better.

[LVDH]

After having a second look at your pictures I suspect your car is going backwards.

[RicME85]

It is