[MVRC] Mantium Virtual Racecar Challenge 2018

[LVDH]

Ok, the numbers are on the challenge page now.
I will not get the CFD reports out this week. I hope this is no big deal as the next race will not be that soon.

I had enough on my tests but i guess my gamble of changing the rake without testing had an impact to the cooling.

I will have to check this. Would be kind of bad if this affects the results so much. Please also keep in mind that I run the simulations for 5000 iterations which is not a default in your settings in MFlow. On some cars some values converge soooo slow it is incredible. It is something I am working on and you can expect an update on all this next month. Finding good mesh settings that work well with all of your very different cars is pretty hard. And a good mesh is the key to good simulations.

[CAEdevice]

Ok, the numbers are on the challenge page now.
I will not get the CFD reports out this week. I hope this is no big deal as the next race will not be that soon.

I had enough on my tests but i guess my gamble of changing the rake without testing had an impact to the cooling.

Please also keep in mind that I run the simulations for 5000 iterations which is not a default in your settings in MFlow. On some cars some values converge soooo slow it is incredible.

Hi, did you run 5000 iterations for all the cars? This could be a good reason to explain the difference I have noticed looking at the number ( efficiency 6.6 instead of 6.8 ). It is clearly not a problem because it is a difference randomly distributed between all the partecipants, but if we need to run more iterations in order to have the same results of the offical solution, I will do (I already play with the number of iterations): the first three teams are so near that I think our distance is less than the convergence tolerance, and it will be even more important in the future because we are all playing with vortices (Variante with his front vortex generators, but also my floor slots work with small vortices).

[LVDH]

Ok, the numbers are on the challenge page now.
I will not get the CFD reports out this week. I hope this is no big deal as the next race will not be that soon.

I had enough on my tests but i guess my gamble of changing the rake without testing had an impact to the cooling.

Please also keep in mind that I run the simulations for 5000 iterations which is not a default in your settings in MFlow. On some cars some values converge soooo slow it is incredible.

Hi, did you run 5000 iterations for all the cars? ...

Yes for all cars. I am in the process of improving the OF settings in MFlow to get better and faster convergence. This is a long ongoing effort and the new teams this season threw new issues towards me. But I am close to getting done. Next year with the F1 rules we will then see how good this all was. You should expect a big update in the next few weeks. For now, you could just set the number of iterations to 5000.

[Ft5fTL]

Well i had around 4.5 Cl/Cd on my fast setting tests so im happy with the results on aero side. On the cooling side, it was on the limit (around 1.51 on single side). I'm afraid i don't have the hardware for 5000 iteration simulations.

[CAEdevice]

I'm afraid i don't have the hardware for 5000 iteration simulations.

I think almost nobody can wait 16-20hour, but most of the development can be done with no more than 2000 iterations. My advice, is to run with about 2000 iterations and (if possibile) to do only a final refinement with 5000 iterations.

[etsmc]

I have been working on some development and I had a bit of spare time.
So, I thought to my self what would happen if the car had some proper wheels?? how would a simulation like it? baring in mind I have no idea how the CFD simulation works I just press the go button on MFlow.

Here is how it went:
I created some simple 5 spoke designed wheels and replaced the centre of the supplied wheels with my 5 spoke design keeping the tyre exactly the same, built the case and started it running.
I keep an eye on my simulations as I like to watch the number come up on screen.
Everything looked ok numbers were coming up similar to what they had with the supplied wheels. I have a few monitoring surfaces and the flow through these was similar also. then it got to about iteration 740 and the cl(r) started to climb, get to the end of the simulation and I have the following numbers
cd 0.39
cl -14.7
cl/cd -37.1
cl(f) -0.7
cl(r) -14.0
cop 2.85

compared to my previous run with the supplied wheels
cd 0.93
cl -3.8
cl/cd -4.1
cl(f) -1.5
cl(r) -2.3
cop 1.79

Just thought it was interesting that wheels made a difference like this. I will try an get some images up like the inside of the diffuser is just all white
for a laugh, I pumped the numbers into the virtual stopwatch and got the following lap times
Lemans 195.94
Sepang 101.77
Sao Paulo 76.96

was fun.

[variante]

The simulation did not converge. Did not go well.

The settings we're using for the wheels don't actually simulate wheel rotation; instead, they are set to impress velocity to the surrounding air. This system is good as long as the wheel is a solid of revolution.

Rim spokes actually move air like fan blades (so they don't simply drag along air due to viscous effects, as a solid of revolution does). A different approach is required to properly simulate this condition, such as a moving mesh.

This doesn't mean that you cannot put spokes in our simulations, but it surely won't be reliable and, in the worst case, it won't converge.

BTW I don't think spokes make much of a difference anyway.

[CAEdevice]

Hi everybody,

after the last two disappointing races I am working on a parallel project (I resume the development after overcoming the disappointment, hoping that Variante is relaxing meanwhile).

I would like to print a 3D version of my car (1:10, or 1:18) and I am looking for components like engine, gearbox, brakes, heat exchangers.
I think I will have to model most of them, but du you have any advice? Wich kind of engine should I use? I am looking for some ideas on GrabCAD.

[Team_Bart]

Hi guys,

A bit late, but I'm really happy with the results last race! The data was expected, but I didn't expect to be on top of the second group Variante, congratulations with the second consecutive win! Also it is cool there are 2 groups really close together, which I think makes it more fun for all of us!
Let's see what the second half of the season brings us, I'm very curious about how the cars and aproaches will changes. Especially what are the top teams doing different in their designing compared with the efficiency tracks? I already have some idea's how to make the ButterFly ready for those tracks, but since I moved last month I had no time to model them yet.


@LVDH, I'm still quite new in this OpenFoam stuff, but when I was doing some tutorials, I "learned" it was possible to use old data as an initial guess for a new simulation. Anyway this was for a simple square box or something. Now I'm reading the iterations discussion above, I was thinking isn't it possible to apply this technique on our cars to reduce convergence time during development? Since most often 90% of the car will be exactly the same as for the previous simulation, this will be a quite good guess to start the simulation with. Anyway I don't know if it is technically possible to implement it on such difficult geometries as ours.

[machin]

I would like to print a 3D version of my car (1:10, or 1:18) and I am looking for components like engine, gearbox, brakes, heat exchangers.
I think I will have to model most of them, but du you have any advice? Wich kind of engine should I use? I am looking for some ideas on GrabCAD.

Have you thought about buying an existing model kit and then just 3D printing the bodyparts you need? For example I have a nice Tamiya McLaren Formula 1 car which has lots of nice bits (engine, gearbox, wheels, tyres, suspension, etc); that would make a nice starting point...?

[machin]

So, for a bit of inspiration for you guys, has anyone thought about trying out an “infinity wing”?

.

[CAEdevice]

I would like to print a 3D version of my car (1:10, or 1:18) and I am looking for components like engine, gearbox, brakes, heat exchangers.
I think I will have to model most of them, but du you have any advice? Wich kind of engine should I use? I am looking for some ideas on GrabCAD.

Have you thought about buying an existing model kit and then just 3D printing the bodyparts you need? For example I have a nice Tamiya McLaren Formula 1 car which has lots of nice bits (engine, gearbox, wheels, tyres, suspension, etc); that would make a nice starting point...?

Do you think that a F1 v8 engine (including kers) plus gearbox would be realistic on our cars?

[CAEdevice]

So, for a bit of inspiration for you guys, has anyone thought about trying out an “infinity wing”?

Not a bad idea, but we should consider that our front wings can't extend outside the maximum width, so we will need to place them forward the front fenders.

By the way: I have no started the high downforce development, but (I know LDVH will be happy about it) I am going to fine tune the same old car I have been using since 2016.

[machin]

Do you think that a F1 v8 engine (including kers) plus gearbox would be realistic on our cars?

For a model; yeah, why not? But the main reason is it will save you a whole load of hassle...!!!

[machin]

Not a bad idea, but we should consider that our front wings can't extend outside the maximum width, so we will need to place them forward the front fenders.

Good point... that won’t really work then; the infinity wing makes use of the lateral flow around the fenders... something more like these end plates on the Pikes Peak Peugeot 206 then...