[MVRC] Mantium Virtual Racecar Challenge 2022 (Grand Prix Cars)

[Dynamicflow]

I copy the link again for simplicity: https://mantiumchallenge.com/cfd-images ... mvrc-2022/

What do you think about? I appeal to professional aerodynamics. I consider Cp_Tot a bit like a measure of the amount of energy present in the fluid: is it better to have still energized air to come out of the diffuser or not?

You are better off increasing the strength of the counter rotating vortices coming out of the diffuser - this would create a drop in static pressure at the diffuser outlet and an increase in underbody mass flow. It is a lot more suitable to look at static pressure and velocity vectors on that plane.

[CAEdevice]

I copy the link again for simplicity: https://mantiumchallenge.com/cfd-images ... mvrc-2022/

What do you think about? I appeal to professional aerodynamics. I consider Cp_Tot a bit like a measure of the amount of energy present in the fluid: is it better to have still energized air to come out of the diffuser or not?

You are better off increasing the strength of the counter rotating vortices coming out of the diffuser - this would create a drop in static pressure at the diffuser outlet and an increase in underbody mass flow. It is a lot more suitable to look at static pressure and velocity vectors on that plane.

Thanks, so less "pressure energy" and more "kinetic energy"

[variante]

Did JJR and Variante receive the correct reports?

No, but that's not very important.

[JJR]

I also didn´t recieved reports but I would like to see them.

[G-raph]

I think the pictures for JJR and Variante are from their first "rogue" CFD runs with the crazy numbers, wrong ground clearance and asymmetric results (as Matteo mentioned). It would be good to get these updated to the proper results, so we can compare everyone properly.

They are and I just fixed this, but you guys were faster than me....

Once again, thank you very much for these pictures, they are very interesting. I'm quite surprised and/or intrigued by some of them.

I'd be happy to comment them all, or answer any question anyone might have, but I understand that so early in the challenge this might not please everyone. Let me know what you think, but given where we are now it might be worth waiting for the Race 2 pictures anyway.

Maybe when we are closer to (or even after) the final race, it might also be useful to see the the same Cp_tot planes further upstream (using the larger scale), to see how the front-end has managed the wheel wake (X=0.533) and what the flowfield looks like under the floor before it enters the diffuser (X=2.967).

I copy the link again for simplicity: https://mantiumchallenge.com/cfd-images ... mvrc-2022/

What do you think about? I appeal to professional aerodynamics. I consider Cp_Tot a bit like a measure of the amount of energy present in the fluid: is it better to have still energized air to come out of the diffuser or not?

You are right, Cp_tot IS a direct measure of the amount of energy present in the fluid.

The honest answer to your question is "it depends". Sorry, I wish there was a simpler solution too!

Ideally, you would have a lot of energy at the back of the diffuser to maximise the space the underfloor massflow can expand into. Think of any very low Cp_tot region as a wall that is blocking massflow at the back of your car, because this is stagnant flow with very low or even 0 velocity.

Having said that, to generate downforce you usually have to spend some energy creating vortices and accelerating the flow under your car surface. So having very clean flow at the back of the diffuser usually means you haven't generated much downforce along the way.

In my experience I would go with something like PurePowerRacing (or myself), but obviously none of us are on the podium. The winner has clearly worked the flow very hard.

The real question is : can you justify all the losses that you have created? Do they come from (for example) a very strong vortex that has genreated very low static pressure under your floor (as suggested by DynamicFlow in his post above)? Or is it just a useless flow separation that is only harming the exit condition at the back of the car (like at the junction between my rear wing and its endplate)?

[variante]

I'd be happy to comment them all, or answer any question anyone might have, but I understand that so early in the challenge this might not please everyone. Let me know what you think, but given where we are now it might be worth waiting for the Race 2 pictures anyway.

Feel free to comment!
Your car surely sticks out the most, especially for the cooling chimneys' wake. But that's good news for you, after all, because with a small fix you can gain a lot of performance on the rear.

[CAEdevice]

The real question is : can you justify all the losses that you have created? Do they come from (for example) a very strong vortex that has genreated very low static pressure under your floor (as suggested by DynamicFlow in his post above)? Or is it just a useless flow separation that is only harming the exit condition at the back of the car (like at the junction between my rear wing and its endplate)?

The car I submitted for Race1 (Hungary) was in the second condition (separation inside the diffuser, in the last 250mm). Vortices are present in the Race2 (Monza) car (they take origin from the strakes) but not strong enough to survive and reach the diffuser. Anyway the separation, still present, is less extended. I expect a good performance improvement, but I am not sure it will be enough for the podium.

[CAEdevice]

Sorry for the lazy user question. I was wondering if it is possible to obtain images with a discrete color scale instead of continuous, directly from MFlow -pp, without going through Paraview.

[LVDH]

Sorry for the lazy user question. I was wondering if it is possible to obtain images with a discrete color scale instead of continuous, directly from MFlow -pp, without going through Paraview.

It actually is. I have not used this option for a while, so I will have to check tomorrow myself, how to use it.


Other than that, I was finally a good boy and updated the page. It now contains results and team pages. Please have a look and find my mistakes. It is a lot of copy-paste work that just invites to get something wrong. At least, I have now automated as much as possible. After the next results are in, a bunch of tables get created automatically that then overwrite what we have now.

Oh, and I will send those two missing reports out tomorrow morning as well.

[CAEdevice]

It actually is. I have not used this option for a while, so I will have to check tomorrow myself, how to use it.
Oh, and I will send those two missing reports out tomorrow morning as well.

Thanks, also for publishing the cars for Monza.
The most promising cars from my point of view are Koldskaal, Variante and Max, with Tolo (best modeling without doubts) and JJR as outsider for the podium.

The question is: who among the top teams has been able to keep the same efficiency with a low downforce setup?

[variante]

Koldskaal has a new diffuser and a smaller rear wing, so i'd expect almost the same downforce and higher efficiency.
Max went for very low downforce and cleaned up his car, so i'd expect lower drag for the same efficiency.
I want to guesstimate a laptime of 79s low for both.
And i think that PurePower will also get about there. With all the others at a close distance.

[G-raph]

Good luck for Race 2 everyone!
As I said before, my money is on Tolo. This car looks like it has got everything right.
But as it is a new entry, maybe it hasn't been as well optimised in CFD as it looks and therefore could let me down! In which case, Koldskaal would be my favourite again.

Feel free to comment!
Your car surely sticks out the most, especially for the cooling chimneys' wake. But that's good news for you, after all, because with a small fix you can gain a lot of performance on the rear.

I'll explain the story and the concept of these chimneys another day, but despite clearly not working as intended I'll stick with them. Partly because I'm stubborn, partly because I don't think they are costing me too much performance compared to the other conventional designs (because the cooling target is very high).

Yes, fixing my rear wing separation (hopefully!) should improve my performance, but I don't think it will be massive as it is only in the outer corner. I feel you have much more to gain than me by fixing your beamwing separation. And I can see you have turned up in Monza with a low drag beamwing.

The car I submitted for Race1 (Hungary) was in the second condition (separation inside the diffuser, in the last 250mm). Vortices are present in the Race2 (Monza) car (they take origin from the strakes) but not strong enough to survive and reach the diffuser. Anyway the separation, still present, is less extended. I expect a good performance improvement, but I am not sure it will be enough for the podium.

Hmm... are you sure you have a diffuser separation? The flow at the exit of the diffuser surface looks very clean to me. I think the loss you see is the diffuser vortex bursting.

And I would not expect the floor fences vortices to survive all the way to the diffuser, given the CFD settings used for the challenge (coarse mesh and rke turbulence model - this is not a criticism btw).

Sorry for the lazy user question. I was wondering if it is possible to obtain images with a discrete color scale instead of continuous, directly from MFlow -pp, without going through Paraview.

It actually is. I have not used this option for a while, so I will have to check tomorrow myself, how to use it.

Good news! I'd be interested in that too.

[LVDH]

OK, so changing the color map for the post-processing is easy. It even works for cases that are already done!
Open the case in the GUI and head over to settings. There you find a setting called cmap_name. Unfortunately my cool GUI has never heard of drop down menus, so you have to enter something valid. At least you can hover with the mouse over the field and see what you could enter. You should see:
rainbow, rainbow_grey, rainbow_desat, miami, blue_black, warm_cool.
So enter something and do not forget to use the "Apply Settings" button.
Now, you can either run a new case or post-process a finished case as you normally do.
For those who are not using the GUI, keep in mind, the GUI only writes a text file solver_settings.ini into the input_files folder. You can create it manually or copy it from other cases. For the color map, it only needs this line:

Code: Select all

cmap_name=rainbow

Again, now you can post-process the case as you wish.
If you guys want new color maps, just let me know, adding them is very easy.

[CAEdevice]

OK, so changing the color map for the post-processing is easy. It even works for cases that are already done!
Open the case in the GUI and head over to settings. There you find a setting called cmap_name. Unfortunately my cool GUI has never heard of drop down menus, so you have to enter something valid. At least you can hover with the mouse over the field and see what you could enter. You should see:
rainbow, rainbow_grey, rainbow_desat, miami, blue_black, warm_cool.
So enter something and do not forget to use the "Apply Settings" button.
Now, you can either run a new case or post-process a finished case as you normally do.
For those who are not using the GUI, keep in mind, the GUI only writes a text file solver_settings.ini into the input_files folder. You can create it manually or copy it from other cases. For the color map, it only needs this line:

Code: Select all

cmap_name=rainbow

Again, now you can post-process the case as you wish.
If you guys want new color maps, just let me know, adding them is very easy.

Thanks it works (without the GUI only in a new case).

If possibile it would be useful a scale with less levels/colors (10 or 12 would be ok)

[Ft5fTL]

What is the latest verdict on wing endplates? Will simplified endplates be mandatory?