[MVRC] Mantium Virtual Racecar Challenge 2020 (Grand Prix Cars)

[machin]

Andre can I ask a clarification regarding the warning for CAE(?) for having the exhaust visible when looking through the cooling duct. For me that satisfied the rule about covering the engine but obviously there was a warning.

The requirement is that the parts marked as "internal" need to be fully enclosed by user-bodywork. So just being inside the sidepod (but open to the freestream air) is not allowed. This is to avoid ambiguities and aids with automatic rules checking.

Also for next season can we get a smaller engine template? The current one is annoying me It's so big e.g. this is a comparison to a simplified version of the 1988 Honda V6 placed at a more representative height relative to the plank. The 1988 engine is also 200mm shorter!!

Maybe.. but remember that the "engine" part also includes an allowance for engine-related systems (I think your section is a little unrealistic as it just accounts for the main engine parts, and not, for example exhaust manifolds etc..) also in years past we used to say something like "Realistic space should be provided around the engine part"; obviously "Realistic" is pretty subjective, so now we have a slightly bigger engine model, but you can get as close to it as you want -but it should be enclosed, (see above ). Also; it's the same 'challenge' for everyone....

[machin]

I have just seen the video: it looks very similar to my car, you may be right. Let's wait for André to clarifications.

It was a purposeful tactic to leave team names out of the scrutineering images.... the idea was to try and encourage everyone to check that the types of issues we found in the example images are not present on your own car, whether we showed an image of it or not...

The simple way to check is to have all the MVRC internal parts in one colour, your body work in another colour, and the legality volumes in another... you can then quickly see where the parts are exposed...

[Joe7218]

Hi, when looking at the official results for my car, I noticed the sum of the cl of each individual part was much greater then the total cl given at the top of the document (there was almost a 0.4 cl difference.) there is also a discrepancy between the summed cd values and the total cd value, however the discrepancy is much less (only about 0.08). Does this mean the race results for my car would be wrong? (unless there is supposed to be a discrepancy? thanks

[k.ko100v]

Today I receieved the official Post Process folder. Thank you Andre.

Yes, I sent out the reports. I had to create them with offscreen rendering which somehow deactivates AA, sorry for that.
I hope to get some other open issues tackled tomorrow. Currently I am crazy busy. That is why things like the homepage do not get updated. I hope to compile a small list of open issues where people can help. Some of it is coding scripts to automate the MVRC processes. I think, I will create some kind of Git account where people could contribute, if interested.

Yes I have it, but it stays in "vehicle_body"

Not sure what this means. But if you have the exhaust exit surface in both folders they will be overlapping and the result will be arbitrary. This can mean some elements that are and exhaust and some that are a wall. As the BC is defined with a flow rate, this could cause crazy velocities.

I had only one exhaust out file and It stayed in the "vehicle body" folder. Now i moved it to the "special_bc" folder. Should I expect any performance drop, or increase?

So I added the exhaust_out file to the special_bc folder (only) and here are the results compared to the official ones.


It doesn't looks nice, but if it is not affecting the aero performance I am ok.

[jjn9128]

Andre can I ask a clarification regarding the warning for CAE(?) for having the exhaust visible when looking through the cooling duct. For me that satisfied the rule about covering the engine but obviously there was a warning.

The requirement is that the parts marked as "internal" need to be fully enclosed by user-bodywork. So just being inside the sidepod (but open to the freestream air) is not allowed. This is to avoid ambiguities and aids with automatic rules checking.

Also for next season can we get a smaller engine template? The current one is annoying me It's so big e.g. this is a comparison to a simplified version of the 1988 Honda V6 placed at a more representative height relative to the plank. The 1988 engine is also 200mm shorter!!

Maybe.. but remember that the "engine" part also includes an allowance for engine-related systems (I think your section is a little unrealistic as it just accounts for the main engine parts, and not, for example exhaust manifolds etc..) also in years past we used to say something like "Realistic space should be provided around the engine part"; obviously "Realistic" is pretty subjective, so now we have a slightly bigger engine model, but you can get as close to it as you want -but it should be enclosed, (see above ). Also; it's the same 'challenge' for everyone....

Fair enough. I'd argue it's not open to freestream but cooling flow, but regardless so long as I know the ruling.

I know that "engine" is just a block and doesn't have ancillaries on it but the point was about height. I guess I'm just annoyed I can't get the back as tight as I want. No McLaren size zero for me

[machin]

No McLaren size zero for me

Nor for anyone else, .

I do think that the odd “challenge” here and there is a good thing; in my professional life I’ve always had some little thing imposed on me by other engineering disciplines that I didn’t like but needed to work around (I work as a mechanical engineer in ship propulsion system design, a comparable example is that the ideal engine position is a compromise between the ideal shaftline, hydrodynamic considerations (hull shape), interior space, structural design, etc...), so I see this “Working within the constraints” as part of the challenge and good experience for the budding engineers amongst us (I know we have a mix of people who are already in industry, some who never intend to go into the profession etc, so that might not apply to all).

Nevertheless, we will review the engine model for next year.

[machin]

Hi, when looking at the official results for my car, I noticed the sum of the cl of each individual part was much greater then the total cl given at the top of the document (there was almost a 0.4 cl difference.) there is also a discrepancy between the summed cd values and the total cd value, however the discrepancy is much less (only about 0.08). Does this mean the race results for my car would be wrong? (unless there is supposed to be a discrepancy? thanks

If I remember correctly the list of components below the totals doesn’t include the forces on the heat exchangers... so it doesn’t add up...

I’m not sure why they’re excluded... Andre may be along to comment why soon, but definitely the top line is the correct one to use for the lap time prediction.

[Joe7218]

Hi, when looking at the official results for my car, I noticed the sum of the cl of each individual part was much greater then the total cl given at the top of the document (there was almost a 0.4 cl difference.) there is also a discrepancy between the summed cd values and the total cd value, however the discrepancy is much less (only about 0.08). Does this mean the race results for my car would be wrong? (unless there is supposed to be a discrepancy? thanks

If I remember correctly the list of components below the totals doesn’t include the forces on the heat exchangers... so it doesn’t add up...

I’m not sure why they’re excluded... Andre may be along to comment why soon, but definitely the top line is the correct one to use for the lap time prediction.

Thanks for the clarification

[LVDH]

How different are your results from the official ones? I am a bit confused. I ran the exact car I submitted with MVRC Long template (5000 iterations) and my results are notably different from the official ones:

Personal Pc:
Cd Cl Cl/Cd Cl(f) Cl(r) CoP Intake Exhaust Cooling
Total 1.305 -2.384 -1.827 -1.179 -1.205 1.718 5.56 -1.2979 3.12139

Official:
Cd Cl Cl/Cd Cl(f) Cl(r) CoP Intake Exhaust Cooling
Total 1.319 -2.431 1.715 4.62 -0.392 2.383

Is there any difference between our solver settings and the official one? This is almost a 1.5s difference in lap time and 4 positions... Still 1.5 seconds off pace though haha

So, I checked your logs. You seem to have an interesting machine at your disposal. It looks like, we are not comparing the same case though. You have some different geometry from what is in the official run, resulting in different meshes. This explains why you get slightly different Ci values (I suppose the design is not very different in the two cases). The difference in cooling flow is pretty sure an incorrect tessellation, which I fix for everyone automatically.

Yes, I sent out the reports. I had to create them with offscreen rendering which somehow deactivates AA, sorry for that.
I hope to get some other open issues tackled tomorrow. Currently I am crazy busy. That is why things like the homepage do not get updated. I hope to compile a small list of open issues where people can help. Some of it is coding scripts to automate the MVRC processes. I think, I will create some kind of Git account where people could contribute, if interested.




Not sure what this means. But if you have the exhaust exit surface in both folders they will be overlapping and the result will be arbitrary. This can mean some elements that are and exhaust and some that are a wall. As the BC is defined with a flow rate, this could cause crazy velocities.

I had only one exhaust out file and It stayed in the "vehicle body" folder. Now i moved it to the "special_bc" folder. Should I expect any performance drop, or increase?

So I added the exhaust_out file to the special_bc folder (only) and here are the results compared to the official ones.


It doesn't looks nice, but if it is not affecting the aero performance I am ok.

After loading the case in the GUI, you should be able see visually inspect the surface, I think it should be pink and not blue like the other car parts. You seem to have something else overlapping the part.

Hi, when looking at the official results for my car, I noticed the sum of the cl of each individual part was much greater then the total cl given at the top of the document (there was almost a 0.4 cl difference.) there is also a discrepancy between the summed cd values and the total cd value, however the discrepancy is much less (only about 0.08). Does this mean the race results for my car would be wrong? (unless there is supposed to be a discrepancy? thanks

If I remember correctly the list of components below the totals doesn’t include the forces on the heat exchangers... so it doesn’t add up...

I’m not sure why they’re excluded... Andre may be along to comment why soon, but definitely the top line is the correct one to use for the lap time prediction.

Yes, the single parts do not contain the forces of the porous parts. You should also check if really every single part is listed in the report. In earlier versions, I did not list very many parts on purpose, after more and more complaints and questions about this, I included more. I am not sure if every part is now part of the force per part list.



Also GCBB sent me stl files of the cooling monitoring surface. The mistake made there is that there is one stl file for the monitoring surfaces on the right and left hand sides of the car. This is not good, as we only run a half model. This means there is monitoring surface that is not part of the flow domain. OpenFOAM measures strange stuff, when you do that. Newer versions are even crazier, as they do not measure ridiculous numbers anymore so you might actually trust them, which seems to have happened here. You should either only create a surface for the right hand side of the car or have a separate surface for each side.

[AratzH]

How different are your results from the official ones? I am a bit confused. I ran the exact car I submitted with MVRC Long template (5000 iterations) and my results are notably different from the official ones:

Personal Pc:
Cd Cl Cl/Cd Cl(f) Cl(r) CoP Intake Exhaust Cooling
Total 1.305 -2.384 -1.827 -1.179 -1.205 1.718 5.56 -1.2979 3.12139

Official:
Cd Cl Cl/Cd Cl(f) Cl(r) CoP Intake Exhaust Cooling
Total 1.319 -2.431 1.715 4.62 -0.392 2.383

Is there any difference between our solver settings and the official one? This is almost a 1.5s difference in lap time and 4 positions... Still 1.5 seconds off pace though haha

So, I checked your logs. You seem to have an interesting machine at your disposal. It looks like, we are not comparing the same case though. You have some different geometry from what is in the official run, resulting in different meshes. This explains why you get slightly different Ci values (I suppose the design is not very different in the two cases). The difference in cooling flow is pretty sure an incorrect tessellation, which I fix for everyone automatically.

Interesting machine indeed. Also interesting electricity bill

Could you point what parts where different? I thought I had run the exact files on the zip I uploaded.

Regarding the monitoring surfaces, could you share the exact tessellation settings so I can replicate them?

Thanks!

[cecca98]

Also GCBB sent me stl files of the cooling monitoring surface. The mistake made there is that there is one stl file for the monitoring surfaces on the right and left hand sides of the car. This is not good, as we only run a half model. This means there is monitoring surface that is not part of the flow domain. OpenFOAM measures strange stuff, when you do that. Newer versions are even crazier, as they do not measure ridiculous numbers anymore so you might actually trust them, which seems to have happened here. You should either only create a surface for the right hand side of the car or have a separate surface for each side.

Thanks! That explains everything.
We will check if the difference in values is deriving just from that (hopefully) and work on a better configuration.

[k.ko100v]

I had only one exhaust out file and It stayed in the "vehicle body" folder. Now i moved it to the "special_bc" folder. Should I expect any performance drop, or increase?

So I added the exhaust_out file to the special_bc folder (only) and here are the results compared to the official ones.
https://imgur.com/RMJZIt2.jpg

It doesn't looks nice, but if it is not affecting the aero performance I am ok.

After loading the case in the GUI, you should be able see visually inspect the surface, I think it should be pink and not blue like the other car parts. You seem to have something else overlapping the part.

After loading the case in the GUI, the exhaust surface is visible in yellow color, the same color as the inlet surface.

[LVDH]

So I added the exhaust_out file to the special_bc folder (only) and here are the results compared to the official ones.
https://imgur.com/RMJZIt2.jpg

It doesn't looks nice, but if it is not affecting the aero performance I am ok.

After loading the case in the GUI, you should be able see visually inspect the surface, I think it should be pink and not blue like the other car parts. You seem to have something else overlapping the part.

After loading the case in the GUI, the exhaust surface is visible in yellow color, the same color as the inlet surface.

Should be green (maybe with a touch of yellow).

Could you point what parts where different? I thought I had run the exact files on the zip I uploaded.

Regarding the monitoring surfaces, could you share the exact tessellation settings so I can replicate them?

Thanks!

Uniform triangles with about 5mm side length. Please also keep in mind to have the normals point into the same direction and do not use overlapping elements.



I just sent out the reminder email for the next submission. I totally forgot about this once more. If someone is as surprised as I am, please consider the late submission option.

[etsmc]

are we still submitting predicted lap times?
Good luck everyone, looking forward to seeing developments.

[LVDH]

are we still submitting predicted lap times?
Good luck everyone, looking forward to seeing developments.

Yes, please submit them.