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

[machin]

Andre said we should go with one week delay... so you should be getting the 1-week notice E-mail this weekend.... The idea being just to give you some time to do a final CFD run and check your times rather than a complete re-design

[wb92]

Recently from time to time my post-pro doesn't work and it result only in CpT values (at least something) while the rest of the data doesn't want to go through sampleDict, error message below:

• Time = 2000
  
  Reading fields:
  volScalarFields: static(p)_coeff total(p)_coeff
  volVectorFields: U
  
  Executing functionObjects
  --> FOAM Warning :
  From function void Foam::mappedPatchBase::calcMapping() const
  in file mappedPatches/mappedPolyPatch/mappedPatchBase.C at line 604
  Did not find 26064 out of 23754 total samples. Sampling these on owner cell centre instead.
  On patch MVRC_frontwheels on region region0 in mode nearestCell
  with offset mode normal. Suppressing further warnings from mappedPatchBase
  [22] Generating stack trace...
  [22]
  
  Backtrace:
  ZN10StackTraceC1Ev [0x705c1465+0x25]
  module: C:\Program Files\blueCFD-Core-2017\ThirdParty-5.x\platforms\mingw_w64GccDPInt32\lib\libstack_trace.dll
  ZN4Foam5error10printStackERNS_7OstreamE [0x1171c88+0x218]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libOpenFOAM.dll
  ZN4Foam7sigSegv14sigSegvHandlerEi [0x1173883+0x33]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libOpenFOAM.dll
  (No symbol) [0x4045c7]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\bin\postProcess.exe
  _C_specific_handler [0x7ffcbb1a8048+0x98]
  module: C:\Windows\System32\msvcrt.dll
  0_chkstk [0x7ffcbcbc11cf+0x11f]
  module: C:\Windows\SYSTEM32\ntdll.dll
  RtlRaiseException [0x7ffcbcb8a209+0x399]
  module: C:\Windows\SYSTEM32\ntdll.dll
  KiUserExceptionDispatcher [0x7ffcbcbbfe3e+0x2e]
  module: C:\Windows\SYSTEM32\ntdll.dll
  ZN4Foam15mappedPatchBase9facePointERKNS_8polyMeshEiNS1_17cellDecompositionE [0x632cfdee+0x28e]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libmeshTools.dll
  ZNK4Foam15mappedPatchBase10facePointsERKNS_9polyPatchE [0x632d01db+0x9b]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libmeshTools.dll
  ZNK4Foam15mappedPatchBase11calcMappingEv [0x632d488f+0x7f]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libmeshTools.dll
  ZNK4Foam25sampledPatchInternalField16interpolateFieldIdEENS_3tmpINS_5FieldIT_EEEERKNS_13interpolationIS4_EE [0x5b0eb58+0x3d8]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libsampling.dll
  ZNK4Foam25sampledPatchInternalField11interpolateERKNS_13interpolationIdEE [0x5992fbd+0xd]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libsampling.dll
  ZN4Foam15sampledSurfaces14sampleAndWriteIdEEvRKNS_14GeometricFieldIT_NS_12fvPatchFieldENS_7volMeshEEE [0x5a2a51d+0xcd]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libsampling.dll
  ZN4Foam15sampledSurfaces14sampleAndWriteINS_14GeometricFieldIdNS_12fvPatchFieldENS_7volMeshEEEEEvRKNS_12IOobjectListE [0x5a28d70+0x340]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libsampling.dll
  ZN4Foam15sampledSurfaces5writeEv [0x59ba2c7+0x1d7]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libsampling.dll
  ZN4Foam15functionObjects11timeControl5writeEv [0xfc568a+0x4a]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libOpenFOAM.dll
  ZN4Foam18functionObjectList7executeEv [0xfbc3c6+0x76]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\lib\libOpenFOAM.dll
  (No symbol) [0x402c30]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\bin\postProcess.exe
  (No symbol) [0x478f9b]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\bin\postProcess.exe
  (No symbol) [0x4013f7]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\bin\postProcess.exe
  (No symbol) [0x40152b]
  module: C:\Program Files\blueCFD-Core-2017\OpenFOAM-5.x\platforms\mingw_w64GccDPInt32Opt\bin\postProcess.exe
  BaseThreadInitThunk [0x7ffcbaed7bd4+0x14]
  module: C:\Windows\System32\KERNEL32.DLL
  RtlUserThreadStart [0x7ffcbcb8ce51+0x21]
  module: C:\Windows\SYSTEM32\ntdll.dll
  
  job aborted:
  [ranks] message
  
  [0-21] terminated
  
  [22] process exited without calling finalize
  
  [23] terminated
  
  ---- error analysis -----
  
  [22] on DESKTOP-JGS79UG
  postProcess ended prematurely and may have crashed. exit code 3
  
  ---- error analysis -----

any ideas on that one? it happens at random.

[LVDH]

Mapping the fields values to your car surface is failing. This indeed only happens sometimes and is an OpenFOAM issue. This can be because your mesh is too big (open geometry) but more likely because of bad cells somewhere on the car. There is not that much you can do about it. You could try to locate where you have big pressure gradients on you car surface in Paraview to possibly detect where the issue is and fix the geometry. Maybe checkMesh tells you something. You could also try to change the distance slightly in the sampleDict. There are many options, if you really want to fix this I could point out some more options but you would basically have to rerun the entire simulation, as it is pretty much a mesh issue.

[k.ko100v]

Hi Guys,

Something strange happens.

2 days ago, I recieved this kind of cooling flow shape, after designing a brand new diffuser, without any flaps.


I thought that the diffuser is stalling, so I managed to fix it, by slightly changing the shape and adding some flaps to guide the flow inside the diffuser. The flow shape was improved, BUT I lost arround 0.2 Lift and the CoP move to the front by 0.1m



So I am a bit confused...

Has anybody seen something like this?

Regards,
Krasen

[wb92]

Hi Guys,

Something strange happens.

2 days ago, I recieved this kind of cooling flow shape, after designing a brand new diffuser, without any flaps.
https://imgur.com/Cq5TM8Z.jpg

I thought that the diffuser is stalling, so I managed to fix it, by slightly changing the shape and adding some flaps to guide the flow inside the diffuser. The flow shape was improved, BUT I lost arround 0.2 Lift and the CoP move to the front by 0.1m

https://imgur.com/PijJXdd.jpg

I think to fully see what's the cause of such loss you would need to show pressure distribution of your diffuser solutions. interesting would be to see the development of CL over the length of the car (at least on the rear) - then you can specify if it's only diffuser or whole floor issue

So I am a bit confused...

Has anybody seen something like this?

you mean confusing loss of performance? that happens every day
I'm starting to think I was super lucky with previous car

[jjn9128]

Hi Guys,

Something strange happens.

2 days ago, I recieved this kind of cooling flow shape, after designing a brand new diffuser, without any flaps.
https://imgur.com/Cq5TM8Z.jpg

I thought that the diffuser is stalling, so I managed to fix it, by slightly changing the shape and adding some flaps to guide the flow inside the diffuser. The flow shape was improved, BUT I lost arround 0.2 Lift and the CoP move to the front by 0.1m

https://imgur.com/PijJXdd.jpg

So I am a bit confused...

Has anybody seen something like this?

Regards,
Krasen

With any weird result like this check for holes in the mesh. The first case the streamlines look odd. Is there a second set of heat exchangers or some other accident?!?

[yinlad]

Hi Guys,

Something strange happens.

2 days ago, I recieved this kind of cooling flow shape, after designing a brand new diffuser, without any flaps.
https://imgur.com/Cq5TM8Z.jpg

I thought that the diffuser is stalling, so I managed to fix it, by slightly changing the shape and adding some flaps to guide the flow inside the diffuser. The flow shape was improved, BUT I lost arround 0.2 Lift and the CoP move to the front by 0.1m

https://imgur.com/PijJXdd.jpg

I think to fully see what's the cause of such loss you would need to show pressure distribution of your diffuser solutions. interesting would be to see the development of CL over the length of the car (at least on the rear) - then you can specify if it's only diffuser or whole floor issue

So I am a bit confused...

Has anybody seen something like this?

you mean confusing loss of performance? that happens every day
I'm starting to think I was super lucky with previous car

yeah I'm with you. My car for this season is better in almost every way I can imagine, but is performing worse than the car I slapped together in 1 week for the last race of last season.

I'm thinking of running my old car in the new mflow just as a sanity check to see if it returns the same numbers as before, because it was such a pig it shouldn't be anywhere near as good as this new car!

[wb92]

yeah I'm with you. My car for this season is better in almost every way I can imagine, but is performing worse than the car I slapped together in 1 week for the last race of last season.

I'm thinking of running my old car in the new mflow just as a sanity check to see if it returns the same numbers as before, because it was such a pig it shouldn't be anywhere near as good as this new car!

It's same for me, the new car is built much much better, but I can't get any close to the old car, even using same parts of it while checking the same concept.

I haven't run old car 1:1 in new MFlow yet, but that one with new parts (which were supposed to work!)... didn't work so well, so I guess if I would take all old parts it should be fine though...

Question to LVDH: was there any change under the hood of simulation that we could expect different results?

[k.ko100v]

Hi Guys,

Something strange happens.

2 days ago, I recieved this kind of cooling flow shape, after designing a brand new diffuser, without any flaps.
https://imgur.com/Cq5TM8Z.jpg

I thought that the diffuser is stalling, so I managed to fix it, by slightly changing the shape and adding some flaps to guide the flow inside the diffuser. The flow shape was improved, BUT I lost arround 0.2 Lift and the CoP move to the front by 0.1m

https://imgur.com/PijJXdd.jpg

So I am a bit confused...

Has anybody seen something like this?

Regards,
Krasen

With any weird result like this check for holes in the mesh. The first case the streamlines look odd. Is there a second set of heat exchangers or some other accident?!?

Hm, No, the cooling setup is separate file and it is one and the same for both cases. I was wondering how a messy looking flow gives better results, compared to better looking flow and lower results.

I have the assumption that, if any aero element is stalled, it is not aero effective and I espected that after the "corrective actions" the case will be improved. Unfortunately no, but I hope that this is a sign of a good potential

I am testing the case on Mflow from last year. In the current version I miss the "U_nearWalls.vtk" file. I compared the both versions. What I've observed (based on my cases) the newer version is given equal or better results. I would recommend to use the older version for qually

EDIT:

Yeah... it looks like that the diff is stalling (or I am wrong), and somehow the flow is concentrated to the middle of it and makes it stronger



Regards,
Krasen

[variante]

If your parts look better, they probably are. Problem is they're not resonating one another.
For your car to work, you've got to find the keystone of your project and design the parts accordingly.

I'll give you an example: when this challenge was based on LeMans style cars, i found out that my diffuser worked better taking air from the sides rather than from the front of the car. Despite being state of the art, many parts taken from actual LM cars just wouldn't work on my car, due to different philosophies.

Still, i must say that these F1 style cars are much harder to manage and improve than LMPs. The best approach for development is to take little steps and to understand very well what effects each change produces before proceding further.

[spacehead3]

Despite being state of the art, many parts taken from actual LM cars just wouldn't work on my car, due to different philosophies.

That's actually one of the things that I'm finding most interesting about this challenge -- the ways in which our cars are functioning differently from a real F1 car. I always tell Formula SAE students to be very careful looking at "real" race cars for inspiration because the regulations and operating conditions are different.

[jjn9128]

If your parts look better, they probably are. Problem is they're not resonating one another.
For your car to work, you've got to find the keystone of your project and design the parts accordingly.

I'll give you an example: when this challenge was based on LeMans style cars, i found out that my diffuser worked better taking air from the sides rather than from the front of the car. Despite being state of the art, many parts taken from actual LM cars just wouldn't work on my car, due to different philosophies.

Still, i must say that these F1 style cars are much harder to manage and improve than LMPs. The best approach for development is to take little steps and to understand very well what effects each change produces before proceding further.

"Proper" race cars also have to work in a wide range of operating conditions, squat/dive, roll, yaw, steer, crosswinds. A lot of aerodynamic devices are aimed at improving consistency in those conditions. For us with one static attitude and straight ahead only it should be easier but we're all struggling... or at least we're all claiming to struggle

[variante]

True, but that's more a matter of fine tuning parts to work effectively in variety of conditions.
You could use nearly all the parts you see on a F1 car and get positive results out of them as long as your approach to your car is the same used on that F1 car.

or at least we're all claiming to struggle

Naah...i don't think anyone is lying because it's properly hard.
I have improved my car, but i struggled nonetheless. I've managed to improve it mainly because i'm spending way too much time for this competition

[variante]

Yeah... it looks like that the diff is stalling (or I am wrong), and somehow the flow is concentrated to the middle of it and makes it stronger

Definitely stalling. Try a fence, a strake.

[jjn9128]

Naah...i don't think anyone is lying because it's properly hard.
I have improved my car, but i struggled nonetheless. I've managed to improve it mainly because i'm spending way too much time for this competition

I'm legitimately considering sending my PhD back I'm so lost