CFD Modelling

Apart from the 152 and 172, are there any other planes using the new CFD modelling ?

My understanding of it from Asobo is that the implementation of it isn’t too difficult. You would have thought 3rd party developers would be implementing it.

Can we look forward to planes advertising " CFD compliant" ?

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152 is news to me. I think it is only the 172 G1000 version. I don’t follow what is going on with addons.

There is a list maintained by the community here:

I can’t speak to the third-party list, but I will vouch that for base sim aircraft, right now it’s the Cessna 152, 172 G1000 only (the steam gauge one has not been migrated yet), Caravan, and King Air.

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The 172 is the only one in the list with the full CFD implementation, the rest only have the updated Propeller Simulation.

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The impression I got from Asobo was that it was a “easy” thing for developers to apply. I was expecting a quicker uptake on this than what we have had so far, even by Asobo. Must have misunderstood what they said. :roll_eyes:

Applying it is “easy” in the sense that they just have to add a few lines to the flight_model.cfg, but then they have to completely retest and re-tune the whole flight model to get things working as they want.

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Here’s some freeware with CFD:

  • Carbon Cub
  • Savage Grravel
  • Monster NXCub
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It would be a whole lot easier if it were documented in the SDK somewhere. I assume its a little more complicated than simply CFD_EnableSimulation = 1

As luck would have it, I kept a backup copy of the old AS1000 172, but its very old, from 13/04/2021. I wish I had one more recent than that. In any case I can see a lot of differences between the two, other than the CFD additions.

This entire chunk has been removed from the latest version:

fuselage_rigidity = 30
elevator_lift_coef = 3.75
rudder_lift_coef = 2.5
fuselage_lateral_cx = 0.5
aileron_up_drag_coef = 0.5
aileron_down_drag_coef = 1.5
presspt_fwd_Alpha0_pMAC = 0.0
presspt_fwd_AlphaStall_pMAC = 0.1
presspt_fwd_AlphaHiStall_pMAC = -0.25
StallDef_StartRatio = 0.9
StallDef_EndRatio = 1.4;
StallDef_CurvePower = 1.1;
StallDef_minTransition = 0.025;
StallDef_airflowdetachspeed = 10
StallDef_airflowattachspeed = 10
Stall_AileronAddIncidence = 1
Stall_TipAddIncidence = 2.0
Stall_TipAddTwist = 5
Stall_TipTwistScaleRatio = 1.0

Seemingly with this replacing it:

CFD_EnableSimulation = 1
CFD_ReinjectBody = 1
CFD_AirViscosity = 0.05
CFD_AirInCompressibility = 1
CFD_VoxelSizeScale = 1.0
CFD_VoxelNbVoxels = 20.0

These aren’t all the changes.

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I’ve just been looking over the flight_model files, and assuming my code is correct, the only plane I can find with CFD enabled is the 172 AS1000. I checked by eye the ones you mentioned, and they don’t have any CFD attributes listed.

$fm_files = Get-ChildItem -Recurse flight_model.cfg -Path 'D:\Flight Simulator\Official\OneStore\'
foreach ( $file in $fm_files) { $file | Select-String "CFD_EnableSimulation" }
asobo-aircraft-c172sp-as1000\SimObjects\Airplanes\Asobo_C172sp_AS1000\flight_model.cfg:141:CFD_EnableSimulation = 1

Just to confirm, I manually added the line “CFD_EnableSimulation = 1” into the “flight_model.cfg” file for the King Air, and re-ran the script:

foreach ( $file in $fm_files) { $file | Select-String "CFD_EnableSimulation" }
asobo-aircraft-c172sp-as1000\SimObjects\Airplanes\Asobo_C172sp_AS1000\flight_model.cfg:141:CFD_EnableSimulation = 1
asobo-aircraft-kingair350\SimObjects\Airplanes\Asobo_KingAir350\flight_model.cfg:149:CFD_EnableSimulation = 1

So I’m reasonably confident the 172 AS1000 is the only first party plane using CFD in my build of the sim, unless there is some other, hidden way to enable this.

Our BlackBox Trislander uses full CFD and Prop Physics

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:slight_smile:

I looked at that image, and wondered “How to I get to be a member of the Slander Club”. :rofl:

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Yesn’t :smiley: It’s a way more easy thing to implement and also you can activate CFD for any aircraft using dev mode by clicking one checkbox BUT tuning the CFD is hard for now as the SDK documentation does not provide information about the exact parameters to be used :slight_smile:

Current flight models use workarounds to be more realistic but these workarounds would basically be ignored by the CFD so some devs not yet move to the new flight model until they know what they can tune and how :wink:

Thanks for linking the New Propeller Simulation + CFD / Airplane list.

It’s impossible to keep track of every developer, so feel free to leave a comment there if an airplane is not listed or was just released with native prop and/or CFD simulation.

And yes, I also thought a lot more airplanes gonna get this feature since it sounded like a really good thing and easy to implement.

However just for example one statement from SimWorks Studio:

…there are still bugs in the implementation. But that is the lesser problem. We have prop drag, P-Factor and all these effects with the Kodiak & RV-14.

What if the prop physics are incorrect and we have to use weird values to get correct results? What if we only get right results in certain regimes but not everywhere?

If the “laws of physics” aren’t right, such problems will arise -so we want tuning options. This doesn’t give us any and we will wait until all quirks are ironed out.

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Just what I suspected. We are not quite there yet, but it’s a start ! :smiley:

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