Help with a problem running MPPICFoam
 

Hi,

I am looking for some help troubleshooting a problem that I have when running MPPICFOam.

I first started with the cyclone tutorial and then changed the geometry/mesh to a simplified version of my solution, I also ran it with lower then actual boundary conditions. This ran with a small problem that the was easy to correct by adding adjustable time steps with a max Courant number.
The problem was that the k.air would become unstable.
bounding k.air, min: -1.27685e+10 max: 5.48249e+12 average: 6.19542e+10
And the time step would become really small.
Courant Number mean: 0.000995892 max: 0.994049
deltaT = 3.76105e-10
Time = 1.01671
I solved this by decrease the max courant number.

Thinking I solved the problem I ran a full scale simulation. I ran into some problems here as well.
The first on was the:
Cloud: kinematicCloud injector: model1
Added 1000 new parcels

GAMG: Solving for kinematicCloud:alpha, Initial residual = 0.973777, Final residual = 2.56743e-16, No Iterations 1

I solved this by changing the Courant number as well.

Having run that simulation I changed the geometry a little to see what the effect will be on the particle cloud. Now the simulation doesn't work with the setting of the previous simulation.
It seems that the cell volume fraction goes over one and the simulation crashes.

This is the final time step from the log:
Courant Number mean: 0.0334176 max: 1.68594
deltaT = 0.0001
Time = 1.1791

Evolving kinematicCloud

Solving 3-D cloud kinematicCloud

Cloud: kinematicCloud injector: model1
Added 500 new parcels

GAMG: Solving for kinematicCloud:alpha, Initial residual = 3.97258e-07, Final residual = 3.97258e-07, No Iterations 0
Cloud: kinematicCloud
Current number of parcels = 895500
Current mass in system = 14.925
Linear momentum = (-46.7636 1.19096 -129.692)
|Linear momentum| = 137.871
Linear kinetic energy = 693.699
Average particle per parcel = 15962.1
Injector model1:
- parcels added = 895500
- mass introduced = 14.925
Parcel fate: system (number, mass)
- escape = 0, 0
Parcel fate: patch walls (number, mass)
- escape = 0, 0
- stick = 0, 0
Parcel fate: patch inlet (number, mass)
- escape = 0, 0
- stick = 0, 0
Parcel fate: patch outletLeft (number, mass)
- escape = 0, 0
- stick = 0, 0
Parcel fate: patch outletRight (number, mass)
- escape = 0, 0
- stick = 0, 0
Parcel fate: patch mealInlet (number, mass)
- escape = 0, 0
- stick = 0, 0
Min cell volume fraction = 0
Max cell volume fraction = 1.13689
Min dense number of parcels = 3.00998

PIMPLE: iteration 1
smoothSolver: Solving for U.airx, Initial residual = 0.000278857, Final residual = 3.31328e-07, No Iterations 1
smoothSolver: Solving for U.airy, Initial residual = 0.000180067, Final residual = 2.27856e-07, No Iterations 1
smoothSolver: Solving for U.airz, Initial residual = 0.000107174, Final residual = 1.14479e-07, No Iterations 1
GAMG: Solving for p, Initial residual = 0.143885, Final residual = 0.00120846, No Iterations 2
time step continuity errors : sum local = 4.15175e-08, global = 1.38267e-10, cumulative = 1.45161e-08
GAMG: Solving for p, Initial residual = 0.00607239, Final residual = 9.60646e-07, No Iterations 12
time step continuity errors : sum local = 3.29827e-11, global = 1.07283e-12, cumulative = 1.45172e-08
smoothSolver: Solving for k.air, Initial residual = 9.97073e-05, Final residual = 1.01603e-07, No Iterations 1
bounding k.air, min: -1.53681 max: 263.462 average: 2.57929
ExecutionTime = 46203.4 s ClockTime = 47319 s

Courant Number mean: 0.0334176 max: 2.09401
deltaT = 0.0001
Time = 1.1792

Evolving kinematicCloud

Solving 3-D cloud kinematicCloud

Cloud: kinematicCloud injector: model1
Added 500 new parcels

GAMG: Solving for kinematicCloud:alpha, Initial residual = 0.694129, Final residual = 3.6204e-17, No Iterations 1


I have tried changing the fineness of the mesh, as well as the time step size and it still doesn't want to run. It also crashes at the same time in the simulation, it doesn't matter what I do to the time step or mesh size.

If anyone has a suggestion on what I should look at to try and fix this problem it will be very helpful.

Thanks,

Hi,

I solved the problem by increasing my parcelsPerSecond by 50%. I think there was an issue with the parcel size and the cell size that might have been causing the cell volume fraction to go over 1.0 and cause it to crash.