time step continuity error

Submitted by VAJIHEH on Thu, 12/08/2011 - 16:03

Hi Everyone,

I am running the settlingtestMPI example, where I get this error of time step continuity. I would appreciate any advise.

Time = 0.15

Courant Number mean: 5.34588e-05 max: 0.00517684

- evolve()

Starting up LIGGGHTS

Executing command: 'run 100 '

run 100 Setting up run ...

Memory usage per processor = 3.04352 Mbytes

Step Atoms KinEng 1 Volume

14901 1 0 5.1835199e-17 0.001

15000 1 0 5.1835199e-17 0.001

15001 1 0 5.1835199e-17 0.001

Loop time of 0.00144196 on 2 procs for 100 steps with 1 atoms

Pair time (%) = 0.000131488 (9.11872)

Neigh time (%) = 3.57628e-06 (0.248016)

Comm time (%) = 0.000307798 (21.3459)

Outpt time (%) = 6.60419e-05 (4.58003)

Other time (%) = 0.000933051 (64.7073)

Nlocal: 0.5 ave 1 max 0 min

Histogram: 1 0 0 0 0 0 0 0 0 1

Nghost: 0 ave 0 max 0 min

Histogram: 2 0 0 0 0 0 0 0 0 0

Neighs: 0 ave 0 max 0 min

Histogram: 2 0 0 0 0 0 0 0 0 0

Total # of neighbors = 0

Ave neighs/atom = 0

Neighbor list builds = 1

Dangerous builds = 0

LIGGGHTS finished

timeStepFraction() = 1

evolve done

update Ksl.internalField()

totaldragforceEuler calculus

totaldragforceEuler = 0

dv/dt =sum(ddt(voidfraction)) [0 0 -1 0 0 0 0] 0

DILUPBiCG: Solving for Ux, Initial residual = 0.00904063, Final residual = 3.06866e-07, No Iterations 2

DILUPBiCG: Solving for Uy, Initial residual = 0.00923653, Final residual = 2.24192e-07, No Iterations 2

DILUPBiCG: Solving for Uz, Initial residual = 0.00522867, Final residual = 2.68063e-07, No Iterations 2

DICPCG: Solving for p, Initial residual = 0.0273475, Final residual = 0.00207778, No Iterations 4

time step continuity errors : sum local = 8.04045e-07, global = 1.33621e-08, cumulative = 1.31908e-05

DICPCG: Solving for p, Initial residual = 0.00218924, Final residual = 0.000168388, No Iterations 54

time step continuity errors : sum local = 8.04385e-07, global = 1.33633e-08, cumulative = 1.32041e-05

DICPCG: Solving for p, Initial residual = 0.000209225, Final residual = 1.83151e-05, No Iterations 55

time step continuity errors : sum local = 8.04424e-07, global = 1.34587e-08, cumulative = 1.32176e-05

ExecutionTime = 6.38 s ClockTime = 6 s

End

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VAJIHEH | Fri, 12/09/2011 - 21:18

Thanks for the help Chris,

I have another question regarding the bounding box which i define in in.liggghts_init. I belive these are the walls of the geometry for DEM calculations? how can I change this box to be similar to my CFD geometry walls?

Regards,
Vajiiheh

cgoniva's picture

cgoniva | Mon, 12/12/2011 - 12:16

Hi!

defining a bounding box does not automatically make it a wall for the particles, you have to specify the walls by a seperate command (e.g. xwalls, ywalls etc.).
Please see the in.liggghts_init file in the tutorials.

you can specify the size of the bounding box by defining minimal and maximal x,y,z values.

You find info on that in the LIGGGHTS documentation.

Cheers,
Chris