Cannot run the code properly: very large time step continuity error

crst15 · January 17, 2014, 04:40

Hi all,

I am still very new to OpenFOAM. Currently I'm using OpenFOAM 2.2.2 and I've finished doing all of the tutorials given in the user guide. I want to model a basic data center configuration. My supervisor recommended me to base my model on the "hotRoom" tutorial using buoyantBoussinesqSimpleFoam as the solver.

Initially, I had been able to run the simulation smoothly using just natural convection. Now, I incorporate some cool air raised from the floor in order to introduce forced convection cooling to the room. I met no problem when generating the mesh, but I got problems when I run the code. I have tried to fix it a lot of times, but still end up with the same error messages as follow.

Code:

Time = 6

DILUPBiCG:  Solving for Ux, Initial residual = 0.192382, Final residual = 0.00139781, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.328512, Final residual = 0.00357734, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.281499, Final residual = 0.00392744, No Iterations 1
DILUPBiCG:  Solving for T, Initial residual = 0.000289576, Final residual = 6.58994e-06, No Iterations 1
DICPCG:  Solving for p_rgh, Initial residual = 0.999852, Final residual = 27153.3, No Iterations 1001
time step continuity errors : sum local = 1.90649e+33, global = 4.30234e+27, cumulative = 4.30429e+27
DILUPBiCG:  Solving for epsilon, Initial residual = 0.0588009, Final residual = 2.80475e-06, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 0.086828, Final residual = 0.00649997, No Iterations 1
ExecutionTime = 62.06 s  ClockTime = 64 s

Time = 7

DILUPBiCG:  Solving for Ux, Initial residual = 0.000934178, Final residual = 7.98045e-06, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.00368795, Final residual = 5.94455e-05, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.00220201, Final residual = 1.0352e-05, No Iterations 1
DILUPBiCG:  Solving for T, Initial residual = 0.318863, Final residual = 0.0149065, No Iterations 1
DICPCG:  Solving for p_rgh, Initial residual = 1, Final residual = 0.0094375, No Iterations 19
time step continuity errors : sum local = 2.49073e+89, global = 3.75377e+88, cumulative = 3.75377e+88
#0  Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#1  Foam::sigFpe::sigHandler(int) in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#2  Uninterpreted: 
#3  Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#4  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libfiniteVolume.so"
#5  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam222/platforms/linuxGccDPOpt/bin/buoyantBoussinesqSimpleFoam"
#6  Foam::fvMatrix<double>::solve() in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so"
#7  Foam::incompressible::RASModels::kEpsilon::correct() in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so"
#8  
 in "/opt/openfoam222/platforms/linuxGccDPOpt/bin/buoyantBoussinesqSimpleFoam"
#9  __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#10  
 in "/opt/openfoam222/platforms/linuxGccDPOpt/bin/buoyantBoussinesqSimpleFoam"
Floating point exception (core dumped)

I have no idea on what is going on. One thing I notice is the very very huge time step continuity errors, and I know that there must be something wrong in my code. However, I have no more idea on how to fix this problem.

Could anybody please help me?? I have attached several files which I think are the main cause of the error.

Kind regards,

Steven

epsilon.txt

k.txt

p_rgh.txt

U.txt

fvSolution.txt

crst15 · January 17, 2014, 05:22

I forgot to clear all of the comments I put inside the files I've attached.
My apologize for that. Just ignore them

.

Cheers

akidess · January 17, 2014, 05:35

Do your inlets and outlets allow for the same mass flow? I.e. are you putting in the same flux as you are taking out?

crst15 · January 17, 2014, 07:45

Hi Anton,

Thanks for your reply. Yes, I have employed mass continuity equation for the air velocity at inlets and outlets. I set the inlets and outlets to a particular temperature, so that I can determine the density variation and hence the velocity for each of them (the area for inlets and outlets are equal in magnitude). However, I rounded up the value up to 4 significant figures. Does it affect the result and causing error?

Cheers

Himanshu_kpr · February 19, 2014, 09:07

Quote:

Originally Posted by crst15

Hi all,

Code:

Time = 6

DILUPBiCG:  Solving for Ux, Initial residual = 0.192382, Final residual = 0.00139781, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.328512, Final residual = 0.00357734, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.281499, Final residual = 0.00392744, No Iterations 1
DILUPBiCG:  Solving for T, Initial residual = 0.000289576, Final residual = 6.58994e-06, No Iterations 1
DICPCG:  Solving for p_rgh, Initial residual = 0.999852, Final residual = 27153.3, No Iterations 1001
time step continuity errors : sum local = 1.90649e+33, global = 4.30234e+27, cumulative = 4.30429e+27
DILUPBiCG:  Solving for epsilon, Initial residual = 0.0588009, Final residual = 2.80475e-06, No Iterations 1
DILUPBiCG:  Solving for k, Initial residual = 0.086828, Final residual = 0.00649997, No Iterations 1
ExecutionTime = 62.06 s  ClockTime = 64 s

Time = 7

DILUPBiCG:  Solving for Ux, Initial residual = 0.000934178, Final residual = 7.98045e-06, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.00368795, Final residual = 5.94455e-05, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 0.00220201, Final residual = 1.0352e-05, No Iterations 1
DILUPBiCG:  Solving for T, Initial residual = 0.318863, Final residual = 0.0149065, No Iterations 1
DICPCG:  Solving for p_rgh, Initial residual = 1, Final residual = 0.0094375, No Iterations 19
time step continuity errors : sum local = 2.49073e+89, global = 3.75377e+88, cumulative = 3.75377e+88
#0  Foam::error::printStack(Foam::Ostream&) in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#1  Foam::sigFpe::sigHandler(int) in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#2  Uninterpreted: 
#3  Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#4  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libfiniteVolume.so"
#5  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/openfoam222/platforms/linuxGccDPOpt/bin/buoyantBoussinesqSimpleFoam"
#6  Foam::fvMatrix<double>::solve() in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so"
#7  Foam::incompressible::RASModels::kEpsilon::correct() in "/opt/openfoam222/platforms/linuxGccDPOpt/lib/libincompressibleRASModels.so"
#8  
 in "/opt/openfoam222/platforms/linuxGccDPOpt/bin/buoyantBoussinesqSimpleFoam"
#9  __libc_start_main in "/lib/i386-linux-gnu/libc.so.6"
#10  
 in "/opt/openfoam222/platforms/linuxGccDPOpt/bin/buoyantBoussinesqSimpleFoam"
Floating point exception (core dumped)

I have no idea on what is going on. One thing I notice is the very very huge time step continuity errors, and I know that there must be something wrong in my code. However, I have no more idea on how to fix this problem.

Could anybody please help me?? I have attached several files which I think are the main cause of the error.

Kind regards,

Steven

Hi Steven ,

Did you manage to get a solution to your problem of high time step errors, I am also facing the same errors.

Code:

Time = 1

smoothSolver:  Solving for Ux, Initial residual = 1, Final residual = 0.0422091, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 0.030476, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 1, Final residual = 0.0306028, No Iterations 2
DICPCG:  Solving for p, Initial residual = 1, Final residual = 0.134351, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.691177, Final residual = 0.0125443, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.055563, Final residual = 0.00557511, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0220327, Final residual = 0.00114917, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0159711, Final residual = 0.00917452, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0187368, Final residual = 0.00188332, No Iterations 100
time step continuity errors : sum local = 1.54575, global = 0.135485, cumulative = 0.135485
ExecutionTime = 46.8 s  ClockTime = 47 s

Time = 2

smoothSolver:  Solving for Ux, Initial residual = 0.451668, Final residual = 0.028682, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.751694, Final residual = 0.0484893, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.714429, Final residual = 0.0431807, No Iterations 2
DICPCG:  Solving for p, Initial residual = 0.22116, Final residual = 0.00557813, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.249683, Final residual = 0.00707944, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0734626, Final residual = 0.00226722, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.024608, Final residual = 0.00154313, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0104501, Final residual = 0.00039303, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.00496492, Final residual = 0.000300146, No Iterations 100
time step continuity errors : sum local = 0.075618, global = -0.00192783, cumulative = 0.133557
ExecutionTime = 82.56 s  ClockTime = 83 s

Time = 3

smoothSolver:  Solving for Ux, Initial residual = 0.193993, Final residual = 0.0125072, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.292282, Final residual = 0.0178138, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.248495, Final residual = 0.0144195, No Iterations 2
DICPCG:  Solving for p, Initial residual = 0.257503, Final residual = 0.00678077, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.364373, Final residual = 0.00410846, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.072356, Final residual = 0.00315433, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0276443, Final residual = 0.00105369, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0124894, Final residual = 0.000895709, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.00933875, Final residual = 0.000367333, No Iterations 100
time step continuity errors : sum local = 0.121702, global = 0.0140299, cumulative = 0.147587
ExecutionTime = 118.29 s  ClockTime = 118 s

Time = 4

smoothSolver:  Solving for Ux, Initial residual = 0.12122, Final residual = 0.00895779, No Iterations 2
smoothSolver:  Solving for Uy, Initial residual = 0.141129, Final residual = 0.00892482, No Iterations 2
smoothSolver:  Solving for Uz, Initial residual = 0.119265, Final residual = 0.00762635, No Iterations 2
DICPCG:  Solving for p, Initial residual = 0.256797, Final residual = 0.00561705, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.135723, Final residual = 0.000590494, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.0450871, Final residual = 0.00114046, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.00622627, Final residual = 0.000147822, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.00502869, Final residual = 6.77996e-05, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.00374468, Final residual = 3.62683e-05, No Iterations 100
time step continuity errors : sum local = 0.210205, global = 0.0591626, cumulative = 0.20675
ExecutionTime = 153.99 s  ClockTime = 154 s

Time = 5

smoothSolver:  Solving for Ux, Initial residual = 0.269691, Final residual = 0.00476426, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.254113, Final residual = 0.00455208, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.25261, Final residual = 0.00443524, No Iterations 4
DICPCG:  Solving for p, Initial residual = 0.0143989, Final residual = 0.000155821, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.000232032, Final residual = 6.96373e-07, No Iterations 100
DICPCG:  Solving for p, Initial residual = 0.00017752, Final residual = 1.75389e-06, No Iterations 100
DICPCG:  Solving for p, Initial residual = 7.55826e-05, Final residual = 6.34178e-07, No Iterations 100
DICPCG:  Solving for p, Initial residual = 8.81612e-05, Final residual = 8.39305e-07, No Iterations 100
DICPCG:  Solving for p, Initial residual = 7.70637e-05, Final residual = 7.11628e-07, No Iterations 100
time step continuity errors : sum local = 2.85601, global = 0.77367, cumulative = 0.980419
ExecutionTime = 190.23 s  ClockTime = 190 s

Time = 6

smoothSolver:  Solving for Ux, Initial residual = 0.29682, Final residual = 0.00460685, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.293445, Final residual = 0.00429992, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.299224, Final residual = 0.00440848, No Iterations 4
DICPCG:  Solving for p, Initial residual = 9.35095e-05, Final residual = 1.09954e-06, No Iterations 100
DICPCG:  Solving for p, Initial residual = 4.91151e-06, Final residual = 4.30099e-08, No Iterations 100
DICPCG:  Solving for p, Initial residual = 8.06364e-06, Final residual = 1.08889e-07, No Iterations 100
DICPCG:  Solving for p, Initial residual = 4.85845e-06, Final residual = 6.03338e-08, No Iterations 100
DICPCG:  Solving for p, Initial residual = 5.74193e-06, Final residual = 7.29363e-08, No Iterations 100
DICPCG:  Solving for p, Initial residual = 5.16892e-06, Final residual = 6.34448e-08, No Iterations 100
time step continuity errors : sum local = 77.6375, global = 23.7415, cumulative = 24.7219
ExecutionTime = 226.48 s  ClockTime = 227 s

Time = 7

smoothSolver:  Solving for Ux, Initial residual = 0.318025, Final residual = 0.00485944, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.319293, Final residual = 0.00491225, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.321538, Final residual = 0.0049102, No Iterations 4
DICPCG:  Solving for p, Initial residual = 5.87032e-06, Final residual = 6.7756e-08, No Iterations 100
DICPCG:  Solving for p, Initial residual = 2.36787e-07, Final residual = 1.64937e-09, No Iterations 100
DICPCG:  Solving for p, Initial residual = 4.45469e-07, Final residual = 4.81168e-09, No Iterations 100
DICPCG:  Solving for p, Initial residual = 2.28813e-07, Final residual = 2.19573e-09, No Iterations 100
DICPCG:  Solving for p, Initial residual = 2.69278e-07, Final residual = 2.80125e-09, No Iterations 100
DICPCG:  Solving for p, Initial residual = 2.37724e-07, Final residual = 2.25178e-09, No Iterations 100
time step continuity errors : sum local = 1284.9, global = 278.963, cumulative = 303.685
ExecutionTime = 262.78 s  ClockTime = 263 s

Time = 8

smoothSolver:  Solving for Ux, Initial residual = 0.311316, Final residual = 0.00514459, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.315939, Final residual = 0.00511636, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.320675, Final residual = 0.00517196, No Iterations 4
DICPCG:  Solving for p, Initial residual = 3.33222e-07, Final residual = 6.01642e-09, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.04966e-08, Final residual = 2.08452e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.98828e-08, Final residual = 5.56181e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.1944e-08, Final residual = 3.33406e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.39477e-08, Final residual = 3.59735e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.24737e-08, Final residual = 2.85011e-10, No Iterations 100
time step continuity errors : sum local = 67282.6, global = 12498.2, cumulative = 12801.9
ExecutionTime = 298.53 s  ClockTime = 299 s

Time = 9

smoothSolver:  Solving for Ux, Initial residual = 0.321623, Final residual = 0.00491377, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.324749, Final residual = 0.00493128, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.328151, Final residual = 0.0049728, No Iterations 4
DICPCG:  Solving for p, Initial residual = 1.74395e-08, Final residual = 1.91872e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 6.3535e-10, Final residual = 5.90779e-12, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.16615e-09, Final residual = 1.47742e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 5.85987e-10, Final residual = 7.23812e-12, No Iterations 100
DICPCG:  Solving for p, Initial residual = 6.90344e-10, Final residual = 1.02724e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 6.25039e-10, Final residual = 8.83031e-12, No Iterations 100
time step continuity errors : sum local = 953861, global = 176059, cumulative = 188861
ExecutionTime = 335.09 s  ClockTime = 336 s

Time = 10

smoothSolver:  Solving for Ux, Initial residual = 0.314423, Final residual = 0.00535151, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.319104, Final residual = 0.00540234, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.324228, Final residual = 0.00544633, No Iterations 4
DICPCG:  Solving for p, Initial residual = 1.42342e-08, Final residual = 2.40163e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 3.85046e-10, Final residual = 9.44379e-12, No Iterations 100
DICPCG:  Solving for p, Initial residual = 7.06354e-10, Final residual = 2.04228e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 4.03936e-10, Final residual = 1.17704e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 4.79926e-10, Final residual = 1.53423e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 4.42188e-10, Final residual = 1.16098e-11, No Iterations 100
time step continuity errors : sum local = 4.0144e+07, global = 5.41432e+06, cumulative = 5.60318e+06
ExecutionTime = 371.52 s  ClockTime = 372 s

Time = 11

smoothSolver:  Solving for Ux, Initial residual = 0.317013, Final residual = 0.00480118, No Iterations 4
smoothSolver:  Solving for Uy, Initial residual = 0.320907, Final residual = 0.00484383, No Iterations 4
smoothSolver:  Solving for Uz, Initial residual = 0.324356, Final residual = 0.00487736, No Iterations 4
DICPCG:  Solving for p, Initial residual = 3.42875e-08, Final residual = 4.90087e-10, No Iterations 100
DICPCG:  Solving for p, Initial residual = 9.60001e-10, Final residual = 1.46431e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 2.01496e-09, Final residual = 5.44019e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.05359e-09, Final residual = 1.75239e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.24825e-09, Final residual = 2.67017e-11, No Iterations 100
DICPCG:  Solving for p, Initial residual = 1.14462e-09, Final residual = 2.11082e-11, No Iterations 100
time step continuity errors : sum local = 6.98003e+08, global = 1.12935e+08, cumulative = 1.18538e+08
ExecutionTime = 407.69 s  ClockTime = 408 s

crst15 · February 21, 2014, 03:35

Hi Himanshu,

Yes, finally I was able to solve the problem. If I'm not mistaken, I either put wrong boundary conditions or several boundary conditions did not suit well to the case I was simulating. However, Anton's suggestion about mass continuity also plays important role to make sure small continuity error.

What are you simulating? Maybe just put more detail about your case since it's hard to guess what's going on just from your post.

Cheers

afrotimy · February 21, 2014, 20:49

Recalculate your time step with ref to Courant number, speed and the cell size.

You should be fine. Chose the mesh size based on max U and minimum cell size or vise versa.

crst15 · February 21, 2014, 21:09

And also make sure your meshes are ok. Try to type "checkmesh" in command window and see the results. Last time I got problem because some of my meshes were not properly generated.

afrotimy · December 12, 2014, 09:16

Also ensure uniform mesh near the movingWall. Grading of 1 in an interior domain created near the wall. Others can be graded.

afrotimy · December 14, 2014, 18:17

Use laplaceFaceDecomposition in you dynamicMesh solver with motionU.

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January 17, 2014, 05:22	apologize	#2
crst15 New Member Steven Join Date: Dec 2013 Location: Perth Posts: 15 Rep Power: 12	I forgot to clear all of the comments I put inside the files I've attached. My apologize for that. Just ignore them . Cheers

January 17, 2014, 05:35		#3
akidess Senior Member Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,377 Rep Power: 29	Do your inlets and outlets allow for the same mass flow? I.e. are you putting in the same flux as you are taking out? __________________ On twitter @akidTwit Spend as much time formulating your questions as you expect people to spend on their answer.

January 17, 2014, 07:45		#4
crst15 New Member Steven Join Date: Dec 2013 Location: Perth Posts: 15 Rep Power: 12	Hi Anton, Thanks for your reply. Yes, I have employed mass continuity equation for the air velocity at inlets and outlets. I set the inlets and outlets to a particular temperature, so that I can determine the density variation and hence the velocity for each of them (the area for inlets and outlets are equal in magnitude). However, I rounded up the value up to 4 significant figures. Does it affect the result and causing error? Cheers

February 21, 2014, 03:35		#6
crst15 New Member Steven Join Date: Dec 2013 Location: Perth Posts: 15 Rep Power: 12	Hi Himanshu, Yes, finally I was able to solve the problem. If I'm not mistaken, I either put wrong boundary conditions or several boundary conditions did not suit well to the case I was simulating. However, Anton's suggestion about mass continuity also plays important role to make sure small continuity error. What are you simulating? Maybe just put more detail about your case since it's hard to guess what's going on just from your post. Cheers

February 21, 2014, 20:49		#7
afrotimy Member Francis Join Date: Jan 2014 Location: Toronto Posts: 50 Rep Power: 12	Recalculate your time step with ref to Courant number, speed and the cell size. You should be fine. Chose the mesh size based on max U and minimum cell size or vise versa. pici likes this. Last edited by wyldckat; February 22, 2014 at 05:13. Reason: merged two posts, since they were posted 1 minute apart

February 21, 2014, 21:09		#8
crst15 New Member Steven Join Date: Dec 2013 Location: Perth Posts: 15 Rep Power: 12	And also make sure your meshes are ok. Try to type "checkmesh" in command window and see the results. Last time I got problem because some of my meshes were not properly generated.

December 12, 2014, 09:16		#9
afrotimy Member Francis Join Date: Jan 2014 Location: Toronto Posts: 50 Rep Power: 12	Also ensure uniform mesh near the movingWall. Grading of 1 in an interior domain created near the wall. Others can be graded.

December 14, 2014, 18:17		#10
afrotimy Member Francis Join Date: Jan 2014 Location: Toronto Posts: 50 Rep Power: 12	Use laplaceFaceDecomposition in you dynamicMesh solver with motionU.