Oscillation in mesh refinement and unrefinement

kk415 · August 24, 2019, 08:17

Hello Foamers,

I am using dynamicMeshRefinement of OpenFoam and solving a static bubble test case. I am observing that a fix number of cell (i.e. 64) is getting refined and unrefined alternatively with the passage of time. Have anyone observed something like this before? What is the cause and remedy for this?

kk415 · August 31, 2019, 04:11

Hello Foamers,

I am attaching my output for your reference.

Courant Number mean: 1.69912e-07 max: 7.16164e-06
Interface Courant Number mean: 1.9221e-08 max: 6.04455e-06
Time = 0.09999

PIMPLE: iteration 1
Selected 112 cells for refinement out of 34896.
Refined from 34896 to 35680 cells.
Selected 0 split points out of a possible 1920.
Execution time for newMesh.update() = 0.44 s
Defining the group of the cells
MULES: Solving for alpha.water
Phase-1 volume fraction = 0.0316 Min(alpha.water) = 0 Max(alpha.water) = 1
solve the reinitialization equation
Interpolation of psi from coarser to finer mesh
Solve the modified reinitialization equation in finer mesh
Interpolation from finer to coarser mesh

Interpolation from finer to coarser mesh

Interpolation from finer to coarser mesh

MULES: Solving for alpha.water
DICPCG: Solving for p_rgh, Initial residual = 0.0100551, Final residual = 9.51849e-08, No Iterations 209
time step continuity errors : sum local = 2.11276e-14, global = -1.03739e-25, cumulative = 1.13937e-23
ExecutionTime = 115367 s ClockTime = 115435 s

Courant Number mean: 1.70292e-07 max: 7.16211e-06
Interface Courant Number mean: 1.92162e-08 max: 6.04469e-06
Time = 0.099995

PIMPLE: iteration 1
Selected 0 cells for refinement out of 35680.
Selected 112 split points out of a possible 1920.
Unrefined from 35680 to 34896 cells.
Execution time for newMesh.update() = 0.4 s
Defining the group of the cells
MULES: Solving for alpha.water
Phase-1 volume fraction = 0.0316 Min(alpha.water) = 0 Max(alpha.water) = 1
solve the reinitialization equation
Interpolation of psi from coarser to finer mesh
Solve the modified reinitialization equation in finer mesh
Interpolation from finer to coarser mesh

Interpolation from finer to coarser mesh

Interpolation from finer to coarser mesh

MULES: Solving for alpha.water
DICPCG: Solving for p_rgh, Initial residual = 0.0100496, Final residual = 9.16363e-08, No Iterations 220
time step continuity errors : sum local = 2.02673e-14, global = -3.25376e-25, cumulative = 1.10683e-23
ExecutionTime = 115375 s ClockTime = 115443 s

Courant Number mean: 1.69908e-07 max: 7.16148e-06
Interface Courant Number mean: 1.92202e-08 max: 6.04428e-06
Time = 0.1

PIMPLE: iteration 1
Selected 112 cells for refinement out of 34896.
Refined from 34896 to 35680 cells.
Selected 0 split points out of a possible 1920.
Execution time for newMesh.update() = 0.43 s
Defining the group of the cells
MULES: Solving for alpha.water
Phase-1 volume fraction = 0.0316 Min(alpha.water) = 0 Max(alpha.water) = 1
solve the reinitialization equation
Interpolation of psi from coarser to finer mesh
Solve the modified reinitialization equation in finer mesh
Interpolation from finer to coarser mesh

Interpolation from finer to coarser mesh

Interpolation from finer to coarser mesh

MULES: Solving for alpha.water
DICPCG: Solving for p_rgh, Initial residual = 0.0100549, Final residual = 9.61359e-08, No Iterations 209
time step continuity errors : sum local = 2.13378e-14, global = -1.83658e-25, cumulative = 1.08847e-23
ExecutionTime = 115383 s ClockTime = 115451 s

This problem is increasing my computational time and I am losing the advantage of AMR.

August 24, 2019, 08:17	Oscillation in adaptive mesh refinement	#1
kk415 Senior Member krishna kant Join Date: Feb 2016 Location: Hyderabad, India Posts: 133 Rep Power: 10	Hello Foamers, I am using dynamicMeshRefinement of OpenFoam and solving a static bubble test case. I am observing that a fix number of cell (i.e. 64) is getting refined and unrefined alternatively with the passage of time. Have anyone observed something like this before? What is the cause and remedy for this? Last edited by kk415; August 31, 2019 at 04:06.

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August 31, 2019, 04:11		#2
kk415 Senior Member krishna kant Join Date: Feb 2016 Location: Hyderabad, India Posts: 133 Rep Power: 10	Hello Foamers, I am attaching my output for your reference. Courant Number mean: 1.69912e-07 max: 7.16164e-06 Interface Courant Number mean: 1.9221e-08 max: 6.04455e-06 Time = 0.09999 PIMPLE: iteration 1 Selected 112 cells for refinement out of 34896. Refined from 34896 to 35680 cells. Selected 0 split points out of a possible 1920. Execution time for newMesh.update() = 0.44 s Defining the group of the cells MULES: Solving for alpha.water Phase-1 volume fraction = 0.0316 Min(alpha.water) = 0 Max(alpha.water) = 1 solve the reinitialization equation Interpolation of psi from coarser to finer mesh Solve the modified reinitialization equation in finer mesh Interpolation from finer to coarser mesh Interpolation from finer to coarser mesh Interpolation from finer to coarser mesh MULES: Solving for alpha.water DICPCG: Solving for p_rgh, Initial residual = 0.0100551, Final residual = 9.51849e-08, No Iterations 209 time step continuity errors : sum local = 2.11276e-14, global = -1.03739e-25, cumulative = 1.13937e-23 ExecutionTime = 115367 s ClockTime = 115435 s Courant Number mean: 1.70292e-07 max: 7.16211e-06 Interface Courant Number mean: 1.92162e-08 max: 6.04469e-06 Time = 0.099995 PIMPLE: iteration 1 Selected 0 cells for refinement out of 35680. Selected 112 split points out of a possible 1920. Unrefined from 35680 to 34896 cells. Execution time for newMesh.update() = 0.4 s Defining the group of the cells MULES: Solving for alpha.water Phase-1 volume fraction = 0.0316 Min(alpha.water) = 0 Max(alpha.water) = 1 solve the reinitialization equation Interpolation of psi from coarser to finer mesh Solve the modified reinitialization equation in finer mesh Interpolation from finer to coarser mesh Interpolation from finer to coarser mesh Interpolation from finer to coarser mesh MULES: Solving for alpha.water DICPCG: Solving for p_rgh, Initial residual = 0.0100496, Final residual = 9.16363e-08, No Iterations 220 time step continuity errors : sum local = 2.02673e-14, global = -3.25376e-25, cumulative = 1.10683e-23 ExecutionTime = 115375 s ClockTime = 115443 s Courant Number mean: 1.69908e-07 max: 7.16148e-06 Interface Courant Number mean: 1.92202e-08 max: 6.04428e-06 Time = 0.1 PIMPLE: iteration 1 Selected 112 cells for refinement out of 34896. Refined from 34896 to 35680 cells. Selected 0 split points out of a possible 1920. Execution time for newMesh.update() = 0.43 s Defining the group of the cells MULES: Solving for alpha.water Phase-1 volume fraction = 0.0316 Min(alpha.water) = 0 Max(alpha.water) = 1 solve the reinitialization equation Interpolation of psi from coarser to finer mesh Solve the modified reinitialization equation in finer mesh Interpolation from finer to coarser mesh Interpolation from finer to coarser mesh Interpolation from finer to coarser mesh MULES: Solving for alpha.water DICPCG: Solving for p_rgh, Initial residual = 0.0100549, Final residual = 9.61359e-08, No Iterations 209 time step continuity errors : sum local = 2.13378e-14, global = -1.83658e-25, cumulative = 1.08847e-23 ExecutionTime = 115383 s ClockTime = 115451 s This problem is increasing my computational time and I am losing the advantage of AMR.