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IDProjectCategoryView StatusLast Update
0002875OpenFOAM[All Projects] Bugpublic2018-03-12 14:01
ReporterJessAssigned Tohenry 
PrioritynormalSeveritymajorReproducibilityhave not tried
Status closedResolutionno change required 
PlatformLinuxOSUbuntuOS Version16.04
Product Version4.1 
Fixed in Version 
Summary0002875: Difference parallel and serial running
DescriptionCase description: Air blowing into an open space with only a small wall section. Turbulence model used: RNG kEpsilon

Problem : When running the exact same case using various methods of decomposition for parallel run on one to 8 processors, the number of iterations before convergence (steady state case) varies greatly (from 245 to 1252), as does one value extracted from each end result (TKE varies from 0.255 to 1.198).

Similar results are obtained for OpenFoam 2.4.

Laminar case was tried for same geometry and initial and boundary conditions with less extreme differences between various decompositions. (though the differences exist)

Issue #0000747 was consulted at https://bugs.openfoam.org/view.php?id=747
describing a similar problem, where it is said to have been resolved, which doesn't seem to be the case?

Steps To ReproduceUse uploaded compressed folder containing DecomposePar dictionary for Scotch decomposition into 4 processors.
decomposePar
mpirun -np 4 simpleFoam -parallel > log &
reconstructPar
postProcess -func sampleDict

Look at value k at position (-0.3 6 0) in the last iteration folder in postprocessing folder.

Repeat same actions varying each time the processor decomposition. Results obtained in table below.
Additional InformationDecompositions tried out Number of iterations before convergence Key value (k at position (-0.3 6 0)
Simple: 8 (2 2 2) 785 0.711
Scotch: 8 291 0.354
Scotch: 2 375 0.556
Simple: 8 (1 8 1) 348 0.564
Simple: 2 (1 2 1) 513 1.17
Simple:4 (2 1 2) 266 1.15
Scotch: 4 245 0.255
Simple: 8 (4 1 2) 1252 1.198
No Split up (1 processor) 380 0.57
TagsNo tags attached.

Activities

Jess

2018-03-12 13:54

reporter  

simpleductred.zip (2,244,623 bytes)

henry

2018-03-12 14:01

manager   ~0009414

We would classify this as user support which would need finance to work on for you.

Issue History

Date Modified Username Field Change
2018-03-12 13:54 Jess New Issue
2018-03-12 13:54 Jess File Added: simpleductred.zip
2018-03-12 14:01 henry Assigned To => henry
2018-03-12 14:01 henry Status new => closed
2018-03-12 14:01 henry Resolution open => no change required
2018-03-12 14:01 henry Note Added: 0009414