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IDProjectCategoryView StatusLast Update
0001237OpenFOAMBugpublic2014-06-09 12:43
Reporteralbertop Assigned Tohenry  
Status closedResolutionfixed 
PlatformLinuxOSopenSUSEOS Version13.1
Summary0001237: Non negligible mass conservation error in twoPhaseEulerFoam
DescriptionThe twoPhaseEulerFoam solver shows a non negligible mass conservation error of the disperse phase.

Considering cases where there is no transport of disperse phase outside of the system, like a fluidized bed, the total volume of particles inside the system should be preserved. However, small errors are observed at each time step, which accumulate and lead to quite important mass loss or addition.
Steps To ReproduceThe problem can be reproduce using the 'fluidisedBed' tutorial.

In order to prevent particles from leaving the system, modify the boundary conditions so that alpha.particles is zero at the outlet. The particle velocity is already set to zero at the outlet in the tutorial. Note that this is not required to observe the problem, which happens also without this modification. The modified case is attached.

It can be observed that the error appears from the first time-step (see attached log). The following change in particle mass is observed in 2 seconds of simulation:

- Initial particle volume fraction: 2.75015
- Final particle volume fraction: 2.75553
- Total change in volume fraction: 0.00538 ==> 13.45 kg in 2 seconds

Considering the particle density is 2500 kg/m^3, this corresponds to a mass gain of 6.725 kg/s.

Additional Information- The problem happens with or without implicit treatment for the particle pressure.

- The error is limited (but not always removed) introducing multiple outer correctors (with relaxation of alpha if the bed is nearly packed), and using residual controls to ensure that the set of transport equations converges within certain tolerances (the tolerance for alpha has to be quite low). Reducing the time step has similar effects.
TagsNo tags attached.



2014-03-25 16:41


Tutorial.tar.gz (957,247 bytes)


2014-06-09 12:42

manager   ~0003117

Fixed in OpenFOAM-2.3.x

Issue History

Date Modified Username Field Change
2014-03-25 16:41 albertop New Issue
2014-03-25 16:41 albertop File Added: Tutorial.tar.gz
2014-06-09 12:42 henry Note Added: 0003117
2014-06-09 12:42 henry Status new => closed
2014-06-09 12:43 henry Assigned To => henry
2014-06-09 12:43 henry Resolution open => fixed