View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000356 | OpenFOAM | Bug | public | 2011-12-14 11:04 | 2011-12-29 14:44 |
| Reporter | niklas.wikstrom | Assigned To | henry | ||
| Priority | normal | Severity | crash | Reproducibility | always |
| Status | closed | Resolution | fixed | ||
| Platform | Dell Intel X557 | OS | RHEL | OS Version | 5.4 |
| Summary | 0000356: interFoam results depend on geometrical translation of domain | ||||
| Description | git sha 4a2c44da8bc08afd6ccaf7a1b2106103748ec436 Possibly a well known issue with the p_rgh formulation but maby worth to mention anyway: The interFoam solution is dependent on the spatial location of the domain. | ||||
| Steps To Reproduce | run interFoam tutorial "damBreak" transformPoints -translate "(0 1000 0)" rerun interFoam tutorial "damBreak" --> Crash/Different result | ||||
| Additional Information | Thank you all and Merry Christmas! | ||||
| Tags | interFoam, multiphase | ||||
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Uhm... a few questions: 1. Did you translate before or after running "setFields"? If it was before setFields, then the dam domain is empty! 2. 1000 over Y axis... I can't remember over which axis gravity works on this tutorial case... but if it is Y, perhaps it takes into account the altitude as well!? Disclaimer: I'm not 100% familiar with the intrinsics of interFoam :( |
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Hi, 1. ;-) after setFields 2. g (0 -9.81 0) Altitude is not taken into account. But, since interFoam solves for p_rgh [p-rho*g*h], the gh term is present in e.g. the calculation of driving flux phi, and also in the buoyantPressure boundary condition. Hence my belief that the equations have some inbalance. |
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I was not able to reproduce this error. I first ran blockMesh, setFields, interFoam, then I cleaned the old timedirs. After that I executed the mentioned transformPoints operation and ran interFoam again, without crash. |
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My error. Does not crash with original settings, but gives different result. I realize that it is a sensitive system, and that 1 km is far away. Numerical errors propagating, but the difference in results I get is not very small. E.g. patchIntegrate alpha1 rightWall: original = 0.001, translated 0.0005. |
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Hold on: the solver tries to solve a physical problem, not a theoretical problem per say. The boundaries and case set-up clearly state that it is running at 1km of altitude (where the gravity acceleration should actually be slightly lower); implicitly the pressures are different (density might be affected, but I think it's set to a fixed value) as you indicated with "p_rgh". Therefore, it's only natural that the results aren't exactly the same! edit: p_ref... some solvers use p_ref for this very same reason. Although can't remember if it'll work with interFoam. Now, if you translate the volume in X or Z axis and the results are truly different, then that is indeed a source of concern ;) |
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Due to the p_rgh formulation h is used directly in the discretisation and hence the location of the domain in the h direction will have a slight effect on the results. If h is so large that the values of p_rgh can no longer be represented accurately by double precision numbers the code will diverge. If this particular behaviour is a problem an alternative would be to use (h - h0) rather than h in the formulation of p_rgh and for h0 to be provided as an input, say the bottom or middle of the domain of interest. I decided against this additional complexity when I implemented the p_rgh formulation as it seemed unlikely that the domain would be sufficiently far from the origin to cause problems. However, if it is considired a real issue I can add the option of specifying h0. |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2011-12-14 11:04 | niklas.wikstrom | New Issue | |
| 2011-12-14 11:08 | niklas.wikstrom | Tag Attached: interFoam | |
| 2011-12-14 11:08 | niklas.wikstrom | Tag Attached: multiphase | |
| 2011-12-14 11:25 | wyldckat | Note Added: 0000837 | |
| 2011-12-14 11:49 | niklas.wikstrom | Note Added: 0000840 | |
| 2011-12-14 11:49 | niklas.wikstrom | Note Edited: 0000840 | |
| 2011-12-14 11:50 | niklas.wikstrom | Note Edited: 0000840 | |
| 2011-12-14 12:20 |
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Note Added: 0000841 | |
| 2011-12-14 12:56 | niklas.wikstrom | Note Added: 0000842 | |
| 2011-12-14 14:09 | wyldckat | Note Added: 0000843 | |
| 2011-12-14 14:11 | wyldckat | Note Edited: 0000843 | |
| 2011-12-29 14:44 | henry | Note Added: 0000878 | |
| 2011-12-29 14:44 | henry | Status | new => closed |
| 2011-12-29 14:44 | henry | Assigned To | => henry |
| 2011-12-29 14:44 | henry | Resolution | open => fixed |
