View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0001769 | OpenFOAM | Bug | public | 2015-06-30 08:26 | 2015-06-30 20:06 |
| Reporter | ALU | Assigned To | henry | ||
| Priority | normal | Severity | minor | Reproducibility | always |
| Status | resolved | Resolution | fixed | ||
| Platform | GNU/Linux | OS | Ubuntu | OS Version | 14.04 |
| Summary | 0001769: wrong calcutation using field function object cellSource weightedAverage | ||||
| Description | The field function object cellSource calculates wrong values using weightedAverage. result = sum(values)/sum(weightField) This only gives right values if every cell in the mesh has the same volume. The modification result = sum(values*V)/sum(V*weightField) gives the right results for some reason. (I would expect result = sum(values*V*weightField)/sum(V*weightField).) The same problem may occur with faceSorce (not tested). | ||||
| Steps To Reproduce | Calculate the mass weighted average of a T field using rho as weightField. Compare the results using different meshes (homogeneous and not homogeneous). | ||||
| Tags | No tags attached. | ||||
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> gives the right results for some reason. > (I would expect result = sum(values*V*weightField)/sum(V*weightField).) This is a consequence of the // apply weight field values *= weightField; in writeValues. This separation of operations is VERY confusing, I will look into changing it. At the moment the volume average and volume integrate multiply by the cell-volumes but weighted average does not; it assumes that if you wanted to weight by rho*V the weighting field would be rho*V. This may be a bit inconvenient but if we include the volumes in the expression it would not be possible to calculate a weighted average without the volumes should it be required. Probably the best solution would be to add a new processing function which calculates the weighted volume average. |
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Resolved in OpenFOAM-dev by commit 2127051ad542c47ae0652b5783ab1f9a667959f4 cellSource: Added weightedVolAverage option faceSource: Added weightedAreaAverage option |
