View Issue Details
ID | Project | Category | View Status | Date Submitted | Last Update |
---|---|---|---|---|---|
0002558 | OpenFOAM | Bug | public | 2017-05-19 17:09 | 2017-05-19 18:47 |
Reporter | Sahas | Assigned To | henry | ||
Priority | normal | Severity | tweak | Reproducibility | always |
Status | closed | Resolution | no change required | ||
Summary | 0002558: wallShearStress is calculated using nu instead of mu also for multiphase inciompressible solvers (like interFoam) | ||||
Description | May be it is not a bug but current behavior of wallShearStress utility for multiphase solvers can lead to confusion and further mistakes due to using nu instead of mu in wall shear stress evaluation. | ||||
Steps To Reproduce | Run tutorials/multiphase/interFoam/ras/DTCHull. Evaluate wallShearStress and visualize it on the patch named "hull". One can see that wallShearStress is greatest in region of air. Correct values can be obtained using next formula: wallShearStress_correct = wallShearStress*(rho_water*alpha.water+rho_air*(1-alpha.water)) | ||||
Tags | interFoam, multiphase | ||||
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The wallShearStress calculates \f[ Stress = R \dot n \f] where \vartable R | stress tensor n | patch normal vector (into the domain) \endvartable If you want rho*R rather than R you will need to multiply the result by rho. |
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Yes, and for compressible fluid R is evaluated as model.devRhoReff() whereas for incompressible -- as model.devReff() (function Foam::functionObjects::wallShearStress::execute()). In multiphase solver rho is not constant, so this leads to confusion with values of wallShearStress. I think, it is needed to include some description of such behavior in user manual or fix the issue or may be output warning when using wallShearStress with interFoam. |
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It is clear from the description and dimensions of the wall shear stress that it is kinematic rather than dynamic for incompressible solvers and interFoam is an incompressible solver. If you need the wall shear stress to be multiplied by rho why not do that? |
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Ok, it is not a problem. It is just a matter of habit: usually (and physically) wall shear stress is measured in Pa, in case of constant density we can divide it by rho for consistency with incompressible pressure in OpenFOAM. But in interFoam pressure is measured in Pa (due to non-constant density), so for consistency wall shear stress should be also measured in Pa. And again, this is not a problem but a point to pay attention. |
Date Modified | Username | Field | Change |
---|---|---|---|
2017-05-19 17:09 | Sahas | New Issue | |
2017-05-19 17:09 | Sahas | Tag Attached: interFoam | |
2017-05-19 17:09 | Sahas | Tag Attached: multiphase | |
2017-05-19 17:29 | henry | Note Added: 0008166 | |
2017-05-19 17:29 | henry | Assigned To | => henry |
2017-05-19 17:29 | henry | Status | new => closed |
2017-05-19 17:29 | henry | Resolution | open => no change required |
2017-05-19 17:32 | Sahas | Status | closed => feedback |
2017-05-19 17:32 | Sahas | Resolution | no change required => reopened |
2017-05-19 17:36 | Sahas | Note Added: 0008168 | |
2017-05-19 17:36 | Sahas | Status | feedback => assigned |
2017-05-19 17:58 | henry | Note Added: 0008169 | |
2017-05-19 18:23 | Sahas | Note Added: 0008170 | |
2017-05-19 18:47 | henry | Status | assigned => closed |
2017-05-19 18:47 | henry | Resolution | reopened => no change required |