53 lines
2.6 KiB
Plaintext
53 lines
2.6 KiB
Plaintext
Fields are used by dsmcFoam in several ways, some of which are different to
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their use elsewhere in OpenFOAM. None of these fields are solved by partial
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differential equations, they are used either to record simulation data, or to
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supply boundary data.
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In each case there are 11 fields:
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boundaryT, boundaryU:
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The wall and free stream conditions at the boundary are specified for
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velocity and temperature with these fields - only the data on the
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patches is used, the cell data is not. These are the only two fields
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which supply data to the case.
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dsmcRhoN:
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The population of dsmc particles in cells is recorded to visualise how
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well the cell population conditions required for dsmc are met. The
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boundary conditions are zeroGradient because only cell data is
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meaningful.
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fD, q:
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The wall heat flux (q) and force density (fD, i.e. stress vector) is
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recorded with these fields - only the data on wall patches is relevant,
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the cell data is not.
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iDof, internalE, linearKE, momentum, rhoM, rhoN:
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These fields are the densities of extensive quantities in the
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simulation, i.e. of number, mass, momentum, energy. Cell data is
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recorded in the internal field and the boundaryField is used to record
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the data of particles that strike wall patches. The properties of
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particles striking wall faces are weighted by 1/(Un*fA), where Un is the
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normal component of the particle's velocity and fA is the face area.
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This is done so that when intensive quantities, such as velocity or
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temperature, are evaluated on the wall the values are correct this
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allows velocity slip and temperature jump to be evaluated.
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Therefore, the data in these fields on wall patches is of a different
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type to the volume data. This may cause problems when post-processing,
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as any interpolation of these fields will have a artifacts in the near
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wall cells because the values on the faces are radically different.
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This can be overcome by visualising the data uninterpolated, or by
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copying the fields and setting zeroGradient boundary conditions on
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walls. Calculated intensive fields do not have this issue.
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Further fields are produced by dsmcFoam, i.e. dsmcSigmaTcRMax (used in the
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selection of collision partners) and by the fieldAverage (averaging the
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extensive quantity densities) and dsmcFields (calculating intensive quantities,
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i.e. velocity and temperature, from extensive quantities) function objects in
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each case as it runs.
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