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Wall shear stress

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Old   February 12, 2008, 18:16
Default Hello, I'm trying to figure ou
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Andrew Burns
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Hello, I'm trying to figure out the dimensions of openFoam's wall shear stress. I'm trying to compare the same mesh run for the same conditions in both fluent and openFoam, however when I use wallShearStress to find the stress on the openFoam case I get numbers that are much different to those from fluent.

I know fluent calculates wall shear stress in pascals, however when I look at the dimensions in the shear stress file generated by openFoam I see this:

[0 2 -2 0 0 0 0]

Wouldn't this mean the units for shear stress in openFoam are m^2/s^2 ? I don't understand how this can be converted to pascals for comparison purposes.

For an idea of the differences I'm talking about, fluent reports the maximum shear stress as 14 pascals, while openFoam reports it as 53.6.
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Old   February 13, 2008, 02:44
Default For an incompressible flow, al
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For an incompressible flow, all the equations are divided with density. If you divide [Pa] with r, it should go like this:
Pa/r = N/m2/kg/m3 = kg*m/s2/m2/kg/m3 = m2/s2

I hope this is helpful!
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Old   February 13, 2008, 17:40
Default Thanks that's perfect. I thoug
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Thanks that's perfect. I thought it would be something like that but I wasn't able to work out if it made sense dimensionally.
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