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Shear rate error

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Old   November 20, 2008, 09:31
Default Line 61 viscosityModel.C shoul
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Eugene de Villiers
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Line 61 viscosityModel.C should be

return (sqrt(2)*mag(symm(fvc::grad(U_))));

to comply with the standard definition of shear rate used in the Non-newtonian viscosity formulations:

SR = sqrt(0.5 * D:D)

where D = grad(U) + grad(U).T()
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Old   November 20, 2008, 10:13
Default Not all shear-dependent viscos
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Not all shear-dependent viscosity models use this definition of shear-rate and the one I originally implemented was defined in term of mag(grad(U)) which is what I implemented. Models defined in terms of other shear-rate definitions can be implemented in a way which over-rides the default simple function. Alternatively the form of the shear-rate could be made run-time selectable.

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