CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Bugs (http://www.cfd-online.com/Forums/openfoam-bugs/)
-   -   Shear rate error (http://www.cfd-online.com/Forums/openfoam-bugs/62376-shear-rate-error.html)

eugene November 20, 2008 10:31

Line 61 viscosityModel.C shoul
 
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()

henry November 20, 2008 11:13

Not all shear-dependent viscos
 
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.

H


All times are GMT -4. The time now is 17:17.