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question on "specified flux" BC for UDS

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Old   June 18, 2010, 16:11
Default question on "specified flux" BC for UDS
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I have a question about setting the “specified flux” boundary condition for UDS equations. I defined a UDS to solve the electrical potential, and tried to set a fixed current density at the cathode. From the User’s guide, it seems that the “specified flux” is the dot product of the gradient of the UDS and the unit normal of the surface, multiplied by the diffusion coefficient. According to this definition, the “specified flux” for this electrical potential equation should be the magnitude of the current density at the surface. Do I understand right?
Then I calculated the current density using a UDF, so that I can display it on surfaces. Then I found that the current density displayed on the cathode surface is not what I specified as BC!! And their direction is not normal to the surface either!
I’m really confused. Can anyone please help me? Many thanks!
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