Hello, I am running a simulation of a 1D electrochemical system with an applied constant current boundary condition in which the current density (J) is known to be uniform in space (dJ/dx = 0). The expression for J is J = -1/2*(c-\rho/2)*d(\phi)/dx where \phi is the electric potential and \rho is a parameter. In lines 59 and 60 of my code (http://pastebin.com/mksk9NJf), I wrote code to verify if J is uniform in space using 2 different ways (one using phi.faceGrad and the other using phi.grad):
J_face.setValue(-1.0/2.0*(c.harmonicFaceValue-rho/2.0)*phi.faceGrad) J_cell.setValue(-1.0/2.0*(c-rho/2.0)*phi.grad) The figure below is generated for an applied constant current of 2, so we expect J to be constant at 2. In the figure, the green line is J_face while the blue line is J_cell. It seems that J_cell becomes 1 (which is suspiciously half of 2) on the rightmost cell while J_face is still 2. I would like to ask why J_cell doesn't achieve a value of 2 on the rightmost cell. Thanks! Best, Edwin [image: Inline image 2]
<<J_cell vs. J_face.png>>
fipy_pde_v2.py
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