I’ve had some trouble using fipy for the 1D, steady-state ternary electrolyte problem, which involves coupled, nonlinear migration and diffusion.
A text version of the model is listed below. A more complete development is at http://bit.ly/2wJDXob from fipy import * # Parameters nx=50 C20=4.0/3.0 z1, z2, z3= 2.0, -2.0, 1.0 # Mesh mesh = Grid1D(nx=nx, dx=1.0/nx) # Variables C1= CellVariable(mesh = mesh, value = 1.0) C2= CellVariable(mesh = mesh, value = 4.0/3.0) Phi = CellVariable(mesh = mesh, value = -0.5) # Electroneutrality C3 = -1/z3 * (z1*C1 + z2*C2) # Boundary Conditions C1.constrain(1.0, mesh.facesRight) C1.constrain(0.0, mesh.facesLeft) C2.constrain(C20, mesh.facesRight) Phi.constrain(0, mesh.facesRight) # Governing Equations Eq1 = DiffusionTerm(coeff=z1*C1, var=Phi) + DiffusionTerm(coeff=1.0, var=C1) Eq2 = DiffusionTerm(coeff=z2*C1, var=Phi) + DiffusionTerm(coeff=1.0, var=C2) Eq3 = DiffusionTerm(coeff=z3*C3, var=Phi) + (C3.faceGrad).divergence Eqns = Eq1 & Eq2 & Eq3 # Solution res = 1e+10 restol= 1e-3 while res > restol: res = Eqns.sweep() print(res) However, this system does not converge. I suspect the issue is with boundary conditions. I’ve tried zeroing out the diffusion coefficients at the boundary, but that does not seem to make a difference here. I am able to use this approach for the analogous binary problem: http://bit.ly/2wOzxfK Any insights or suggestions would be welcome. Cheers, Scott☘ _______________________________________________ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
