Hello,
I'm trying to set up a 2D diffusion problem. I noticed that if i
print(shape(CellVariable.value)) after defining a CellVariable I get the
output (2000,) for example.. which isn't a 2D array. I decided to test the
2D diffusion example provided, but I encounter the "RuntimeError: Factor is
exactly singular" and it also will not plot. It is copied straight from the
mesh.20x20 example, so I'm not sure why it will not run.
from fipy import CellVariable, Grid2D, Viewer, TransientTerm, DiffusionTerm
from fipy.tools import numerix
nx = 20
ny = nx
dx = 1
dy = dx
L = dx * nx
mesh = Grid2D(dx=dx, dy=dy, nx=nx, ny=ny)
phi = CellVariable(name="solution variable", mesh=mesh, value=0.)
D = 1
eq = TransientTerm() == DiffusionTerm(coeff=D)
valueTopLeft = 0
valueBottomRight = 1
X, Y = mesh.faceCenters
facesTopLeft = ((mesh.facesLeft & (Y > L / 2)) | (mesh.facesTop & (X < L / 2)))
facesBottomRight = ((mesh.facesRight & (Y < L / 2)) |
(mesh.facesBottom & (X > L / 2)))
phi.constrain(valueTopLeft, facesTopLeft)
phi.constrain(valueBottomRight, facesBottomRight)
if __name__ == '__main__':
viewer = Viewer(vars=phi, datamin=0., datamax=1.)
viewer.plot()
timeStepDuration = 10 * 0.9 * dx**2 / (2 * D)
steps = 10
for step in range(steps):
eq.solve(var=phi, dt=timeStepDuration)
if __name__ == '__main__':
viewer.plot()
Justin Pothoof
The University of Washington - Department of Chemistry
Pre-Candidacy PhD Student
Ginger Group
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