Hi Adrian,
It's a little bit of a hack, but I got something to work, see below.
Unfortunately, I think you need to explicitly delete the fixed value
constraint from the CellVariable's faceConstraints list, which
requires some knowledge of FiPy's internals and remember the order in
which the constraints were added. I would be nice if "var.constrain"
returned some sort of constraint object which could be deleted.
Cheers,
Daniel
~~~~
import fipy as fp
mesh = fp.Grid1D(nx=10)
var = fp.CellVariable(mesh=mesh, value=0.)
var.constrain(1., mesh.facesLeft)
var.constrain(0., mesh.facesRight)
eqn = fp.TransientTerm() == fp.DiffusionTerm()
viewer = fp.Viewer(var)
dt = 0.1
for _ in range(100):
eqn.solve(var, dt=dt)
viewer.plot()
del var.faceConstraints[0]
var.faceGrad.constrain(1., mesh.facesLeft)
for _ in range(1000):
eqn.solve(var, dt=dt)
viewer.plot()
~~~~
On Wed, Jun 21, 2017 at 2:56 PM, Adrian Jacobo
<ajac...@mail.rockefeller.edu> wrote:
> Hi All,
>
> I have a problem where I would want to specify fixed value boundary
> conditions for times t<t0 and then switch to fixed gradient boundary
> conditions for t>=t0. The way I've implemented this is:
>
>
> a.constrain(a_0,(mesh.exteriorFaces))
>
> while t<tottime:
> if t > = t0:
> a.faceGrad.constrain(0.,mesh.exteriorFaces)
> eq.solve(dt=timeStepDuration)
> t+=dt
>
> But what it seems to be happening is that the fixed value bc is not
> being overwritten by the fixed gradient one. How can I do to remove the
> fixed value bc? Is there a way to check the boundary conditions on a
> variable?
>
> Thanks,
> Adrian.
>
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--
Daniel Wheeler
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