Try this:
#!/usr/bin/env python
from fipy import *
## my mesh and subdivisions and time variable
Lx = 10.0
Ly = 10.0
Nx = 20.0
Ny = 20.0
Dx = Lx/Nx
Dy = Ly/Ny
t = Variable(value=0.0)
## create mesh
m2D = Grid2D(nx=Nx, ny=Ny, dx=Dx, dy=Dy)
x, y = m2D.getFaceCenters()
## define diffusion coefficients and different material along top edge of box
nominalDiffusionCoef = 0.1
D = FaceVariable(mesh=m2D, value=nominalDiffusionCoef)
D.setValue(3 * nominalDiffusionCoef, where = (y > 9))
## define sources - not using at present
## boundarySource = FaceVariable(mesh=m2D, value = 0.0, rank=1)
## boundarySource.setValue(-1, where = m2D.getExteriorFaces() )
## other things I tried
## eq = TransientTerm() == ImplicitDiffusionTerm(coeff=D) + cv * t
## eq = TransientTerm() == ImplicitDiffusionTerm(coeff=D) +
boundarySource.getDivergence()
# Use the simple one
eq = TransientTerm() == ImplicitDiffusionTerm(coeff=D)
## set up boundary conditions
facesHeaters = (m2D.getFacesRight())
# want flux to go to zero after a set time
BCs = ( FixedFlux(faces=facesHeaters, value = -0.5 * (t < 3) ))
phi = CellVariable(name = "solution variable",
mesh = m2D,
value = 1.0)
dt = 0.9 * Dx*Dy / (2 * 1.0)
## setup viewer and end-time
totalTime=10
viewer=Viewer(vars=phi)
viewer.plot()
while t < totalTime:
eq.solve(var=phi, boundaryConditions=BCs, dt=dt)
viewer.plot()
t.setValue(t.getValue()+dt)
print t < 3, t ## check
raw_input("Press <return> to proceed...")
On Wed, May 20, 2009 at 12:11 AM, david wende <[email protected]> wrote:
> Hi Gurus,
>
> This is a continuation of my attempts to model a bit of silicon being
> heated by a pulse of laser.
> I am also including the top metal layer as a change in diffusion coef.
>
> Modelling the heating by a FixedFlux along the right hand side, and would
> like it to be non-zero before time T, and zero after time T.
>
> Eventually I would include some convection/radiation terms along
> the other 3 sides, but that is not included yet (doing this bit by bit).
>
> I am having trouble making the flux go to zero. The signum function is
> working and printing out OK, but it seems that when a BC has a time
> dependent term, something goes wrong.
>
> Here is the code:
>
> #!/usr/bin/env python
> from fipy import *
> def signum ():
> """ This returns 1 or 0 depending on time """
>
> if 3.0 > t:
> return 1.0
> else:
> return 0.0
>
> ## my mesh and subdivisions and time variable
> Lx = 10.0
> Ly = 10.0
> Nx = 20.0
> Ny = 20.0
> Dx = Lx/Nx
> Dy = Ly/Ny
> t = Variable(value=0.0)
>
> ## create mesh
> m2D = Grid2D(nx=Nx, ny=Ny, dx=Dx, dy=Dy)
> x, y = m2D.getFaceCenters()
>
> ## define diffusion coefficients and different material along top edge of
> box
> nominalDiffusionCoef = 0.1
> D = FaceVariable(mesh=m2D, value=nominalDiffusionCoef)
> D.setValue(3 * nominalDiffusionCoef, where = (y > 9))
>
> ## define sources - not using at present
> ## boundarySource = FaceVariable(mesh=m2D, value = 0.0, rank=1)
> ## boundarySource.setValue(-1, where = m2D.getExteriorFaces() )
> ## other things I tried
> ## eq = TransientTerm() == ImplicitDiffusionTerm(coeff=D) + cv * t
> ## eq = TransientTerm() == ImplicitDiffusionTerm(coeff=D) +
> boundarySource.getDivergence()
>
> # Use the simple one
> eq = TransientTerm() == ImplicitDiffusionTerm(coeff=D)
>
> ## set up boundary conditions
> facesHeaters = (m2D.getFacesRight())
> # want flux to go to zero after a set time
> BCs = ( FixedFlux(faces=facesHeaters, value = -0.5 * signum() ))
>
> phi = CellVariable(name = "solution variable",
> mesh = m2D,
> value = 1.0)
>
> dt = 0.9 * Dx*Dy / (2 * 1.0)
>
> ## setup viewer and end-time
> totalTime=10
> viewer=Viewer(vars=phi)
> viewer.plot()
>
> while t() < totalTime:
> eq.solve(var=phi, boundaryConditions=BCs, dt=dt)
> viewer.plot()
> t.setValue(t()+dt)
> print signum(), t ## check
>
> raw_input("Press <return> to proceed...")
>
> Could you help?
>
> Thanks a lot
>
> --
> David Wende
> home +972-8-9353488
> work +972-2-5886116
> mobile +972-54-234-6479
>
--
Daniel Wheeler
