Re: [fipy] Problem using mix of periodic and non-periodic BCs
Awesome. Thanks a lot!
Daniel Wheeler schrieb am Freitag, 19. April 2024 um 16:41:35 UTC+2:
> Here's an example. It's trivial, but it just demonstrates solving a
> variable on one grid and then using that variable to set the value of
> the diffusion coefficient for an equation on a different grid.
> Obviously, if the domains don't overlap then you need to take care of
> the mapping and interpolation between the grids.
>
> ~~~
> from fipy import CellVariable, Grid1D, DiffusionTerm, Viewer, TransientTerm
>
> nx = 100
> dt = 1e-3
> Lx = 1.0
> steps = 1000
>
> mesh0 = Grid1D(nx=nx, Lx=Lx)
> mesh1 = Grid1D(nx=nx, Lx=Lx)
>
> v0 = CellVariable(mesh=mesh0, value=0., hasOld=True)
> v0.constrain(1e-1, where=mesh0.facesLeft)
> v0.constrain(10., where=mesh0.facesRight)
>
> v1 = CellVariable(mesh=mesh1, value=0., hasOld=True)
> v1.constrain(0., where=mesh1.facesLeft)
> diff_coeff = CellVariable(mesh=mesh1, value=0.)
>
> eqn0 = TransientTerm() == DiffusionTerm()
> eqn1 = TransientTerm() == DiffusionTerm(diff_coeff) + 1.
>
> viewer = Viewer(v1)
>
> for i in range(steps):
> v0.updateOld()
> v1.updateOld()
> eqn0.solve(v0, dt=dt)
> diff_coeff[:] = v0
> eqn1.solve(v1, dt=dt)
> viewer.plot()
>
> input("stopped")
>
>
> On Thu, Apr 18, 2024 at 3:31 AM Nils Winkler wrote:
> >
> > Oh great. Do you happen to have example code? I am not sure how to
> properly do that.
> >
> > Daniel Wheeler schrieb am Mittwoch, 17. April 2024 um 16:19:16 UTC+2:
> >>
> >> On Wed, Apr 17, 2024 at 9:33 AM Nils Winkler
> wrote:
> >> >
> >> > Hi,
> >> >
> >> > I am using fipy to deal with a system of three coupled nonlinear
> partial differential equations. Two dependent parameters have Naumann BCs
> and one periodic BCs. Is it possible to implement these at the same time?
> >> >
> >> > Using only a periodic mesh with internal BCs for the Naumann BC does
> not work because the respective two dependent parameters are not continuous
> at the boundary.
> >> > Can one somehow combine a periodic with a normal mesh? Or is it
> possible to use a normal mesh and impose periodic boundary conditions
> internally?
> >>
> >> Yes, you can do that. You'll have to define the dependent variables
> >> across both the domains and map the variable values over at each sweep
> >> / timestep so there will be some overhead.
> >>
> >> --
> >> Daniel Wheeler
>
>
>
> --
> Daniel Wheeler
>
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Re: [fipy] Problem using mix of periodic and non-periodic BCs
Here's an example. It's trivial, but it just demonstrates solving a
variable on one grid and then using that variable to set the value of
the diffusion coefficient for an equation on a different grid.
Obviously, if the domains don't overlap then you need to take care of
the mapping and interpolation between the grids.
~~~
from fipy import CellVariable, Grid1D, DiffusionTerm, Viewer, TransientTerm
nx = 100
dt = 1e-3
Lx = 1.0
steps = 1000
mesh0 = Grid1D(nx=nx, Lx=Lx)
mesh1 = Grid1D(nx=nx, Lx=Lx)
v0 = CellVariable(mesh=mesh0, value=0., hasOld=True)
v0.constrain(1e-1, where=mesh0.facesLeft)
v0.constrain(10., where=mesh0.facesRight)
v1 = CellVariable(mesh=mesh1, value=0., hasOld=True)
v1.constrain(0., where=mesh1.facesLeft)
diff_coeff = CellVariable(mesh=mesh1, value=0.)
eqn0 = TransientTerm() == DiffusionTerm()
eqn1 = TransientTerm() == DiffusionTerm(diff_coeff) + 1.
viewer = Viewer(v1)
for i in range(steps):
v0.updateOld()
v1.updateOld()
eqn0.solve(v0, dt=dt)
diff_coeff[:] = v0
eqn1.solve(v1, dt=dt)
viewer.plot()
input("stopped")
On Thu, Apr 18, 2024 at 3:31 AM Nils Winkler wrote:
>
> Oh great. Do you happen to have example code? I am not sure how to properly
> do that.
>
> Daniel Wheeler schrieb am Mittwoch, 17. April 2024 um 16:19:16 UTC+2:
>>
>> On Wed, Apr 17, 2024 at 9:33 AM Nils Winkler wrote:
>> >
>> > Hi,
>> >
>> > I am using fipy to deal with a system of three coupled nonlinear partial
>> > differential equations. Two dependent parameters have Naumann BCs and one
>> > periodic BCs. Is it possible to implement these at the same time?
>> >
>> > Using only a periodic mesh with internal BCs for the Naumann BC does not
>> > work because the respective two dependent parameters are not continuous at
>> > the boundary.
>> > Can one somehow combine a periodic with a normal mesh? Or is it possible
>> > to use a normal mesh and impose periodic boundary conditions internally?
>>
>> Yes, you can do that. You'll have to define the dependent variables
>> across both the domains and map the variable values over at each sweep
>> / timestep so there will be some overhead.
>>
>> --
>> Daniel Wheeler
--
Daniel Wheeler
--
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View this message at https://list.nist.gov/fipy
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Re: [fipy] Problem using mix of periodic and non-periodic BCs
Oh great. Do you happen to have example code? I am not sure how to properly do that. Daniel Wheeler schrieb am Mittwoch, 17. April 2024 um 16:19:16 UTC+2: > On Wed, Apr 17, 2024 at 9:33 AM Nils Winkler wrote: > > > > Hi, > > > > I am using fipy to deal with a system of three coupled nonlinear partial > differential equations. Two dependent parameters have Naumann BCs and one > periodic BCs. Is it possible to implement these at the same time? > > > > Using only a periodic mesh with internal BCs for the Naumann BC does not > work because the respective two dependent parameters are not continuous at > the boundary. > > Can one somehow combine a periodic with a normal mesh? Or is it possible > to use a normal mesh and impose periodic boundary conditions internally? > > Yes, you can do that. You'll have to define the dependent variables > across both the domains and map the variable values over at each sweep > / timestep so there will be some overhead. > > -- > Daniel Wheeler > -- To unsubscribe from this group, send email to [email protected] View this message at https://list.nist.gov/fipy To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
Re: [fipy] Problem using mix of periodic and non-periodic BCs
On Wed, Apr 17, 2024 at 9:33 AM Nils Winkler wrote: > > Hi, > > I am using fipy to deal with a system of three coupled nonlinear partial > differential equations. Two dependent parameters have Naumann BCs and one > periodic BCs. Is it possible to implement these at the same time? > > Using only a periodic mesh with internal BCs for the Naumann BC does not work > because the respective two dependent parameters are not continuous at the > boundary. > Can one somehow combine a periodic with a normal mesh? Or is it possible to > use a normal mesh and impose periodic boundary conditions internally? Yes, you can do that. You'll have to define the dependent variables across both the domains and map the variable values over at each sweep / timestep so there will be some overhead. -- Daniel Wheeler -- To unsubscribe from this group, send email to [email protected] View this message at https://list.nist.gov/fipy To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
