Thanks for your quick reply
The system I want to describe is a tube, which has a defined temperature at the
outside. Inside the tube is the fluid with the velocity of v_f. The Fluid is
cold and shall get a heat flux about the wall of the tube. My domain feature is
the fluid surrounded by a tube. The inside of the tube is touching the boundary
of the Fluid.
I am working in 2D and both, the tube and the fluid, are included in my file.
The file is a little bit larger, but I try to post the most important things.
I define for both, the tube and the fluid, separated meshs, so that the systems
will solve one after another. The both systems are linked about their boundary
conditions. And I want to solve the steady state solution, thus I iterate the
both systems in a “while loop” till the temperature profiles are constant.
tube = CellVariable(name="temperature [C]", mesh=mesh,value = 0.)
nx = 100
ny = nx
dx = D_r/100 #D_r is the size of the tube
dy = L/100
mesh = Grid2D(dx=dx, dy=dy, nx=nx, ny=ny)
boundaryConditionsWand = (
FixedValue(faces=mesh.getFacesRight(), value=Fluid(1,0,6000)),
FixedFlux(faces=mesh.getFacesLeft(),
value=-h_rs*a_rs*(tube(1,0,6000)-Fluid(1,0,6000)))
tube.equation = (ImplicitDiffusionTerm(coeff=k_r))
tube.equation.solve(var=tube, boundaryConditions=boundaryConditionsWand,
solver=DefaultAsymmetricSolver(tolerance=1.e-100, iterations=10000))
T_w=tube
this give me the temperature of the tube. and now I solve the fluid:
Fluid = CellVariable(name="temperature [C]", mesh=mesh,value = 0.)
nz = 100
nr = nz
dz = L/100
dr = D/200
mesh = CylindricalGrid2D(dr=dr, dz=dz, nr=nr, nz=nz)
boundaryConditionsFluid = (
FixedFlux(faces=mesh.getFacesTop(), value=0),
FixedValue(faces=mesh.getFacesBottom(), value=T_ef),
FixedFlux(faces=mesh.getFacesLeft(),
value=h_rf*a_rf*(tube(1,0,6000)-Fluid(1,0,6000))),
FixedFlux(faces=mesh.getFacesRight(),
value=h_rf*a_rf*(tube(1,0,6000)-Fluid(1,0,6000))))
Fluid.equation = ImplicitDiffusionTerm(coeff=k_fg)==
rho*cp*ExplicitUpwindConvectionTerm(coeff=((v_f,)))
Fluid.equation.solve(var=Fluid,
boundaryConditions=boundaryConditionsFluid,
solver=DefaultAsymmetricSolver(tolerance=1.e-100, iterations=10000))
T_f=Fluid
The solution gives me the temperature profiles, but I use a FixedFlux and I
want that the Flux will be calculate in each cell of the system.
How can I write it?
-------- Original-Nachricht --------
> Datum: Wed, 5 May 2010 11:44:53 -0400
> Von: William Gathright <[email protected]>
> An: Multiple recipients of list <[email protected]>
> Betreff: Re: flux boundary
>
> Hi Alexander,
> I would suggest that we need a little more information about your
> problem to be as helpful as possible. Are you working in 1D or 2D?
> Are both the tube and the fluid included in your simulation domain, or
> just the tube?
>
> The reason I ask is that the boundary conditions are designed to be
> applied at the external faces of your domain. For example, if your
> domain features a tube surrounded by a fluid, the boundary conditions
> should only pertain to the fluid (since the fluid is the only thing
> touching the boundary of your domain).
>
> If you want a flux that is calculated in every cell of your system,
> you'll get that by solving your heat equations. For that, you may
> want to try declaring "Heat" or "Temperature" to be your CellVariable
> instead of "Fluid" or "Tube". Again, with a little more information
> about your problem and your code we may be able to provide more
> detailed help.
>
> - Will Gathright
> Rensselaer Polytechnic Institute
> Department of Materials Science and Engineering
>
> On Wed, May 5, 2010 at 11:14 AM, Alexander Holbach <[email protected]>
> wrote:
> >
> > Hi,
> > I am using the PDE solver in a system.
> > But I have problems with my boundarys. The system shall simulate a heat
> transfer from tube to Fluid. So I wrote two systems with two seperated PDE
> solvers.
> >
> > I'd like to know how I may implement the following boundary condition
> over the right and left faces:
> > the equations are:
> >
> > …
> > tube = CellVariable(name="temperature [C]", mesh=mesh,value = 0.)
> > tube.equation = (ImplicitDiffusionTerm(coeff=k_r))
> > tube.equation.solve(var=tube,
> > boundaryConditions=boundaryConditionsWand,
> > solver=DefaultAsymmetricSolver(tolerance=1.e-100,
> iterations=10000))
> >
> > …
> > and
> > …
> >
> > Fluid = CellVariable(name="temperature [C]", mesh=mesh,value = 0.)
> > Fluid.equation = ImplicitDiffusionTerm(coeff=k_fg)==
> rho*cp*ExplicitUpwindConvectionTerm(coeff=((v_f,)))
> > Fluid.equation.solve(var=Fluid,
> > boundaryConditions=boundaryConditionsFluid,
> > solver=DefaultAsymmetricSolver(tolerance=1.e-100,
> iterations=10000))
> >
> > and now I want to implement the boundary condition, that there is a Flux
> in each mesh cell from the tube to the Fluid.
> > What I can write is:
> > …
> >
> > FixedFlux(faces=mesh.getFacesLeft(),
> value=h_rf*a_rf*(tube(1,0,6000)-Fluid(1,0,6000))),
> > FixedFlux(faces=mesh.getFacesRight(),
> value=h_rf*a_rf*(tube(1,0,6000)-Fluid(1,0,6000))))
> > …
> >
> > but this is a fix Flux and I want that the Flux will be calculate in
> each cell of the system.
> >
> > Is this possible?
> >
> > Thank for your help
> > Alexander
> > --
> > GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
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> >
> >
>
--
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