Hi Dr. Guyer,
First I tried getting rid of the square brackets in ConvectionTestProblem2D_01.py (commit ‘changed square brackets to parenthesis in convection BC, but get same…’), but results are the same (still wrong). Next: As you directed, I took a look at: https://github.com/usnistgov/fipy/blob/develop/documentation/USAGE.rst#applying-robin-boundary-conditions Firefox was showing me raw latex rather than human-readable equations at that web address, so I made a version I could read using the kile editor: https://github.com/cashTangoTangoCash/Convection2DFiPyExample01/blob/master/RobinBoundaryConditionsFiPyUsage.pdf That material is rather challenging for me. I took a stab at it, resulting in: commit: ‘made a first attempt at a formulation in view of suggestions by fipy …’ ConvectionTestProblem2D_01_2ndTry.py https://github.com/cashTangoTangoCash/Convection2DFiPyExample01/blob/fb47960548650c994eb0c6f990e0db297566e174/ConvectionTestProblem2D_01_2ndTry.py a few handwritten notes indicating what I was thinking: https://github.com/cashTangoTangoCash/Convection2DFiPyExample01/blob/master/RobinBoundaryConditionsFiPyUsageConvectionBC.pdf Here is a bit of the code: #ref: https://github.com/usnistgov/fipy/blob/develop/documentation/USAGE.rst#applying-robin-boundary-conditions #warning: avoid confusion between convectionCoeff in that fipy documentation, which refers to terms involving "a", and convectionCoeff here, which refers to a heat transfer convection coefficient at a boundary Gamma0=D_thermal Gamma = FaceVariable(mesh=mesh, value=Gamma0) mask=surfaceFaces Gamma.setValue(0., where=mask) dPf = FaceVariable(mesh=mesh, value=mesh._faceToCellDistanceRatio * mesh.cellDistanceVectors) Af = FaceVariable(mesh=mesh, value=mesh._faceAreas) #RobinCoeff = (mask * Gamma0 * Af / (dPf.dot(a) + b)).divergence #a is zero in our case b=1. RobinCoeff = (mask * Gamma0 * Af / b).divergence #a is zero in our case #eq = (TransientTerm() == DiffusionTerm(coeff=Gamma) + RobinCoeff * g - ImplicitSourceTerm(coeff=RobinCoeff * mesh.faceNormals.dot(a))) #a is zero in our case # g in this formulation is -convectionCoeff/k*var, where var=T-T_infinity eq = (TransientTerm() == DiffusionTerm(coeff=Gamma) + ImplicitSourceTerm(RobinCoeff * -convectionCoeff/k)) Now the solution variable remains stuck at the initial condition, as if the boundary condition is not being applied. I am sort of out of my depth at this point. I was guessing that an ImplicitSourceTerm was the right thing to do, since 'g' in the Robin condition depends on the solution variable. I did mess around a little in IPython seeing if any terms are coming out all zeros. Again, I put everything at https://github.com/cashTangoTangoCash/Convection2DFiPyExample01. Thanks On Mon, Dec 3, 2018 at 4:21 PM Guyer, Jonathan E. Dr. (Fed) via fipy < fipy@nist.gov> wrote: > Drew - > > Apologies for the delayed reply. > > There are a couple of issues here: > > `-convectionCoeff/k*(var.faceValue-T_infinity)` describes a FiPy > FaceVariable. > > `[-convectionCoeff/k*(var.faceValue-T_infinity)]` is a single element > Python list that contains a FiPy FaceVariable. > > Multiplying that list by other elements has rather unpredictable results. > > In short, get rid of the square brackets. We do our best to treat Python > lists like FiPy vector fields, but there's only so much we can do. A list > that holds a numpy array is not a vector field. > > > Beyond that, what you've described looks like a Robin boundary condition > to me. Our best recommendation for Robin conditions is covered at: > > > https://github.com/usnistgov/fipy/blob/develop/documentation/USAGE.rst#applying-robin-boundary-conditions > > Please don't hesitate to ask for more clarification if this doesn't get > you where you need. > > - Jon > > > > > On Nov 16, 2018, at 11:55 PM, Drew Davidson <davidson...@gmail.com> > wrote: > > > > Hello, > > > > I am stuck in how to correctly apply a simple convection boundary > condition in FiPy, in the context of simple transient heat conduction in 2D. > > > > Is this correct: > > > var.faceGrad.constrain([-convectionCoeff/k*(var.faceValue-T_infinity)]*mesh.faceNormals,where=surfaceFaces) > > > > I have a 2D mesh generated in gmsh. The convection boundary condition is > applied to a curved boundary. > > > > The code and results are found at: > > > https://github.com/cashTangoTangoCash/Convection2DFiPyExample01/tree/master > > > > The project appears to have a heap of files, but It’s a really just a > simple 2D problem with a comparison to an analytical solution. The basic > script is ConvectionTestProblem2D_01.py. Report20181116.pdf shows current > results, which are clearly wrong. > > > > Am I correctly applying the convection boundary condition in terms of > the FiPy syntax/language for this 2D problem with a gmsh mesh and a curved > boundary? > > > > Thanks > > _______________________________________________ > > fipy mailing list > > fipy@nist.gov > > http://www.ctcms.nist.gov/fipy > > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] > > > _______________________________________________ > fipy mailing list > fipy@nist.gov > http://www.ctcms.nist.gov/fipy > [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ] >
_______________________________________________ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
