sign issues for equation with transient, convection and implicit terms

[wd15]

The following breaks when the sign is changed on the equation

from fipy import Grid1D, CellVariable
from scipy import exp
from fipy import TransientTerm, ConvectionTerm, ImplicitSourceTerm, Viewer

xmax = 5.
dx = 0.05
nx = xmax/dx
mesh = Grid1D(dx=dx, Lx=xmax)

x = mesh.getCellCenters()[0]
X = mesh.getFaceCenters()[0]

numerical = CellVariable(name="numerical", mesh=mesh)

numerical.constrain(1, mesh.facesLeft)
numerical.constrain(0, mesh.facesRight)
numerical.faceGrad.constrain([0], mesh.facesLeft)

analytical = CellVariable(name="analytical value", mesh=mesh)
analytical.setValue(exp(-x**2/2.))

eqn = TransientTerm(coeff=1 / x) == \
  - ConvectionTerm(coeff=[[1]]) \
  - ImplicitSourceTerm(coeff=x)

numerical.setValue(exp(-x**2/2.))

vi = Viewer(vars=(numerical,analytical),datamin=0,datamax=2)

for i in range(10000):
eqn.solve(var=numerical,dt=1.)
vi.plot()
raw_input('stopped')

Imported from trac ticket #465, created by wd15 on 09-20-2012 at 12:23, last modified: 09-27-2012 at 10:07

[wd15]

Pull request

The following changes since commit 084d3649a015f07b0cb3856038de5c53d03a391a:

  Merge branch 'loki-test-failures-rebase' into develop (2012-09-05 16:21:50 -0400)

are available in the git repository at:

  ssh://genie.nist.gov//users/wd15/git/fipy ticket465-sign-issues-rebase

Daniel Wheeler (1):
Fix for issue #342, using diagonalSign with convection terms.

 fipy/terms/abstractConvectionTerm.py |   53 +++++++++++++++++++++++++--------
 fipy/terms/cellTerm.py               |    1 -
 fipy/terms/implicitSourceTerm.py     |   16 ++--------
 fipy/terms/nonDiffusionTerm.py       |   14 +++++++++
 fipy/terms/term.py                   |    9 ++++-
 fipy/terms/upwindConvectionTerm.py   |    3 +-
 6 files changed, 65 insertions(+), 31 deletions(-)

Trac comment by wd15 on 09-21-2012 at 16:33

[guyer]

Replying to wd15:

Pull request

These changes (again) look reasonable.

Trac comment by guyer on 09-25-2012 at 12:04

[wd15]

Changes merged with 2a422a6 and 23c8412

Trac comment by wd15 on 09-27-2012 at 10:07