_FixedBCFaceGradVariable mangles FaceGrad, even with no boundary conditions

[guyer]

It seems like all face gradient components are made orthogonal to the faces?

>>> from fipy import *
>>> mesh = Grid2D(nx=3, ny=3)
>>> x, y = mesh.getCellCenters()
>>> var = CellVariable(mesh=mesh, value=sin(x) * cos(y))
>>> print var.getFaceGrad()
--> print(var.getFaceGrad())
--> print(var.getFaceGrad())
[[ 0.22732436  0.05223661 -0.17508774  0.12282387  0.02822356 -0.09460031
  -0.09460031 -0.0217381   0.07286221 -0.20752402 -0.04768671  0.1598373
   0.          0.45464871 -0.35017549  0.          0.          0.03664678
  -0.02822576  0.          0.         -0.41504803  0.3196746   0.        ]
 [ 0.          0.         -0.         -0.38682227 -0.8048242  -0.48287447
  -0.41800193 -0.86969674 -0.52179638  0.          0.          0.
  -0.19341114 -0.29791162 -0.32192467 -0.24143724 -0.4024121  -0.61983629
  -0.66979795 -0.50233543 -0.20900097 -0.32192467 -0.34787328 -0.26089819]]

but

>>> var2 = CellVariable(mesh=mesh, value=sin(x) * cos(y))
>>> from fipy.variables.fixedBCFaceGradVariable import _FixedBCFaceGradVariable
>>> var2.faceGrad = _FixedBCFaceGradVariable(var2, boundaryConditions=())
>>> print var2.getFaceGrad()
--> print(var2.getFaceGrad())
[[ 0.22732436  0.05223661 -0.17508774  0.          0.          0.          0.
   0.          0.         -0.20752402 -0.04768671  0.1598373   0.
   0.45464871 -0.35017549  0.          0.          0.03664678 -0.02822576
   0.          0.         -0.41504803  0.3196746   0.        ]
 [ 0.          0.          0.         -0.38682227 -0.8048242  -0.48287447
  -0.41800193 -0.86969674 -0.52179638  0.          0.          0.
  -0.19341114  0.          0.         -0.24143724 -0.4024121   0.          0.
  -0.50233543 -0.20900097  0.          0.         -0.26089819]]

Perhaps more readily seen as

>>> from fipy import *
>>> mesh = Grid2D(nx=10, ny=10)
>>> x, y = mesh.getCellCenters()
>>> var = CellVariable(mesh=mesh, value=sin(x) * cos(y))
>>> Viewer(vars=var.getFaceGrad()).plot(filename="normal.png")

vs.

>>> var2 = CellVariable(mesh=mesh, value=sin(x) * cos(y))
>>> from fipy.variables.fixedBCFaceGradVariable import _FixedBCFaceGradVariable
>>> var2.faceGrad = _FixedBCFaceGradVariable(var2, boundaryConditions=())
>>> Viewer(vars=var2.getFaceGrad()).plot(filename="FixedBC.png")

Imported from trac ticket #316, created by guyer on 11-30-2010 at 14:05, last modified: 12-08-2011 at 10:15

[guyer]

guyer attached FixedBC.png on 11-30-2010 at 14:20

[guyer]

guyer attached normal.png on 11-30-2010 at 14:20

[guyer]

_FixedBCFaceGradVariable is obsolete (and was removed in r4526). Use .constrain().

Trac comment by guyer on 12-08-2011 at 10:15