dolfin team mailing list archive

[Alexander Jarosch <alexanj@xxxxx>]

Hi,

I have a rather simple question I guess. I tried to figure out how to 
give the stokes solver a viscosity for each vertex and started of with 
the stokes solver with a constant viscosity nu:

modified from Anders file:
---------------
P1 = FiniteElement("Lagrange", "triangle", 1)
P2 = FiniteElement("Vector Lagrange", "triangle", 2)
TH = P2 + P1

(v, q) = BasisFunctions(TH)
(u, p) = BasisFunctions(TH)
nu     = Constant()    #viscosity


f = Function(P2)

a = (dot(nu*grad(u), grad(v)) - p*div(v) + div(u)*q)*dx
L = dot(f, v)*dx
---------------

now that works fine and now i have the viscosity values for each vertex 
in a vector as values and in a function like:

Function viscfunc(viscosity, mesh, element);

Now i tried to get a form file which takes these values like:
---------------
P1 = FiniteElement("Lagrange", "triangle", 1)
P2 = FiniteElement("Vector Lagrange", "triangle", 2)
element1 = FiniteElement("Discontinuous vector Lagrange", "triangle", 0, 1)


TH = P2 + P1

(v, q) = BasisFunctions(TH)
(u, p) = BasisFunctions(TH)
nu     = Function(element1)    #viscosity

f = Function(P2)

a = (dot(dot(nu, grad(u)), grad(v)) - p*div(v) + div(u)*q)*dx
L = dot(f, v)*dx
---------------

well and it does not work, as well as the approach like:

---------------
P1 = FiniteElement("Lagrange", "triangle", 1)
P2 = FiniteElement("Vector Lagrange", "triangle", 2)
constant_scalar = FiniteElement("Discontinuous Lagrange", "triangle", 1)


TH = P2 + P1

(v, q) = BasisFunctions(TH)
(u, p) = BasisFunctions(TH)
nu     = Function(constant_scalar)    #viscosity
#nu     = Constant()

f = Function(P2)

a = (dot(nu*grad(u), grad(v)) - p*div(v) + div(u)*q)*dx
L = dot(f, v)*dx
---------------

which actually takes my viscosity vector and starts to solve but does 
not converge.

might be a simple mistake in there, I appreciate any help or hints.

Alex