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[Johan Hake <question152076@xxxxxxxxxxxxxxxxxxxxx>]

Question #152076 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/152076

Johan Hake posted a new comment:
The below code works for me. You are initialzing a Function from a 
FunctionSpace with value size 2, which is done as you present.

If you want to set the initial conditions for the whole solution vector you 
need an Expression with value_shape 3, including the scalar sub function space 
W too.

Johan


On Friday April 8 2011 05:44:56 Melanie Jahny wrote:
> Question #152076 on DOLFIN changed:
> https://answers.launchpad.net/dolfin/+question/152076
> 
>     Status: Answered => Open
> 
> Melanie Jahny is still having a problem:
> Sorry, I just wanted to keep the question text brief.
> The code is
> 
> mesh = Rectangle(0,0,150,0.29, 750, 20)
> mesh.order()
> 
> # Define function spaces (P2-P1)
> V = VectorFunctionSpace(mesh, "CG", 2)
> W = FunctionSpace(mesh, "CG", 1)
> 
> # combined Function Space
> VW = V*W
> 
> (u,p) = TrialFunctions(VW)
> 
> class InitialConditions(Expression):
>     def __init__(self):
>         random.seed(2 + MPI.process_number())
>     def eval(self, values, x):
>         values[0] = 0.02
>         values[1] = 0.02
>     def value_shape(self):
>         return (2,)
> 
> 
> I tried now to use a Function for Interpolation:
> 
> u_init = InitialConditions()
> u_test = Function(V)
> u_test.interpolate(u_init)
> 
> I get an error message in eval. It works if I change the eval function
> in the InitalConditions class:
> 
> def eval(self, values, x):
>         values[0] = 0.02
> 
> But if I do this, are the two components of the vector valued function
> initialized?
> 
> And I've got another question:
> Can I define the solution of a differential equation as a Function instead
> of a TrialFunction?
> Can I use u_test now as the solution function?
> What is the difference?
> 
> Thanks for your help!!!

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