On 01/12/08 09:33 AM, Garth N. Wells wrote:
>
>
> Bartosz Sawicki wrote:
>> On 01/12/08 09:07 AM, Garth N. Wells wrote:
>>>
>>> Bartosz Sawicki wrote:
>>>> Hi all,
>>>>
>>>> I can't find anything in the manuals, any example in the demo
>>>> directory and even google is silent like a grave, when asked for
>>>> "anisotropy site:fenics.org".
>>>> Does it mean that anisotropy is not supported by FEniCS?
>>>>
>>> Can you be more specific on what you have in mind?
>>
>> My question is, if anyone has already tried to solve any anisotropic
>> problem with fenics?
>>
>> One of the problems, which come to my mind is that for anisotropic
>> material I need at tensor function for material property. Can FFC
>> handle this?
>>
>
> Just define the equation you want to solve and try compiling it with
> FFC. For an anisotropic solid, part of this will involve defining the
> constitutive model. The DOLFIN library shouldn't need to be (nor should
> it be) aware of the details of the constitutive model.
Yes, I know that, but there is a problem with anisotropic material
property which is in general case described by tensor.
Let's look on example. Simple Poisson equation form:
element = FiniteElement("Lagrange", "tetrahedron", 1)
v = TestFunction(element)
u = TrialFunction(element)
f = Function(element)
g = Function(element)
k = Constant("tetrahedron")
a = k*dot(grad(v), grad(u))*dx
L = v*f*dx + v*g*ds
In case of anisotropy, k (material property) shouldn't be "scalar
constant", but rather "tensor constant" over the element.
For Poisson I can manage with "vector constant", but that's definitely
not a general approach:
k = VectorConstant("tetrahedron")
a = (k[0]*D(v,0)*D(u,0) + k[1]*D(v,1)*D(u,1) + k[2]*D(v,2)*D(u,2))*dx
How would you advice to describe tensor function or tensor constant in
the form? Is it possible?
BArtek
>
> Garth
>
>> BArtek
>>
>>
>>> Garth
>>>
>>>> Strange, this seams to be quite easy to develop. Or maybe just no
>>>> one needed that feature so far.
>>>>
>>>> BArtek
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>>>
>>
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>
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