The solution behaves as expected when I define Q as a function, but in
the other case there seems to be some kind of instability and I get a
very strange result.

Anna.

On 30/09/15 15:28, Lawrence Mitchell wrote:
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> On 30/09/15 15:19, Anna Kalogirou wrote:
>> Dear all,
>>
>> I have a very simple, yet not so obvious - to me at least -
>> question:
>>
>> If I define an expression which does not depend on space variables,
>> for example
>>
>> Q_expr = Expression("A*sin(2*pi*F*t)", t=t, A=A, F=F)
>> Q.interpolate(Q_expr)
>>
>> shouldn't this be equivalent to just writing Q as a scalar,
>>
>> Q = A*sin(2*pi*F*t) ?
>>
>> This quantity Q is then used in a weak form to multiply the test
>> function v on a boundary, e.g. Q*v*ds_v(1).
>>
>> I get different results for the two cases. Clearly, in the 1st case
>> Q is a function while in the 2nd case it is a scalar, but I don't
>> see why this would give different results. I might be missing
>> something obvious here...
> These ought to be equivalent.  But can you describe how they are
> different?
>
>
> Lawrence.
>
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--

  Dr Anna Kalogirou
  Research Fellow
  School of Mathematics
  University of Leeds

  http://www1.maths.leeds.ac.uk/~matak/

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