The concentration is approximated over the finite element as follows:
(9–8) |
where:
{N} = element shape functions
{Ce} = nodal concentration vector (input/output as CONC)
The application of the variational principle and finite element approximation Equation 9–8 to Equation 9–6 produces the matrix equation as:
(9–9) |
where:
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vol = element volume |
S = element surface |
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The finite element Equation 9–9 is unsymmetric.
To keep the equation symmetric, the transport effects can be applied as a load vector by setting KEYOPT(2) = 1 for the diffusion elements
(PLANE238, SOLID239,
SOLID240). Using this option activates a nonlinear solution, and at
least two iterations are required to achieve a response to the transport effects.