12.1.3 Time Dependent Diffusion Coefficient

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12.1.3 Time Dependent Diffusion Coefficient

For isotropic conductivity of concrete, an additional time dependency may be specified to simulate a time dependent diffusion coefficient according to

k(t) = $\displaystyle \left(\vphantom{ 1 - m }\right.$ 1 - m $\displaystyle \left.\vphantom{ 1 - m }\right)$ k₀ $\displaystyle \left(\vphantom{ \frac{t_0}{t} }\right.$ $\displaystyle {\frac{{t_0}}{{t}}}$ $\displaystyle \left.\vphantom{ \frac{t_0}{t} }\right)^{{\!n}}_{}$

(12.2)

with k₀ the conductivity as defined by CONDUC or CONDIS, m a decay factor, n an age factor, and t₀ the reference concrete age.

Dependency on time (syntax)

$\begin{figure}\centering \begin{tabbing} \texttt{'MATERI'} \\ [-1.0ex] \rule{14... ...extit{n}}$_{r}\,$ \texttt{\textit{m}}$_{r}\,$ {]} \end{tabbing} \end{figure}$

DIFPOW

specifies the parameters defining the diffusion coefficient time dependency function.

t0: is the reference concrete age t₀ (usually t₀ = 28 days).
n: is the age factor n (usually 0.4 < n < 0.8 ). (n > 0 )
m: is the decay factor m .

(file.dat)

'MATERI'
    1 CONDUC  7.0E-2
      DIFPOW  28.0    0.6     0.0

In this example, the diffusion coefficient as a function of time is based on a conductivity that is constant.

(file.dat)

'MATERI'
    1 TIME    0.      50.     360.
      CONCEN  0.1     0.9
      CONDIS  1.0E-2  7.0E-2  2.0E-1
              4.0E-2  9.0E-2  6.0E-1
      DIFPOW  28.0    0.6     0.0

In this example, the diffusion coefficient as a function of time is based on a conductivity that itself is dependent on both time and concentration.

Next: 12.2 Boundary Elements Up: 12.1 Conductivity and Capacitance Previous: 12.1.2 Variable Properties Contents Index

DIANA-9.3 User's Manual - Material Library
First ed.

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