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How to introduce a scalar as C(t) = f(C(t-1))

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Old   February 23, 2006, 00:13
Default How to introduce a scalar as C(t) = f(C(t-1))
  #1
Mahad
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I'm trying to model a scalar distribution in a reactor. The problem is that I need to intrudce an expression for the scalar flux through one of the walls of the reactor. I need the flux to accounts for the value of the scalar in the reactor one time step before it determine the new value; say C(t) = A*C(t-1)* exp(-kt); where A and k are constants.

Hope you guys can help with that.

Thanks
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Old   February 23, 2006, 13:21
Default Re: How to introduce a scalar as C(t) = f(C(t-1))
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Robin
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Hi Mahad,

In a steady state calculation, if you make the scalar a function of itself, the value it will use will come from the previous timestep. Similarly, if you use any of the integral functions on boundaries in your expressions, the results are returned for the values at the previous timestep.

Regards, Robin
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Old   February 23, 2006, 13:58
Default Re: How to introduce a scalar as C(t) = f(C(t-1))
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Mahad
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Thanks a lot Robin. But what about transient simulations.
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Old   February 23, 2006, 16:12
Default Re: How to introduce a scalar as C(t) = f(C(t-1))
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Mahad
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The CFX-Pre didn't accept self referencing of the function (using the expression option) even for steady state simulations. Do you know how to get though that?!
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Old   February 23, 2006, 16:30
Default Re: How to introduce a scalar as C(t) = f(C(t-1))
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Robin
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Create an algebraic additional variable equal to your variable. If you're using this in a transient simulation, I don't think what I suggested applies as it will end up using the value from the previous coefficient loop.

-Robin
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