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Old   April 30, 2007, 15:54
Default Stabilizing Transient Source term
  #1
CFDtoy
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I am solving a energy transport equation of the form

drhoH/dt + del.(rho V H) = -dP/dt+...+.

in a collocated arrangement. I see that as the simulation progresses, the sources due to dp/dt is highly unstable.

How can I stabilize my computation? The computation is for an incompressible flow but with heat transfer.

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CFDtoy
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Old   May 1, 2007, 10:37
Default Re: Stabilizing Transient Source term
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Harish
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What kind of time-marching scheme do you use?.For multi-stage R-K it might be unclear how to discretize dp/dt on RHS.
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Old   May 1, 2007, 11:16
Default Re: Stabilizing Transient Source term
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CFDtoy
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I am using a simple backward euler (implicit for stability!) Does any time splitting work?

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Old   May 1, 2007, 12:02
Default Re: Stabilizing Transient Source term
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Harish
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The stability analysis is based on linearized theories and hence you cannot necessarily guarantee stability for non linear problems.Did you check if explicit time marching worked for this particular case?
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Old   May 1, 2007, 18:59
Default Re: Stabilizing Transient Source term
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CFDtoy
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explicit time stepping posed a lot of problems..since i hd problems in converging them.

normally when the source terms are not functions of the flw variables and cause such kind of stability problem..is there a way to reduce their propagation !>!? I am not aware of time splitting schmes for these purposes?

anythin related?

Thanks for your cmments harish.

-- CFDtoy
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Old   May 1, 2007, 20:26
Default Re: Stabilizing Transient Source term
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Harish
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I have never come across anything either.Is there any reason for using the equation for enthalpy instead of total energy or internal energy.Those equations do not have a time dependent pressure term and your implicit euler implementation might be easier.
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Old   May 2, 2007, 08:27
Default Re: Stabilizing Transient Source term
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CFDtoy
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In case of total enthalpy, you do require the dp/dt term on the RHS. Also, finding temp using total enthalpy seemed easier.

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Old   May 2, 2007, 09:15
Default Re: Stabilizing Transient Source term
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Harish
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I think it would be the same even if you use the equation for internal energy.
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