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Initial condition for unsteady calculation

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Old   September 30, 2008, 15:09
Default Initial condition for unsteady calculation
  #1
Jianglan
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If we are trying to simulate a flow which,despite having boundary conditions that are constant in time, still is expected to exhibit unsteady behaviour. In choosing an initial condition for the unsteady calculation, would it make sense to use the steady solution(presuming one can be found)?

Thanks
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Old   September 30, 2008, 19:26
Default Re: Initial condition for unsteady calculation
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Harish
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The flow would eventually become unsteady due to the numerical errors but depending on the problem being studied the time taken for reaching unsteadiness might be long if you use a steady solution. Try using a perturbed solution of the form

U_i=U_s+C*U_s*sin(w*x)......

where C you can use between 0.05-0.2 and w is the frequency which you can compute based on the domain size or you can impose arbitrary frequencies.

Hope this helps.
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Old   October 1, 2008, 23:58
Default Re: Initial condition for unsteady calculation
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Jianglan
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Thank you very much. I grasped the general meaning, however I GOT LOST in the Equation (the perturbed solution). Is there any book or website you may recommend? Thank you.

Kind Regards
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Old   October 2, 2008, 03:47
Default Re: Initial condition for unsteady calculation
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Harish
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There was a discussion on this topic in the context of channel flow in the current forum. search in the forum and you would find it.
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Old   October 6, 2008, 00:55
Default Re: Initial condition for unsteady calculation
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Jianglan
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Thanks Harish. ^_^
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