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Jianglan September 30, 2008 14:09

Initial condition for unsteady calculation
 
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

Harish September 30, 2008 18:26

Re: Initial condition for unsteady calculation
 
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.

Jianglan October 1, 2008 22:58

Re: Initial condition for unsteady calculation
 
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

Harish October 2, 2008 02:47

Re: Initial condition for unsteady calculation
 
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.

Jianglan October 5, 2008 23:55

Re: Initial condition for unsteady calculation
 
Thanks Harish. ^_^


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