# star-cd capabilities

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 November 12, 2008, 12:09 star-cd capabilities #1 Ahmed Guest   Posts: n/a I am interested in running acoustic simulations. I wanted to check with you guys if star-cd has the capability to do the following: 1) Can we impose a time varying boundary condition at the inlet. 2) Can we impose random fluctuations (synthetic turbulence) at the inlet for a LES case. 3) Does star-cd has an option for non-reflective boundary (to prevent acoustic waves to reflect back in domain) 4) Can we run periodic/cyclic simulation for compressible flow Thanks in advance for your answer.

 November 13, 2008, 03:59 Re: star-cd capabilities #2 jimmer Guest   Posts: n/a For subquestion 1 the answer is yes. You can make a table for linear changes. If your velocity lets say is a wave then you can use subroutine bcdefi.f. The indepedent time variable is TIME while x,y,z are X,Y,Z respectively...

 November 13, 2008, 06:24 Re: star-cd capabilities #3 Ahmed Guest   Posts: n/a But making a table for lets say half a million time steps is a lot of work. Is there a not a quicker way to do that. Thank you

 November 13, 2008, 09:43 Re: star-cd capabilities #4 Anton Lyaskin Guest   Posts: n/a 1) Yes, and if you don't want to mess up with tables, you can use user subroutine 2) Not sure (I'm not the LES specialist and never tried it) 3) Yes, there are Transient Wave boundaries and Riemann boundaries 4) Didn't understand quiet well what you mean. You can run transient (i.e. unsteady) simulation. If the flow is cyclic in nature, than after some time of calculation your solution will establish cyclic behavior.

 November 13, 2008, 10:18 Re: star-cd capabilities #5 Ahmed Guest   Posts: n/a Thank you Anton. Regarding point 4, I meant cyclic boundary condition. In LES people often use periodic/cyclic boundary to generate turbulence in domain. I am sure star-cd would have periodic/cylic boundary. But can we use it with compressible flow. CFX would not allow that whereas some other codes allow it.

 November 14, 2008, 02:03 Re: star-cd capabilities #6 mactonald Guest   Posts: n/a I have no experience of using cylic boundary with compressible flow, but I think this combination will not give very precise result, I mean it is not so reasonable.

 November 14, 2008, 07:01 Re: star-cd capabilities #7 Ahmed Guest   Posts: n/a And why do you think that is so mactonald?

 November 17, 2008, 08:59 Re: star-cd capabilities #8 Anton Lyaskin Guest   Posts: n/a Ok, now I've got it. Yes, there are cyclic boundaries in Star-CD and they work fine in the compressible flow. And what you need, I guess, is the variant which is called "partial cyclic" in Star-CD, which allows a pressure drop between boundary pairs.

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