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Acoustic Perturbation Equations (APE)

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Old   September 11, 2015, 03:14
Default Acoustic Perturbation Equations (APE)
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Sergej
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Hello everybody,

i am new at OpenFoam, but i read much theory of it and now I would like to implement the Acoustic Perturbation Equations (APE) in OpenFoam. I think it would not be very easy, so i hope that maybe somebody here have made experience with it.

Here is the relevante paper link:
http://www.sciencedirect.com/science...21999103001682

If you are a student, then it is mybe for free, if you log in with VPN of your university.

So if i get some experience with it i will share it here.
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Old   February 24, 2016, 14:50
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Hasan K.J.
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Dear Tonky,

By any chance did you have any luck in implementing APE in OpenFOAM.

Regards,
Hasan K.J
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"Real knowledge is to know the extent of one's ignorance." - Confucius
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Old   September 27, 2016, 10:20
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Hello Hasan,

after some practice with OF, I have started to work further on the implementation of APE-2 theory. But now I am facing some problems, which I am now trying to solve, also with the help of cfd-online.com.

I noticed that the equations of "APE-2" are similar to the equations of Seo and Moon in "Linearized Perturbed Compressible Equations":
http://www.cfd-online.com/Wiki/Hydro...stic_splitting

But my problem is now that i implemented the following three equations (see attached files) and I am solving them on the explicit way (diagonal solver) and the values of rho' and u' are increasing during the simulation without a limit. Now I am trying to implement them on the implicit way. Is this possible and if yes, how?

Hasan, did you have some experience with APE?
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Old   September 30, 2016, 05:44
Default how to solve coupled equations?
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Hello Foamers,

I have read many posts here in cfd-online, but could not solve my problems with the iterations with the number of zero. I implemented the three equations in the following form:

Code:
solve(fvm::ddt(rhoS)+ rhoS * (fvc::div(averageU))
==
- rho * (fvc::div(Ua))
);
Code:
solve(fvm::ddt(Ua)+ fvc::grad(averageU & Ua)
==
- fvc::grad(pa));
Code:
solve(rho*fvm::ddt(pa)- c0*c0*fvc::ddt(rhoS)
==
- rho*fvc::ddt(pS));
The problem now is that the values of Ua and rhoS are rising until the simulation is breaking down, because of to high values. In my opinion it is because the solver cannot make more then one iteration and so could not converge. Am I right? And how can I solve this PDE's the right way?
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Old   January 21, 2018, 22:20
Default Dear Tonky, Have you solved your problems?
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I'm getting in trouble with APE in OpenFOAM too...Thanks!

Quote:
Originally Posted by tonky View Post
Hello Foamers,

I have read many posts here in cfd-online, but could not solve my problems with the iterations with the number of zero. I implemented the three equations in the following form:

Code:
solve(fvm::ddt(rhoS)+ rhoS * (fvc::div(averageU))
==
- rho * (fvc::div(Ua))
);
Code:
solve(fvm::ddt(Ua)+ fvc::grad(averageU & Ua)
==
- fvc::grad(pa));
Code:
solve(rho*fvm::ddt(pa)- c0*c0*fvc::ddt(rhoS)
==
- rho*fvc::ddt(pS));
The problem now is that the values of Ua and rhoS are rising until the simulation is breaking down, because of to high values. In my opinion it is because the solver cannot make more then one iteration and so could not converge. Am I right? And how can I solve this PDE's the right way?
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