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-   -   Resistance boundary conditions (http://www.cfd-online.com/Forums/openfoam-solving/59435-resistance-boundary-conditions.html)

nzy102 September 13, 2007 21:57

Hey Guys: Has anybody here
 
Hey Guys:

Has anybody here used resistance outflow boundary condition in openfoam? Basically what it does is to keep the ratio (resistance R) bewteen pressure P and flow rate Q constant at the outlet, instead of using constant pressure or other outlet boundary conditions? Assume that the pressure on the outlet cross section is constant.

Thank you.

Ning

7islands September 14, 2007 05:03

Hi Ning, If I'm not getting w
 
Hi Ning,
If I'm not getting wrong might this thread be of any help to you? ...or not?

Takuya

nzy102 September 15, 2007 12:09

Hi Takuya: Thank you for sh
 
Hi Takuya:

Thank you for sharing your code. It is pretty close. The only difference is that I need to replace normal velocity by integral surface flow rate. The problem is when I tried to compile your code, I got some error like:

make: *** No rule to make target `/derived/normalIncidenceAcousticImpedance/normalIncidenceAcousticImpedanceFvPat chScalarField.dep', needed by `Make/linux64GccDPOpt/dependencies'. Stop.

Can you let me know why this happened? Thank you.

Ning

7islands September 17, 2007 21:22

Hi Ning, Well, there are vari
 
Hi Ning,
Well, there are various things you have to be careful about the code, at least:
  • as the posted date of the code obviously indicates, the code is to be used with OF 1.3. For newer OF versions you need to make modifications accordingly.
  • as the code was meant to be just an proof-of-cocept, it just calculates boundary p or U based on patch-internal cell-center value of the opposite variable (with the b. c. type set to zeroGradient). If you intend to make serious use of the code numerical discretization schemes must be carefully cosidered besides modification from flow velocity to flow rate.
Actually I myself no longer use nor maintain the code so you have to do above by yourself. Still, it should serve as a much better starting point compared to writing it from scratch all by yourself.

Good luck,
Takuya

nzy102 September 17, 2007 22:23

Thank you for your reply. I fi
 
Thank you for your reply. I figured the problem out and now I don't have any compilation errors. I have one more question though: can you explain the following line in your code?

operator==(2.0 * z_ * (n & Up) - *this);

It doesn't ring a bell for me. Thank you.

Ning

7islands September 19, 2007 20:14

Hi Ning, It's an #if 0'ed l
 
Hi Ning,

It's an #if 0'ed line anyway so please don't care. It's an updating equation if velocity and pressure are teken staggered in time ((*this<sub>new</sub> + *this<sub>old</sub>) / 2 = z_ * (n & Up)).

Takuya


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