[nzy102]

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]

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

Takuya

[nzy102]

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]

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]

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]

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_new + *this_old) / 2 = z_ * (n & Up)).

Takuya

[sitajeje]

Hallo Ning,

I want to build the same boundary condition as you did in 2007: the outlet pressure is dependent on the flow rate. I wonder whether you have solved your problem? I would appreciate if you could give me some hints how to program this boundary condition.

Thank you very much!

sitajeje

[sitajeje]

Hello Takuya,

I downloaded your file normalIncidenceAcousticImpedance-20070112.tar.gz, but it turns out to be a .unk file, and I cannot unzip it. I would appreciate greatly if you could share your file again. Thank you very much in advance!

Best regards,

sitajeje

[pvpnrao]

https://www.cfd-online.com/Forums/members/sitajeje.html


This is a very late response. Just posting for the community benefit

Assuming the OS is Linux/ubuntu

Just download the (.unk) file. Rename the file with .tar extension and the just untar it using the command


tar -xvf normalIncidenceAcousticImpedance-20070112_tar-3659.tar


I am posing a .zip file of the same folder. This can be easily opened using the command


unzip normalIncidenceAcousticImpedance.zip