Please see the link below

https://www.youtube.com/watch?v=GVSLyb7buEU

Regards

https://studentcommunity.ansys.com/thread/setting-a-rotating-boundary-in-fluent-2d/

Hello @Tianxu Yin,

This UDF is quite easy.

Define mass flow rate function. Inside the function, find inlet pressure or pressure at iso-surface very near to inlet. Use inlet boundary condition id to find the pressure of the respective wall.

You can use interpreted UDF or compiled UDF as this UDF is quite simple.

Hope you got some idea. Dont hesitate to ask if you have any doubt.

Hi Vivek Tiwari ,

Thanks for the reply.

I actually don't have experience with UDF. Do you have some templet which similar to my case, I can follow and learn?

No issue, Please share Inlet boundary ID number from fluent as shown in attached image. I will help you in writing this UDF.

Hi Vivek Tiwari ,

I'm very appreciate your help!

I've attached the boundary ID number.

Just in case if you find it's convenient to use Email. My email address is [email protected].

Thanks very much!

#include "udf.h"

DEFINE_PROFILE(inlet_mf,th,i)

{

face_t f;

cell_t c;

int ID = 5;

Thread *th;

Domain *d;

d = Get_Domain(1);

th = Lookup_Thread(d,ID);

mf_max = 20; //This is dummy value for maximum mass flow rate. Pls write the correct value

mf_1 = 20; // this is dummy value for integral of rho*u*dA

po= 20; // this is dummy value for po. Use example of inlet pressure to find this

pc = 20; //this is dummy value for pc.

begin_f_loop(f,th) //to find inlet pressure

{

F_AREA(A,f,th);

area = NV_MAG(A);

pres = F_P(f,th);

area_tot += area;

psum += pres*area;

}

end_f_loop(f,th)

pi = tsum/area_tot;

begin_f_loop(f,th)

{

if(po

Hi Tianxu Yin

Find shared code in my previous comment.

I think it will work. However, You have to find Pcr, Po, MF_max and MF_1. Use pi example to find Pcr nd Po. and calculate for MF_max and MF_1.

Hi Vivek Tiwari

Thank you very much!!!

I'll try to implement that recently.

Hi Vivek Tiwari

For the pi example, pi is calculated by using pi = tsum/area_tot. I'm wondering if 'tsum' is a typo, should it be 'psum' instead?

Regards,

Tianxu

Oh yes. pls correct.

Hi Vivek Tiwari

I just realise these three possible cases for the inlet BC can happen at the same time. That is, at some time, half of the inlet BC acts as a wall, and half of the inlet BC has non-zero mass flow rate.

I'm wondering how to define the mass flow rate of individual cell at inlet boundary? Since I guess the UDF boundary condition define the boundary as a whole, correct me if I'm wrong...

Sincerely,

Tianxu

Hi Vivek Tiwari

Thanks again for your code!

I've modified the code, it successfully compiles with Fluent, but error appeared when I initialised the solution.

Node 0: Process 3524: Received signal SIGSEGV.

================================================== ============================ ================================================== ============================

Node 1: Process 10032: Received signal SIGSEGV.

================================================== ============================ ================================================== ============================

Node 2: Process 11508: Received signal SIGSEGV.

================================================== ============================ ================================================== ============================

Node 3: Process 12336: Received signal SIGSEGV.

================================================== ============================

999999: mpt_accept: error: accept failed: No error

999999: mpt_accept: error: accept failed: No error

999999: mpt_accept: error: accept failed: No error

999999: mpt_accept: error: accept failed: No error

999999: mpt_accept: error: accept failed: No error MPI Application rank 0 exited before MPI_Finalize() with status 2 The fl process could not be started.

I've tried to solve this problem for days, but I still couldn't fix this...

I attach my code to the next post. Would you mind give me some suggestions and help me out with this?

Your help is very significant to me.

Sincerely,

Tianxu

Here is my code.

It looks fine to me. Use some monitors to while testing this UDF. Hope it will work.

Hi Vivek Tiwari

Sorry I didn't get ' Use some monitors to while testing this UDF '. What monitors do you mean?

Thanks