[xab]

Hi guys,

I am working on a simulation of a gear rotating inside a tank filled with oil and air just like the attached image. During the simulation I would like to store the moment needed to rotate the gear so I wrote the Compute_Force_And_Moment macro inside my UDF. I would also like to monitor this moment during the simulation so I tried with an UDM but I didn't get reasonable results. I am not really used to work with UDF's so I think it is a problem of the script. Here is the code I am using for the UDF.

#include "udf.h"
DEFINE_CG_MOTION(gear, dt, vel, omega, time, dtime)
{
Domain *domain;
Thread *t;
real x_cg[3],force[3], moment[3];
face_t f;
domain = Get_Domain(1);
t =Lookup_Thread (domain, 5);
omega[2]=100.0;
x_cg[0]=0;
x_cg[1]=0;
x_cg[2]=0;
Compute_Force_And_Moment(domain, t, x_cg, force, moment, TRUE);
begin_c_loop(f,t)
{
F_UDMI(f,t,0)=moment[2];
}
end_c_loop(f,t)
Message ("momento %g \n", moment[2]);
}

I am now trying to simulate the same problem without the VOF model (just with one fluid) to make easier the problem.

Any suggestion?
Thank you in advance, any help would be apreciated.
Xabi

[xab]

By the way, here is the contour of the UDM after few time steps.

[twcp0104]

You might try writing a file... like a text file... if you separate the values by "\t", it gets in excel pretty easily... I mean like:

FILE *data;
data=fopen("C:\randomAddress\data.txt",w+);
fprintf(data,"%g\t%g\t%g\t%g\t%.5g\t",time,x,y,z,m oment);
fclose(data);


What do you think? would that work?

You could also have a message in the log mid-simulation, if you just want to monitor the moment:

DEFINE_EXECUTE_AT_END(print_log)
{
Message("\n****time: %g\tx: %g\ty: %g\tz: %g\tmoment: %.5g\t",time, x,y,z,moment);

}

[xab]

First of all, thank you for your replay.

Yes I think it would work but I also would like to be able to plot it and understand how UDMs work. This model it is just a first attempt to familiarize with this kind of simulation (VOF & UDFs) afterwards, I would like to simulate other things such as losses inside a gearbox and others.

I have read in another thread some info about the pointers to the different domains (cell and face) that it might enlighten me a little about using UDM. I'll work a little on that and update the info in case it could be helpful for somebody else.

[xab]

Hi again,
Finally I have some results on my simulation. I was using wrong the domain ID and the boundary ID. This is the script that I am using now and it is working.

#include "udf.h"


DEFINE_CG_MOTION(gear, dt, vel, omega, time, dtime)

{

Domain *domain;

Thread *t;
Thread *tc;
real x_cg[3],force[3], moment[3];
cell_t c;

domain = Get_Domain(1);
t =Lookup_Thread (domain, 5);

tc=Lookup_Thread (domain, 1);

omega[2]=100.0;

x_cg[0]=0;
x_cg[1]=0;
x_cg[2]=0;
Compute_Force_And_Moment(domain, t, x_cg, force, moment, TRUE);


thread_loop_c(tc,domain)
{
begin_c_loop(c,tc)
{
C_UDMI(c,tc,0)=moment[2];
}
end_c_loop(c,tc)
}



Message ("momento %g \n", moment[2]);
}

Hope this would help someone