[enry]

Hi all...
I wrote a udf that move my mesh, and it work well on fluent 6.3.26.
When I read it on fluent 12 it doesn't work, and says:

Warning: incorrect grid motion UDF (assuming no motion)

Could anybody help me???
Thanks a lot!

[ariereath]

I am having this same problem. I downloaded a UDF for FLUENT 6 off the web and the newer version (12.0) will not read it.

Any ideas???

[zdeth]

Anyone find a solution to this yet? The udf I (assume) we're working with for the old version is something like:

#include "udf.h"

DEFINE_CG_MOTION(wave, dt, vel, omega, time, dtime)
{
vel[0]=(0.037098)*((1 - exp(-2.303*time))*7.7528*cos(7.7528*time) + ((2.303*exp(-2.303*time))*sin(7.7528*time)));
}



Anyone know what is incompatible-missing to get it working in version 12?
The UDF is meant to move a wall forward and back, like a piston.
my specific error when trying to apply the UDF to the zone is :

warning: incorrect cg motion UDF wave on zone 3 (assuming no motion)

with zone 3 being the wall that is supposed to move

Thanks
-Christopher

[enry]

Hi! I don't know how my udf didn't work on fluent 12... now is working...maybe there was an error in fluent journal... However, to this link there is an UDF that I use now on fluent 12... I hope that it could be interesting...

http://www.cfd-online.com/Forums/flu...rface-udf.html


bye.

[ariereath]

Someone mentioned to me it could have to do with the "Load" command... instead of hitting "Load", you select your source "c" files (ex: xx.c) and hit "Build" to create a new Library and then hit "Load".

I tried this, it didn't quite work for me yet but it got me a step closer.

[zdeth]

Thanks for the tips guys, I did what you said arierath, (add source code then build, then load) but I get this:
"open_udf_library: %1 is not a valid Win32 application."

I pulled these files directly out of a tutorial so I can only assume its a matter of version compatibility? (v12)

Do you know what the difference is between "compiled" and "interpreted" ? 'cause I can 'interpret' my *.c file with out the error above, but then get the "incorrect cg motion" error when trying to apply it to my wall

[ariereath]

From what I understand, you have to do this within the "Compiled" option

[enry]

most of mesh-motion-UDF can only be executed as COMPILED. In particular only DEFINE_SDOF_PROPERTIES can be executed ad interpreted or compiled udf.
You have at first to build it, and then load.
Bye.

[almostafa67]

hi everybody...
dear enry i saw that u wrote an udf for a special kind of motion,i am trying to simulate peristaltic pump and for this i need to write an udf file to rotate on of edges about z axis,i will be thanfull if u could help me with this problem.
thank you in advance..

[enry]

Hi.
I don't know anything about peristaltic pump. I have red quickly this page:

http://en.wikipedia.org/wiki/Peristaltic_pump

Do you have to simulate this type of pump? Is your domain elastic like the link suggest?
If you want to impose only a rigid body rotation of some geometry , you can use sliding interface, is simpler and is the best for this type of motion. As an example, I use sliding interface to rotate a turbine along z axis.
Regards.

[almostafa67]

hi dear enry...
I sent you 2 image of the case that i'm working on it,actually both of them are kind of peristaltic pump that i simulated them in gambit,i want to move the small circle on the edge of bigger circle,i think it needs a very simple udf to rotate the center of small circle about axis that passes through center of bigger circle,my case is a DM(dynamic mesh) case;
in fact i dont know which command in C can do this simple movement for;
Was wondering if you could help me out


i'm looking forward to ur help. ^ ^

[enry]

I think that you should create UDF describing the movement of 2 circles mathematically. Try to write a simple UDF in which you describe the rotation, like the following:

DEFINE_CG_MOTION(myudf, dt, cg_vel, cg_omega, time, dtime)
{

real omega;

omega = your value

cg_vel[0] = 0.0;
cg_vel[1] = 0.0;
cg_vel[2] = 0.0;
cg_omega[0] = 0.0;
cg_omega[1] = 0.0;
cg_omega[2] = omega;

}

Impose, to begin:
-Spring constant factor 0
-Convergence tolerance 0.0001
-Number of iteration 200
-UDF to the 2 circle;
-Deforming to the fluid around the circle

With this options fluent should move your circle adapting the mesh around them. In order to have big angle of rotation of the circle, you have to enable the re-meshing, and change spring constant factor properly. Try to move your circles with mesh motion GUI command.

I think that you will have some problem with re-meshing, because in my experience fluent is not so clever to re-mesh the domain.

Furthermore obviously you have to modify your UDF in order to have a complete rotation of the circles, and invent something that can simulate the presence and absence of the circle when they aren't in the domain.


I hope that it can help you.
Regards.

[almostafa67]

hi dear Enry...
I just modified your code and compiled but there is a problem,Fluent does not let me to set it as a motion UDF/profile (FLUENT even does not show it)
a; any idea?

[enry]

Hi,
you must compile it first. Define->User-defined->Function->Compiled. Add the .c code, build it and then load. Check if Fluent reports some errors.
After this operation you should have your motion udf in dynamic mesh zones ( if I remember well under rigid body).
bye

[almostafa67]

dear enry...
a long time since we did not correspondence
i have 2 news for you:what do u want first?the good news or the bad?
the good one:the udf worked and it displaced the small cylinder,and the bad one
cylinder has been locked in its end points;how can i tell fluent to release it and move cylinder???

[enry]

hi, I answered to the other post that you posted on another thread.
However, I don't know how cylinder could desappear arriving at the end of the semicircular domain... maybe you should "invent" a function of the cilynder describing the shape of the "desappearing cylinder"... I don't think that fluent has a funtion to do it. I think that you should try something with UDF.

[krishnaprasad]

i have a program to generate stock's second order waves. but after loading in fluent the file name is not showing in the DYNAMIC ZONE WINDOW...and an error is showing that no moving zone selected!!...

can u please help me.. i am including the udf.
thank u in adv

#include "udf.h"
#define PI 3.14159265
#define GRAV 9.81
#define H 1.5
#define D 10.0
#define T 6
#define L 20

DEFINE_PROFILE(x_velocity, thread, position)
{
real x[ND_ND];
real y;
real AA,BB,CC,DD,EE,FF,GG,LL,ZZ,K;
face_t f;
begin_f_loop(f, thread)
{
real t = RP_Get_Real("flow-time");
F_CENTROID(x,f,thread);
y = x[1];
ZZ= y - D;
K = 2*PI/L;
AA= cosh (K*(ZZ + D));
BB= cosh (K* D);
CC = sinh (K*D);
DD= cos (PI/2.0 -2.0 *PI*(t/T));
EE= cos (2.0*(PI/2.0 -2.0 *PI*(t/T)));
FF= cosh (2.0*K*D);
GG= cosh (2.0*(K*(ZZ + D)));
LL= D+(H*DD/2.0)+(PI*H*H/(8.0*L))*(BB/pow (CC,3.0))*(2.0+FF)*EE;

if (y <= D)
F_PROFILE(f,thread,position)=H/2.0*(GRAV*T/L)*AA*DD/BB+0.75*PI*PI*H*H/(L*T)*GG*EE/pow(CC,4.0);
else if (y <= LL)
F_PROFILE(f,thread,position)=H/2.0*(GRAV*T/L)*BB*DD/BB+0.75*PI*PI*H*H/(L*T)*FF*EE/pow(CC,4.0);
else
F_PROFILE(f, thread, position) = 0;
}
end_f_loop(f, thread)
}
DEFINE_PROFILE(y_velocity, thread, position)
{
real x[ND_ND];
real y;
real K,MM,NN,OO,PP,QQ,RR,SS,TT,UU,VV,WW,ZZZ;
face_t f;
begin_f_loop(f, thread)
{
real t = RP_Get_Real("flow-time");
F_CENTROID(x,f,thread);
y = x[1];
ZZZ= y - D;
K = 2*PI/L;
MM= sinh (K*(ZZZ + D));
NN= cosh (K* D);
OO= cos (PI/2.0 - (2.0 *PI* t/T));
WW= cos (2.0*(PI/2.0 -2.0 *PI*(t/T)));
VV= sin (PI/2.0 - (2.0 *PI* t/T));
QQ= sin (2.0*(PI/2.0 -2.0 *PI*(t/T)));
RR= sinh (K*D);
SS= cosh (2.0*K*D);
TT= sinh (2.0*(K*(ZZZ + D)));
UU= sinh (2.0*K*D);
PP= D+(H*OO/2.0)+(PI*H*H/(8.0*L))*(NN/pow (RR,3.0))*(2.0+SS)*WW;
if (y <= D)
F_PROFILE(f,thread,position)=H/2.0*(GRAV*T/L)*MM*VV/NN+0.75*PI*PI*H*H/(L*T)*TT*QQ/pow(RR,4.0);
else if (y <= PP)
F_PROFILE(f,thread,position)=H/2.0*(GRAV*T/L)*RR*VV/NN+0.75*PI*PI*H*H/(L*T)*UU*QQ/pow(RR,4.0);
else
F_PROFILE(f, thread, position) = 0;
}
end_f_loop(f, thread)
}