UDF code(ask for help)
 

I am struggled with UDF, now I suppose to define the inlet velocity as below, but the code has some error, could you please help me out and check what is wrong about my code?

I appreciate it.
the equation is as below:

V(x,y,t)=15.2*((2*x/0.00625)^8-1)+0.076*sin(0.8*pi*t)+0.076*sin(6*y/0.00625)
#include "udf.h"

DEFINE_PROFILE(velocity_profile,t,i)
{
int ts;
real x[ND_ND]; /* this will hold the position vector */
real y;
face_t f;

ts = N_TIME; /*you can calculate real time from time step obtained here*/

begin_f_loop(f,t)
{
F_CENTROID(pos,f,t);
x = pos[0];
y = pos[1];
F_PROFILE(f,t,i) =-{1-(2*x/0.00625)^8 }*15.2+0.076*sin(0.8*π*t)+0.076*sin(6*y/0.00625);
}
end_f_loop(f,t)
}

There are some mistakes here:
Where is pos specified?

Try this and let me know how it works.
real pos[ND_ND]; /* this will hold the position vector */
real x,y;

Always run these over multiple time steps (even without converging) to ensure that the boundary condition is behaving as you intend.

The N_TIME macro only returns the current time step in you case it may be worth considering CURRENT_TIME instead (time independent to the time-step size), see:
http://hpce.iitm.ac.in/website/Manua...df/node105.htm

replace t by ts in the velocity profile function (t is the thread)

Hi,
 

Hi there,
Thank you for your note.
I fixed my code, but it is still not working for me...I got mad...Please help me out.
The code is as below:
#include "udf.h"

DEFINE_PROFILE(unsteady_velocity,thread,index)
{
real x [ND_ND];
face_t f;
begin_f_loop(f, f_thread)
{
F_CENTROID (x, f, t);
x=pos[1];
real t=RP_Get_Real("flow time");
F_PROFILE(f,thread,position) =-(1-(2*x/0.00625)^8)*15.2+0.076*sin(0.8*3.1415926*t);
}
end_f_loop(f, f_thread)
}

Error: D:\\Tem/udf.h: line 4: parse error.

cpp -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/multiport/src" -I. -DUDF
ONFIG_H="<C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/udfconfig-node0.h>" "C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/New Text Document (3).c.0.c"
Error: C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/New Text Document (3).c.0.c: line 7: f_thread: undeclared variable

The code with no compilation error :

#include "udf.h"

DEFINE_PROFILE(unsteady_velocity,thread,index)
{
real pos [ND_ND];
real x, t;
face_t f;
begin_f_loop(f, thread)
{
F_CENTROID (pos, f, thread);
x=pos[1];
t=RP_Get_Real("flow time");
F_PROFILE(f,thread,index) =-(1-pow(2*x/0.00625,8))*15.2+0.076*sin(0.8*3.1415926*t);
}
end_f_loop(f, thread)
}

Thank you for your note.
 

Hi, I tried your revised code, I supposed to read it in FLUENT, but I still got error, I don`t know why. What should I do when I hook this code with FLUENT?
p.s. Can we talk on skype?
pps. I am using Ansys 14.0, do you think the version of FLUENT is the problem?
ppps. Is there any space here (pos, f, thread);?(f, thread)?
(pos,f,thread);?(f,thread)? Which one is correct?

I am looking forward to your reply.
Kind regards

It looks like you have extra spaces this might be the problem:

Try changing these!

real pos [ND_ND]; => real pos[ND_ND];
F_CENTROID (pos, f, thread); => F_CENTROID(pos, f, thread);

Thank you for your note.
 

Hi, thank you both of you.

I still got an error which is attached below...What does it mean?


cpp -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/multiport/src" -I. -DUDF
ONFIG_H="<udfconfig-host.h>" "D:\Tem\u.c"
cpp -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/multiport/src" -I. -DUDF
ONFIG_H="<C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/udfconfig-node0.h>" "C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/u.c.0.c"

I don't have any errors. This is the compilation commands.

As laurentb says the output you have included does not mention either warnings or errors. Is this all of the message? It may well have compiled correctly.

What should I do?
 

mmmmm...
Thanks alot.
but I don`t know why I could not read it in FLUENT.
first, I saved it as .c file
second, in FLUENT I used define-user defined-functions-interpreted

and then I got this
cpp -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/multiport/src" -I. -DUDF
ONFIG_H="<C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/udfconfig-node0.h>" "C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/u.c.0.c"

The message you showed is not an error! This is just the compilation sequence. This was fine for me but had problems when I was applying it as a boundary condition.
I tried this and it seemed to work fine:

#include "udf.h"

DEFINE_PROFILE(unsteady_velocity,thread,index)
{
real pos[ND_ND];
real x, t;
face_t f;
begin_f_loop(f, thread)
{
F_CENTROID(pos, f, thread);
x=pos[1];
t=CURRENT_TIME;
F_PROFILE(f,thread,index) =-(1-pow(2*x/0.00625,8))*15.2+0.076*sin(0.8*3.1415926*t);
}
end_f_loop(f, thread)
}

Thank you for your note.
I tried this code, and I got new information...

cpp -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/multiport/src" -I. -DUDF
ONFIG_H="<udfconfig-host.h>" "D:\Tem\example.c"
Error: D:\\Tem\\example.c: line 2: D:\\Tem\\example.c:1: `#include' expects "FILENAME" or <FILENAME>
parse error.
999999 (..\src\mpsystem.c@1173): mpt_read: failed: errno = 10054
999999: mpt_read: error: read failed trying to read 4 bytes: No such file or directory
MPI Application rank 0 exited before MPI_Finalize() with status -1073741819
The Parallel FLUENT process could not be started.

what should I do?

You will have to debug this problem:
1) try it in serial (1 cpu)
2) try without the t=CURRENT_TIME; use t =0; instead.

These will help to narrow down the problem.

I'm not sure what happened earlier when you had problems, can you explain it further? the message "cpp -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/cortex/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/client/src" -I"C:\PROGRA~1\ANSYSI~1\v140\fluent\fluent14.0.0/multiport/src" -I. -DUDF
ONFIG_H="<C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/udfconfig-node0.h>" "C:/DOCUME~1/lzhuowei/LOCALS~1/Temp/u.c.0.c"" seems fine to me (not an error, just normal output). Did you have problems when you hooked it as a boundary condition or where did the error occur?

Hi, I appreciate both of you.
Finally the code is working properly. I am using serial instead of parallel, and also I read the udf in case rather than data and case. So it works now. It seems that there is no problem with the code. It is hooked with FLUENT, I could read this velocity in boundary condition.

Please keep contacting with me, I hope you can help me again in the near future, I am a beginner of UDF, I need you :)
kind regards
zhuowei

Hi, I appreciate both of you.
Now I am trying to plot the velocity profile in FLUENT, this work will be done if I can see a sinusoidal curve the same as what the math function describes, thanks a lot.

Unfortunately, I couldn't see the sine curve...oh my god... May I ask that how can I plot the velocity changing with time?

Usually I just can plot the velocity changing with position…

kind regards
zhuowei

You can set up a monitor at the inlet. Set it as the area weighted average velocity or just display the volume flow rate and see how it changes as time progresses (display as time-step not iteration).
For this you don't need a converged solution you just want to check what condition you have applied at the boundary so one iteration per time step is fine.

Hi Daniel,
Thank you for your note.
I did what you told me, but I got a message that "cx-xy-plot-files: No data points in range." I used auto range.
I look forward to your reply.
Many thanks
Zhuowei

Hi, I got another problem.
I have had the code, and it also could be read into FLUENT. Now I want to verify it in C++, I want to see the sin curve in c++, but unfortunately, in c++ I got some errors as below:what is the problem?
How can I fix them?

the system cannot find the path specified
1>------ Build started: Project: 01, Configuration: Debug Win32 ------
1>Compiling...
1>01.cpp
1>d:\tem\01\01\01.cpp(6) : error C2065: 'cout' : undeclared identifier
1>d:\tem\01\01\01.cpp(6) : error C2065: 'endl' : undeclared identifier
1>Build log was saved at "file://d:\Tem\01\01\Debug\BuildLog.htm"
1>01 - 2 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========