CG Motion UDF Problem
 

Hello World!

I have been working in the past few days trying to understand UDFs but i think i've reached a dead end...

This is what i'm trying to do:

I'm just trying to simulate the flow around a body wich is moving up and down with a sinusoidal law of motion. To do this i have written my UDF just as is shown below:

#include "udf.h"

DEFINE_CG_MOTION(object_mov, dt, vel, omega, time, dtime)
{
real a, w, pi;

pi = 3.1415;

/* define motion variables */
a = 0.05; /* 0.05m movement amplitude */
w = 2 * pi * 2; /* 2Hz frequency */

/* define object movement law */
vel[0] = 0;
vel[1] = -a * w * sin(w*time);
vel[2] = 0;
}

I have no problem interpreting this UDF into Fluent. However, when defining the dynamic zone the following warning appears:

"Warning: incorrect cg motion UDF wing on zone 4 (assuming no motion)"

Do you have any clue why could this be? is my UDF correctly written?
Looking forward to your answer.
Thanks!

Just to say that I have solved the problem: CG motion macro only works when compiled!!

Hi,
your missing a math header, try using these:

#include "udf.h"
#include "stdio.h"
#include "stdlib.h"
#include "math.h"
#include "dynamesh_tools.h"
#include "storage.h"

In addition, define an intermediate (i.e. "real v = 0") variable for the motion:

v = -a * w * sin(w*time);
vel[1] = v;

hopefully it will solve your problem...

How do you fix it? I have this problem but I can't fix it! Can you help me?

udf for flapping motion in hover
 

I cant write udf code for flapping motion in hover, help me, im so confused

do it with solidworks flow simulation.

J

Hi, Define CG Motion can only be compiled not interpreted. Please try compiling the UDF rather :)

hi
I am the student of fluid mechanics and now I am studying on fluid project. The subject of my project is about blade turbine that Oil radially impacts to the turbine blades by a nozzle, causing the turbine to spin. I have a problem in modeling of turbine that I don’t know how to obtain moment of inertia of blade and fluid and how to relate this challenge to the Cg motion until I can model this turbine in fluent software. Please help me
Thank for your attention

Dynamic mesh flapping wing - Interface problem
 

Hi everyone,

I am simulating flapping wing of aerofoil. I have created three zones, zone 1, 2 and 3. Zone 1 has aerofoil with structured mesh around the aerofoil. Zone 2 and 3 has unstructured gird. My problem is I have properly followed all the steps. But I am not able to achieve what I want. Because the shadow of the interface is taking as wall and is not moving along with the domain. Kindly someone help in sorting out this issue. I have attached my UDF alos. Please have a look. Thank you so much

https://drive.google.com/file/d/0B7L...ew?usp=sharing
https://drive.google.com/file/d/0B7L...ew?usp=sharing

CG_Motion udf problem
 

Dear Experts,

I am trying to do a moving mesh for a body which is moving up and down. To do this I have written below UDF:

#include "udf.h"

static real velx = 0.0;

DEFINE_CG_MOTION(box,dt,vel,omega,time,dtime)
{
NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);

velx = 0.05 * sin(3.1415927 * time / 10.);
Message ("time = %f, vel[0] =%f\n", time, vel[0]);
}

during compile i have face below error mentioned below:


Error: The UDF library you are trying to load (D:\MR Damper\CG Motion\Moving Mesh_files\dp0\FFF\Fluent\libudf) is not compiled for 2d on the current platform (win64).

The system cannot find the file specified.

D:\MR Damper\CG Motion\Moving Mesh_files\dp0\FFF\Fluent\D:\MR Damper\CG Motion\Moving Mesh_files\dp0\FFF\Fluent\libudf\win64\2d\libudf.d ll


How can I solve this problem? looking forward to your answer.
Thanks

Honestly, if you can do it in star ccm+

Ansys suck where moving geometries and large displacements are needed...

push BUILD button to compile, not load

best regards

I have an issue running my UDF
 

Attachment 73214

Attachment 73215

Attachment 73216

Hello everyone, I'm trying to get my train to move but no matter what I try, I'm not able to compile the files. I'm not sure if its the file having issues or my settings are the problem. I hope someone could shed some light on this for me.

Thanks:)

read error log

The program is wrong, even I have also stuck with the same problem.

I also get the same warning with you. However, when I try to compile my UDF, it is said that libudf does not exist. Did you get any error something like this?

unload all UDF folders via udf manager,
make any changes in source file you are going to compile
compile

May you help me with my second question in this forum? I am new in this forum and try to get help. I think there are not enough people seeing my post. I don't know why.

Thank you so much