[Amir]

Originally Posted by mecamor

how I should set conditions to limit the piston with moving wall so that the piston moves

As I said before, in moving wall method you have just set a boundary condition over that! if you want it to move, use dynamic mesh instead.

[mecamor]

I modeled the cylinder come a rectangle. and also as a piston rectanble. I left a bit of space between the piston and the cylinder. bopundary conditon as I put Moving wall for the piston but still. I'm fluent again. Amir Please do you can give me more detail
thanks you

[mecamor]

Dera amir I put dynamic mesh for the piston or the fluid

[Amir]

Originally Posted by mecamor

Dera amir I put dynamic mesh for the piston or the fluid

The easiest way for you is writing a UDF for the piston and hook to to the piston and with appropriate setting in dynamic mesh panel (smoothing & re-meshing) change the fluid zone cells. it's also better to take a look over manual.

Amir

[mecamor]

Originally Posted by Amir

The easiest way for you is writing a UDF for the piston and hook to to the piston and with appropriate setting in dynamic mesh panel (smoothing & re-meshing) change the fluid zone cells. it's also better to take a look over manual.

Amir

Hi Amir
I wrote the UDF of the piston, but when compiling with C 13 or it Fluent There's an error in line 3. How I should do. thank you
Error: C:\Program Files\ANSYS Inc\v130\fluent\ntbin\win64\PISTON2.c: line 3: parse error.

How I should do. thank you
#include "udf.h"
#include "dynamesh_tools.h"
static real v_prev= 0.0;
DEFINE_CG_MOTION(piston, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
real NV_VEC (A);
real force, dv;
/* reset velocities */
NV_S (vel, =, 0.0);
NV_S (omega, =, 0.0);
if (!Data_Valid_P ())
return;
/* get the thread pointer for which this motion is defined */
t = DT_THREAD ((Dynamic_Thread *)dt);
/* compute pressure force on body by looping through all faces */
force = 0.0;
begin_f_loop (f, t)
{
F_AREA (A, f, t);
force += F_P (f, t) * NV_MAG (A);
}
end_f_loop (f, t)
/* compute change in velocity, i.e., dv= F * dt/ mass;
velocity update using explicit eulerformula */
dv= dtime* force / 50.0;
v_prev+= dv;
CX_Message ("time = %f, x_vel= %f, force = %f\n", time, v_prev, force);
/* set x-component of velocity */
vel[0] = v_prev;
}

[Amir]

Originally Posted by mecamor

Hi Amir
I wrote the UDF of the piston, but when compiling with C 13 or it Fluent There's an error in line 3. How I should do. thank you
Error: C:\Program Files\ANSYS Inc\v130\fluent\ntbin\win64\PISTON2.c: line 3: parse error.

How I should do. thank you
#include "udf.h"
#include "dynamesh_tools.h"
static real v_prev= 0.0;
DEFINE_CG_MOTION(piston, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
real NV_VEC (A);
real force, dv;
/* reset velocities */
NV_S (vel, =, 0.0);
NV_S (omega, =, 0.0);
if (!Data_Valid_P ())
return;
/* get the thread pointer for which this motion is defined */
t = DT_THREAD ((Dynamic_Thread *)dt);
/* compute pressure force on body by looping through all faces */
force = 0.0;
begin_f_loop (f, t)
{
F_AREA (A, f, t);
force += F_P (f, t) * NV_MAG (A);
}
end_f_loop (f, t)
/* compute change in velocity, i.e., dv= F * dt/ mass;
velocity update using explicit eulerformula */
dv= dtime* force / 50.0;
v_prev+= dv;
CX_Message ("time = %f, x_vel= %f, force = %f\n", time, v_prev, force);
/* set x-component of velocity */
vel[0] = v_prev;
}

Hi,
It doesn't have any error while compiling; try VC++ instead.

[mecamor]

Originally Posted by Amir

Hi,
It doesn't have any error while compiling; try VC++ instead.

Dear amir Whene I compil in fluent I have erro

[AlbertoP]

Hi,

follow this: http://www.cfd-online.com/Wiki/Fluen...with_Fluent_13

You will find how to set Visual C++ to compile UDF, and how to open Fluent depending on the OS you have (32 or 64 bit).

Regards

[AlbertoP]

Hi Amir,

sorry for my delay.
Just wanted to thank you for your support.
Now it's working...but you need to hook UDF only to the grid you want to move. Only in that way I don't get a negative volumes error.

Regards
Alberto

[mecamor]

hello
I work with windows 7. how to build the library udf. and when I compile my udf fluent that he lacks nmake.

[AlbertoP]

Hi,

as I said above, you only need to follow the instructions given on that answer (http://www.cfd-online.com/Wiki/Fluen...with_Fluent_13). I had the same problem (lack of nmake). And I use Win 7 as well.

Mind to open Fluent from SDK command prompt.
regards

[Vidit Sharma]

hi,

I am trying to move a 2d cylinder in y direction by using UDF:-
# include "udf.h"
# include "dynamesh_tools.h"
DEFINE_CG_MOTION(pump,dt,cg_vel,cg_omega,time,dtim e)
{
Thread *t;
real freq_t;
NV_S(cg_vel,=,0.0);

if(!Data_Valid_P())
return;
freq_t = 0.01;
t= DT_THREAD((Dynamic_Thread*)dt);
cg_vel[0] = 0.0;
cg_vel[1] = freq_t;

}

But I am having a problem while compiling it in Visual Studio Command Prompt. While executing nmake command to compile an error is appearing which is saying NMAKE : fatal error U1077: "sed" :return code '0X1'

can anybody tell how to eliminate this error????

Thank You

Regards

Vidit Sharma

[samcfd]

Hi everyone,

I want some help regarding an issue i'm facing. I need to write a UDF for rotating an O Grid. To be precise we can rotate using GUI MESH - ROTATE and solve it. But i need to do the same using an UDF. For example i need to rotate the whole domain by 8 deg I give that value in the UDF and the grid gets rotated. Can some1 help me out regarding this.

Thanks in advance,
sam.

[shri.hade]

Originally Posted by Amir

Hi,
if you use moving wall, you have just set a boundary condition over that and it wouldn't move. To achieve you purpose, you have to use dynamic mesh instead which as I know, there is special kind for moving piston in cylinder.

Regards,

Amir

Hi Amir,
I am working on CFD analysis of a vertical axis wind turbine, in that i need to find RPM of a turbine using fluent.
for this i need to write a UDF but i am totaly unaware of the UDF concept will you please guide me how to write a UDF for this case

[Ahmed Saeed Mansour]

Hello, I wanna write a code to make a variable inlet speed and variable rotating speed (based on the variable velocity) for a rotor in fluent..What should I do?
Thanks

[Jawad Zakir]

Originally Posted by Amir

Dear Alberto,
It seems that your settings are correct and I don't think that the problem origins from walls created over interfaces. I have 2 suggestions:
1) to make sure about your UDF, hook it to the whole domain and check whether it works or not.
2) after you have changed dynamic mesh settings, it's better to write your case and read it again and then see grid motion panel.
if you don't have any progress, send it to my E-mail.

Amir

I am facing the same kind of problem. how can i contact you over the email?

[SadeghRaji]

Hello every one!

I want to write a code that rotates a body in a room with the following specifications.

When the time is between this interval 👇

1 <t <2.57 seconds

The angular velocity (w) should be 👇👇

w = 1 (rad / s)

And When time is out of range. the angular velocity is zero.

And the body rotates 90 degrees.

Visual Studio is paired with Fluent and has no problems.

Now the problem is how do I write this code?

[AlexanderZ]

Ansys Fluent Customization manual

look for DEFINE_ZONE_MOTION macro

[Ahmed Saeed Mansour]

Originally Posted by SadeghRaji

Hello every one!

I want to write a code that rotates a body in a room with the following specifications.

When the time is between this interval 👇

1 <t <2.57 seconds

The angular velocity (w) should be 👇👇

w = 1 (rad / s)

And When time is out of range. the angular velocity is zero.

And the body rotates 90 degrees.

Visual Studio is paired with Fluent and has no problems.

Now the problem is how do I write this code?

Hello, check out this link:

https://www.researchgate.net/post/Ho...s_through_time

Also, I found that typing the code using else if not easy, I prepared three UDF files, each one contained one equation for each motion. At the required time, I stop the simulation and insert the other UDF until I reach the next required time and I insert the new UDF and it worked. However, you may find the other solutions better for your case.
Thanks