[raviramesh10]

Hello everyone!

I am currently working on a project which involves the simulation of Colgate toothpaste on a vibrating membrane in ANSYS Fluent. I would require the input of the vibrating membrane as its velocity, which is a sinusoidal function of space and time.

For this, I have written a UDF, which isn't working due to errors in the code. Could someone please help me in this regard? This is really urgent.

The UDF is as follows:
#include "udf.h"
#include "dynamesh_tools.h"
#define pi 3.1416
DEFINE_GEOM(plane,domain,dt,position)
{
position[1]=0.001;
}
DEFINE_GRID_MOTION(inlet_y_velocity,d,dt,time,dtim e)
{
Thread *t;
real y[ND_ND];
real x_c;
face_t f;
real v;
Node *w;
int n;
real sign;
SET_DEFORMING_THREAD_FLAG(THREAD_TO(t));

sign=.015*cos((pi*x_c)/.08);
begin_f_loop(f,t)
{
f_node_loop(f,t,n)
{
w = F_NODE(f,t,n);
if (NODE_X(v)>0 && NODE_X(v)<0.08 && NODE_Y(v)==0 && NODE_POS_NEED_UPDATE(v))
{
NODE_POS_UPDATED(v);
v=sign*sin(2*pi*120*time);
}
end_f_loop(f,t)
}
}
}

[Светлана]

Hi,

I've not done mesh movement before, but here is a few uneducated suggestions:

1. What errors do you get? They usually help to identify the problem.
2. You seem to have a typo as I highlighted below.
3. Try to simplify your problem - reduce it to something meaningless but functional. For example, specify a zero mesh motion value and observe that the mesh is not moving; specify a constant non-zero value and observe how the mesh moves.


#include "udf.h"
#include "dynamesh_tools.h"
#define pi 3.1416
DEFINE_GEOM(plane,domain,dt,position)
{
position[1]=0.001;
}
DEFINE_GRID_MOTION(inlet_y_velocity,d,dt,time,dtim e)
// remove the space, it should be 'dtime' ?
{
Thread *t;
real y[ND_ND];
real x_c;
face_t f;
real v;
Node *w;
int n;
real sign;
SET_DEFORMING_THREAD_FLAG(THREAD_TO(t));

sign=0.015*cos((pi*x_c)/.08); // I added '0' just in case '0.015' is better than .015
begin_f_loop(f,t)
{
f_node_loop(f,t,n)
{
w = F_NODE(f,t,n);
if (NODE_X(v)>0 && NODE_X(v)<0.08 && NODE_Y(v)==0 && NODE_POS_NEED_UPDATE(v))
{
NODE_POS_UPDATED(v);
v=sign*sin(2*pi*120*time);

// The example from documentation has this stuff, maybe you should add it?
// NV_VV (rvec, =, NODE_COORD (v), -, origin);
//NV_CROSS (dx, omega, rvec);
//NV_S (dx, *=, dtime); //NV_V (NODE_COORD (v), +=, dx}
end_f_loop(f,t)
}
}
}

[raviramesh10]

Dear Svetlana,

Thank you for your reply. I have already made the necessary changes to the code in order to obtain the desired motion of the vibrating membrane. Thank you for your help.