[Kevin_Liu]

Here I want to calculate the node value from neighbor cell or face by UDF. So that I can use this varible to move the grid.
[Below is my code.] I'm trying to move the node by location of face center. I save the displacement to N_UDMI. However, in parallel model, for nodes on partition boundary, N_UDMI will have different value because begin_f_loop looped different face, which will lead to separation of nodes as shown in the figure. I need a same N_UDMI for nodes on partition boundaries. For phase changing problem, it should be averaged temperature of neighbor faces.
Is there any macro can do this ?



#include "udf.h"
#include "para.h"
#include "sg.h"
#include "mem.h"

DEFINE_ADJUST(my_adjust_interface_crystal,d)
{
face_t f;
Node *v;
Node *v_shadow;

int ID = 18; /*ID of interface_crystal*/
Thread *tf = Lookup_Thread(d, ID);

int n;

real face_x, face_y, face_z; //location of face center
real node_x, node_y, node_z; //location of node

real x[ND_ND];


begin_f_loop(f,tf)
{
F_CENTROID(x,f,tf);
face_x=x[0];
face_y=x[1];
face_z=x[2];

f_node_loop(f,tf,n)
{

v=F_NODE(f,tf,n);
node_x=NODE_X(v);
node_y=NODE_Y(v);
node_z=NODE_Z(v);

//N_UDMI(v,0) = -0.1*node_y*node_z; //displacement calculated by node location
N_UDMI(v,0) = -0.1*face_y*face_z; //displacement calculated by face-center location

//Message("\nmyid=%d",myid);
}
}
end_f_loop(f,tf)
}

DEFINE_GRID_MOTION(grid_motion_crystal,d,dt,time,d time)
{
Thread *tf = DT_THREAD(dt);
face_t f;
Node *v;
Node *v_shadow;

int n;

real node_x, node_y, node_z; //location of node

SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));
begin_f_loop(f,tf)
{
f_node_loop(f,tf,n)
{
v = F_NODE(f,tf,n);
node_x=NODE_X(v);
node_y=NODE_Y(v);
node_z=NODE_Z(v);

if(NODE_POS_NEED_UPDATE(v))
{
NODE_POS_UPDATED(v);

Message("\nmyid=%d, node_x=%g, node_y=%g, node_z=%g, N_UDMI=%g",myid,node_x,node_y,node_z,N_UDMI(v,0));
//output the node location and the related displacement
NODE_X(v) = NODE_X(v) + N_UDMI(v,0); // adjust node by UDM

}

}
}
end_f_loop(f,tf)
}

DEFINE_GRID_MOTION(grid_motion_melt,d,dt,time,dtim e)
{
Thread *tf = DT_THREAD(dt);
face_t f;
Node *v;
Node *v_shadow;

int n;

SET_DEFORMING_THREAD_FLAG(THREAD_T0(tf));
begin_f_loop(f,tf)
{
f_node_loop(f,tf,n)
{
v = F_NODE(f,tf,n);
v_shadow = F_NODE_SHADOW(f,tf,n);
if(NODE_POS_NEED_UPDATE(v))
{
NODE_POS_UPDATED(v);
NODE_X(v) = NODE_X(v) + N_UDMI(v_shadow,0); // adjust node by UDM of shadow node
}
}
}
end_f_loop(f,tf)
}

[Kevin_Liu]

The answer is found in http://www.eureka.im/280.html
Related code is bolded. I have test that it can be use in DEFINE_ADJUST and DEFINE_EXECUTE_AT_END. If you want to have node value of User Defined Face Memory. You need to translate it into User Defined Cell Memory. (can be found in UDF manual), or you will get zero value. Because face memory is not available for postprocessing.

It is sometimes necessary to retrieve the values of specific variables at the nodes of your mesh. This could be done by looping over cells/faces and accessing the interpolated data at the nodes.
The UDF (DEFINE_ON_DEMAND) included in this solution provides an example for accessing pressure data on the nodes of a boundary surface.

Before executing the UDF, please make sure:
1. Data is available (case is initialized/ solved/ data file is read)
2. The correct boundary zone ID is provided
3. The correct field variable name is provided

/************************************************** ***************************
* UDF to access field variable data at nodes for a face zone
************************************************** **************************/

#include "udf.h"
#include "dx.h"
#include "mem.h"

#define ID 3 /* Zone ID (in boundary condition panel) on which node data is to be obtained */

char *what = "pressure"; /* field variable name for which data is to be extracted */

/* For single phase cases, the names of the field variables can be obtained from FLUENT TUI mode.
Example: /display/contours/ => this lists all the field variables that are available. */

/* For multi phase cases, the names of the field variables can be obtained from FLUENT TUI mode.
Example: /display/contours/phase-x => this lists all the field variables (y) that are available.
The filed variable name = "phase-x-y" => x = phase number ( 1, 2 etc.), y = variable name displayed in TUI. */

DEFINE_ON_DEMAND(my_node_values) {

real x, y;
int n;
face_t f;
Node *v;

Domain *d = Get_Domain(1);
Thread *t = Lookup_Thread(d, ID);
FILE *fp = fopen("test_file.txt", "w");

Node_Function_Values(d, what);

/* Initalize all node marks on the thread == 0 */
begin_f_loop(f, t) {
f_node_loop(f, t, n) {
v=F_NODE(f,t,n);
NODE_MARK(v) = 0;
}
}
end_f_loop(f, t);

/* Loop over the nodes and get the data */
begin_f_loop(f, t) {
f_node_loop(f, t, n) {
v = F_NODE(f,t,n);

x = NODE_X(v);
y = NODE_Y(v);

if(NODE_MARK(v) == 0) /* if not already visited */
fprintf(fp, "%gt%gt%14.8En", x , y, NODE_VALUE(v));
NODE_MARK(v) = 1;
}
}
end_f_loop(f, t);
fclose(fp);
}