How can I twist a surface with UDF? -solved-
 

Hi all,
I have to twist a surface through mesh-motion. How can I do that? How should I write the UDF? Please help me...
Thanks in advace!

I solved the problem, with define_grid_motion.
If somebody is interested, here is the UDF.




#include"udf.h"
DEFINE_GRID_MOTION(twist,domain,dt,time,dtime)
{
Thread *tf = DT_THREAD(dt);
face_t f;
Node *v;

real NV_VEC(axis);
real delta,xaxis,yaxis,teta,xn,yn,dx,dy,H;
int n;


H = 0.1; /*z-dimension of the model*/
teta = 10*3.14/180; /*rotation angle*/


begin_f_loop(f,tf)
{
f_node_loop(f,tf,n)
{
v = F_NODE(f,tf,n);
/* update node if the current node has not been previously
visited when looping through previous faces */
if ( NODE_POS_NEED_UPDATE (v))
{
/* indicate that node position has been update
so that it's not updated more than once */
NODE_POS_UPDATED(v);
xn = cos(teta)*NODE_X(v)-sin(teta)*NODE_Y(v);
yn = sin(teta)*NODE_X(v)+cos(teta)*NODE_Y(v);
dx = xn-NODE_X(v);
dy = yn-NODE_Y(v);
xaxis = dx/sqrt(pow(dx,2) + pow(dy,2));
yaxis = dy/sqrt(pow(dx,2) + pow(dy,2));
NV_D(axis, =, xaxis,yaxis, 0.0);
delta = sqrt(pow(dx,2) + pow(dy,2))*NODE_Z(v)/H;
NV_V_VS(NODE_COORD(v), =, NODE_COORD(v), +, axis,*,delta);


}
}
}
end_f_loop(f,tf);
}

Hey guys.. I need to move a 2D airfoil through certain angle of attack.. now if I dont want to use CG_Motion.. do you think I can do it through GRID_MOTION.. Like may be threading all the nodes across surface and moving them all..