Learning Forum

[CatherineIl]

Hello,

I would like to simulate an undulating airfoil using udf. Unfortunately, I do not have a lot of udf experience and I do not know how to do it. I know that I can use define_grid_motion but I am not sure how. Could anyone please help me? I would really appreciate that as I needed it for my uni project. 

Thank you in advance, 

Catherine 

[Karthik Remella]

Hello Catherine,

I always find the Fluent Customization Manual to be the best place for starting a UDF. Since there are multiple examples of tested UDFs illustrated in this manual, I generally tend to use them directly (at first) and then modify it to suit my modeling needs. Here is a link to the DEFINE_GRID_MOTION macro which will point you to an example. Please let me know here if you are able to access this link. I've also posted a screenshot of the UDF here for your help.

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v193/flu_udf/flu_udf_sec_define_grid_motion.html?q=define_grid_motion

Best,

Karthik

[Keyur Kanade]

also please go through some introduction to udf. 

https://www.youtube.com/watch?v=PXTPfREgLzE

 

[CatherineIl]

Hello again, 

Thank you very much for your reply. 

Unfortunately, I have tested this and my airfoil does not change at all even if I change the parameters and I do not understand why as I used the same as the manual.

[CatherineIl]

The only one that I could find is the one below which deforms and increases the length but I do not how to deform it only. 
#include"udf.h"
#include"unsteady.h"
#include"dynamesh_tools.h"
#include "udf.h" 
DEFINE_GRID_MOTION(beam,domain,dt,time,dtime) 
{ 
Thread *tf; 
face_t f; 
int n; 
Node *v; 
/* get the thread pointer for which this motion is defined */ 
tf=DT_THREAD(dt); 
begin_f_loop(f,tf) 
{ 
f_node_loop(f,tf,n) 
{ 
v = F_NODE(f,tf,n); 
NODE_Y(v)=NODE_Y(v)+fabs(NODE_X(v))*dtime; 
} 
} 
end_f_loop(f,tf); 
} 

[Keyur Kanade]

can you please insert some images of your geometry, mesh and explain what exactly you are trying to do. 

[CatherineIl]

Finally, I found my error so I managed to make it work. Thank you very much for your time. 

[Naren B]

Hello Catherine, 

I have been working on structure deformation in Ansys using DEFINE_GRID_MOTION UDF code.. But, the available published code showing more errors. I dont know what wrong with the code...would you be kind enough to share your code, so that I can learn and develop my own code..Im eagerly waiting for positive response from you..Your help is highly helpful for me..

Thanks in advance..