Dear Peng Chen,

Here is a UDF for dynamic meshing used for Dynamic Stall investigation for VAWT.

#include "udf.h"

#define angular_freq 41.89

#define alphaone 10.0*M_PI/180

DEFINE_CG_MOTION(heda, dt, cg_vel, cg_omega, time, dtime)

{

real omega;

omega = alphaone*angular_freq*cos(angular_freq*time);

cg_vel[0] = 0.0;

cg_vel[1] = 0.0;

cg_vel[2] = 0.0;

cg_omega[0] = 0.0;

cg_omega[1] = 0.0;

cg_omega[2] = omega;

}

The relevant paper link: Conference Paper Dynamic Stall Investigation of Two Dimensional Vertical Axis...

A manual of ANSYS Fluent UDF is attached from where you can get in details explanation for how to construct UDF.

Regards

I have this manual and I have learned some examples in it, but I still don't konw how to use udf to sovle my problem.

Thanks for your answer

Can I get a brief info about your research?

Thank you

Sir, I want to do some research about the moving boundary problem of human vessels,and now, I have data scanned by CT at 20 time points in one heart cycle, I can build models of different time frames. How to make the vessel move in fluent? I read some references and UDF could do it, but I dot't have clear idea, would you like give me some advice? Thank you very much.

The simple answer to your question is that you can write a UDF to describe the motion of the dynamic mesh, which means mathematical description of the motion of each node over time.

For your case, I assume vessel motion simply involving expansion and constriction, then you can use DEFINE_GRID_MOTION function to define the motion of each node. An example using DEFINE_GRID_MOTION is provided in the manual.

If you have trouble with writing the UDF, I may help you with that if you can provide more information about the vessel motion.

Sir，I know that DEFINE_GRID_MOTION is used to describe the motion of vessel wall, Now I can get the 20 stl models, and I have got mesh file for each model, and each node in each model can be described with coordinate. Now the problem is how I can put the information of displacement on each node from this time step to the next. I am gald if you could answer my problem, and I can also provide the mesh information about the vessel model. Would you like to leave your E_MAIL so that I can send files to you. And thank you again!

Hi Peng,

Thank you for sharing stl and csv files. Appologize that I just realize your case looks very complicated. Based on my understanding, you have node location at different time steps and want to update the location of each node for each time step. I do not have a simple answer to your problem. For UDF DEFINE_GRID_MOTION, you need to come up with a single equation which describes the motion of all the nodes.

For now, maybe you want to try finding a mathematical equation for nodes motion and matching that to clinical data (I guess that's where your data comes from).

Hi,Sir

the gif that you send to me have shown what I want to do, you mean I need to get one equation to describe motion of nodes.? However, the number of nodes at different time steps is also different, I can calculate displacement at all nodes of the model at the first time step, now the question is how I can define displacement on different nodes.

Thank you