[278379rea]

hi every one!

I am trying to use udf in fluent to simulate NACA0012 airfoil with this dynamic equation:


I am just a beginner of the udf, and I think I can simulate this case by DEFINE_CG_MOTION. But how to change the rotation aixs or define it? The omega[] means rotation by x/y/z axis, right? I think I need to give the axis a Uy to describe the motion. So who can tell me how to define my axis rather than xyz axis?

[guoqingzhang]

Originally Posted by 278379rea

hi every one!

I am trying to use udf in fluent to simulate NACA0012 airfoil with this dynamic equation:


I am just a beginner of the udf, and I think I can simulate this case by DEFINE_CG_MOTION. But how to change the rotation aixs or define it? The omega[] means rotation by x/y/z axis, right? I think I need to give the axis a Uy to describe the motion. So who can tell me how to define my axis rather than xyz axis?

Hi, Hong, I had the same problem that sepecify the rotational axis of arm which is parallel with the Z-axis in DEFINE_CG_MOTION. I found a may-helpful solution as shown below, but unfortunetly it didn't work as i expected. Did you solve the problem? If yes, could you send me a e-mail? guoqingzhang_1989@126.com. Thanks a lot.

# include "udf.h"
# define a0 15791.0742
DEFINE_CG_MOTION(arm_motion,dt,cg_vel,cg_omega,tim e,dtime)
{
real NV_VEC(axis), NV_VEC(origin);

NV_D(origin, =, -37.32952, 5.627642, 0.0);
NV_D(axis, =, 0.0, 0.0, 1.0);

if(time>=0&&time<0.003)
{
cg_omega[2]= -a0*time;
}
else if(time>=0.003&&time<0.007)
{
cg_omega[2]= -a0*0.003;
}
else if(time>=0.007&&time<0.010)
{
cg_omega[2]= -(a0*0.010-a0*time);
}
else if(time>=0.020&&time<0.023)
{
cg_omega[2]= a0*(time-0.02);
}
else if(time>=0.023&&time<0.027)
{
cg_omega[2]= a0*0.003;
}
else if(time>=0.027&&time<0.030)
{
cg_omega[2]= a0*0.010-a0*(time-0.02);
}
}