[a.ali]

Hi
I'm trying to simulate a off center rotating 2D disk in a channel and I have problem. one send me an UDF and I compiled it but I could not change the center of rotation. here the UDF and problem geometry.

#include "udf.h"
static real v_prev = 0.0;
DEFINE_CG_MOTION(airfoil,dt,vel,omega,time,dtime)
{
real NV_VEC(A);
real dv;
/* reset velocities */
NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);
omega[2] = 10;
}

[luna125]

Originally Posted by a.ali

Hi
I'm trying to simulate a off center rotating 2D disk in a channel and I have problem. one send me an UDF and I compiled it but I could not change the center of rotation. here the UDF and problem geometry.

#include "udf.h"
static real v_prev = 0.0;
DEFINE_CG_MOTION(airfoil,dt,vel,omega,time,dtime)
{
real NV_VEC(A);
real dv;
/* reset velocities */
NV_S(vel, =, 0.0);
NV_S(omega, =, 0.0);
omega[2] = 10;
}

hi, guys,

did you solve the issue? i have the same issue about how to define a center of rotation since the rotation is off the center of gravity in fluent UDF.

[luna125]

hi,
the fluent17.1 has dialogs to define the rotate center.

[rjm1982]

Hello, I am also struggling with something similar. I am trying to have a 2D airfoil translating and rotating at the same time. The centre of rotation needs to be the 1/3rd chord of the airfoil, so the centre of rotation is moving at every time step due to the translation. I am trying to use DEFINE_CG_MOTION, but so far without success.

Does anyone know how I can specify the moving centre of rotation please?

[rjm1982]

Update: the centre of gravity dialogue boxes correspond to the initial values. These are updated automatically by Fluent. Therefore all you need to do is input the initial location of the centre of gravity/rotation and Fluent will update it automatically as the body moves!