[andyhor]

Hi everyone,

I am first time user to UDF, and using ansys 2016. I need UDF for the lower momentum boundary condition.

I am trying to put expressions for a 3D , 1/8 concentric sphere, and the fluid is driven by lower surface to oscillate with respect to z-axis.

I have attached the 2 diagrams below of the fluid surfaces.

In 2019 version, i can put the boundary conditions as expression as sin(t/1[s])*1[rad/s] for the lower oscillating surface.

If I want to write in UDF, can I write in this way ? Please help.

[CODE]
/************************************************** ********************
oscillatingwall.c
UDF for specifying a transient simple harmonic motion
************************************************** *********************/

#include "udf.h"
#define angular_freq 1
DEFINE_GRID_MOTION(inneroscillatingwall, dt, cg_vel, cg_omega, time, dtime)

{
Thread*t; /*is the pointer to the structure that store*/
real omega;

/* reset velocities */
NV_S (vel, =, 0.0);
NV_S (omega, =, 0.0);

t=DT_THREAD(dt); /*Get the tread pointer for which this motion is defined*/

omega = sin(angular_freq*time); /*rotional speed about axis*/

cg_vel[0] = 0.0; /*x y z translation*/
cg_vel[1] = 0.0;
cg_vel[2] = 0.0;

cg_omega[0]=0.0; /* x y z rotational axis*/
cg_omega[1]=0.0;
cg_omega[2]=omega;

}