[mecamor]

Originally Posted by Amir

The easiest way for you is writing a UDF for the piston and hook to to the piston and with appropriate setting in dynamic mesh panel (smoothing & re-meshing) change the fluid zone cells. it's also better to take a look over manual.

Amir

Hi Amir
I wrote the UDF of the piston, but when compiling with C 13 or it Fluent There's an error in line 3. How I should do. thank you
Error: C:\Program Files\ANSYS Inc\v130\fluent\ntbin\win64\PISTON2.c: line 3: parse error.

How I should do. thank you
#include "udf.h"
#include "dynamesh_tools.h"
static real v_prev= 0.0;
DEFINE_CG_MOTION(piston, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
real NV_VEC (A);
real force, dv;
/* reset velocities */
NV_S (vel, =, 0.0);
NV_S (omega, =, 0.0);
if (!Data_Valid_P ())
return;
/* get the thread pointer for which this motion is defined */
t = DT_THREAD ((Dynamic_Thread *)dt);
/* compute pressure force on body by looping through all faces */
force = 0.0;
begin_f_loop (f, t)
{
F_AREA (A, f, t);
force += F_P (f, t) * NV_MAG (A);
}
end_f_loop (f, t)
/* compute change in velocity, i.e., dv= F * dt/ mass;
velocity update using explicit eulerformula */
dv= dtime* force / 50.0;
v_prev+= dv;
CX_Message ("time = %f, x_vel= %f, force = %f\n", time, v_prev, force);
/* set x-component of velocity */
vel[0] = v_prev;
}

[Amir]

refer to:
http://www.cfd-online.com/Forums/flu...-rotation.html