[Sigurd]

Hi!

I am trying to compile a udf for a rotating shaking flask, or an Orbitally Shaken Bioreactor for those of you familiar with those.

The code I am using is pretty basic I think, but it returns an error of:

udf_names.c(7) : error C2059: syntax error : '}'
udf_names.c(8) : warning C4034: sizeof returns 0

and this is the code I am using:

#include "udf.h"
#define pi 3.141592654
#define d_o 0.025 //shaking diamter [m]
 DEFINE_ZONE_MOTION(rotation,omega,axis,origin,velocity,time,dtime)
{
 real omega_o, theta, r_o;

 omega_o=pi*2; //angular velocity of shaker table [rad/s]
 *omega=-omega_o; //angular velocity of shake flask [rad/s]
 theta=omega_o*(time+dtime); //angular position of shake flask [radians]
 r_o=d_o/2; //shaking radius [m]
 
 origin[0]=r_o*cos(pi+theta);
 origin[1]=r_o*sin(pi+theta);
 origin[2]=0;
}

Any help would be greatly appreciated!

Thanks
Sigurd

[MandatoryMadness]

Hi!


Sorry to revive this thread


I am currently working on a similar problem in Fluent. Have you found a solution for the shake flasks? My UDF code looks similar and can be compiled etc. but the movement of the mesh is not right.



This is the code:

#include "udf.h"
#define PI 3.14592654
DEFINE_ZONE_MOTION(rotation, omega, axis, origin, velocity, time, dtime)
{
real theta0, theta1, omegac, omegar, rdar, ox, oy;
omegar = -20.94;
omegac = -omegar;
rdar = 0.0125;
theta0 = PI;
theta1 = omegar*(time+dtime);
*omega = omegac;
origin [0] = rdar*cos(theta0+theta1);
origin [1] = rdar*sin(theta0+theta1);
origin[2] = (0,0);
}

[obscureed]

Hi Vincent,

Does that code really compile? "origin[2] = (0,0);" doesn't look like correct C to me.

Moving the origin is a rather mind-bending thing to do here. If you just want oscillatory rotation, the origin stays constant. If you want oscillatory rotation plus some other motion, you probably need to add some translation velocity. For the motion of a beaker on a tray, it could all be translation velocity.

Good luck!
Ed

[MandatoryMadness]

Hi Ed,



Thanks for the input! The code compiles fine, I will try another format just to make sure this is not the cause of the incorrect movement.



Unfortunately, this setup requires two motions. 1) The vessel rotating around the origin and 2) the vessel rotating around itself in the opposite direction - so effectively the vessel always faces the same direction during the rotation.



How would you add a translation velocity?



Many thanks and regards
Vince

[obscureed]

Hi Vince,

Well, I'll put it another way: what do you intend to be the result of "origin[2] = (0,0);"? It doesn't look familiar to me.

(Rotation about one axis + equal and opposite rotation about another axis) = no rotation, only translation. Look at the velocity argument in DEFINE_ZONE_MOTION.

A couple of very minor comments while I'm here: You will find that M_PI is already defined for pi. You can try to finesse the time for evaluating functions -- time, or time+dtime, or something in between -- but in general it's easier to stick with time.

Good luck!
Ed

[S_Tanuj]

I am trying to give the zone motion using UDF. Below is the code attached. Though it shows no error on compilation, zone does not seem to rotate as per code. Geometry is simple 2-D closed-loop pipe and origin is at the bottom. Is there anything wrong in UDF?

#include "udf.h"
#define Freq 0.1
#define angular_freq 2.0*M_PI*Freq
#define tetmax 15.0*M_PI/180

DEFINE_ZONE_MOTION(shm, omega, axis, origin, velocity, time, dtime)
{
*omega = tetmax*angular_freq*cos(angular_freq*time);

velocity[0] = 0.0;
velocity[1] = 0.0;
velocity[2] = 0.0;

omega[0] = 0.0;
omega[1] = 0.0;
omega[2] = *omega;

}

[AlexanderZ]

remove * before omega
was:

 *omega

to be:

 omega

[S_Tanuj]

Earlier I did the same but there was error because of not including "*", and the error was-

zone_motion.c
..\..\src\zone_motion.c(8) : error C2440: '=' : cannot convert from 'double' to 'real *'
..\..\src\zone_motion.c(16) : error C2440: '=' : cannot convert from 'real *' to 'real'

After including "*", it easily compiled.

[AlexanderZ]

#include "udf.h"
#define Freq 0.1
#define angular_freq 2.0*M_PI*Freq
#define tetmax 15.0*M_PI/180

DEFINE_ZONE_MOTION(shm, omega, axis, origin, velocity, time, dtime)
{
velocity[0] = 0.0;
velocity[1] = 0.0;
velocity[2] = 0.0;

omega[0] = 0.0;
omega[1] = 0.0;
omega[2] = tetmax*angular_freq*cos(angular_freq*time);
}

[S_Tanuj]

Originally Posted by AlexanderZ

#include "udf.h"
#define Freq 0.1
#define angular_freq 2.0*M_PI*Freq
#define tetmax 15.0*M_PI/180

DEFINE_ZONE_MOTION(shm, omega, axis, origin, velocity, time, dtime)
{
velocity[0] = 0.0;
velocity[1] = 0.0;
velocity[2] = 0.0;

omega[0] = 0.0;
omega[1] = 0.0;
omega[2] = tetmax*angular_freq*cos(angular_freq*time);
}

The code shoes no error BUT using frame motion in "cell zone boundary condition" motions is NOT OBSERVED. What could be the reason for this. Though mass flow rate fluctuate which point out towards effect of UDF.