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 teymourj February 9, 2010 02:06

UDF for defining a body force in Singel ROtating Reference Frame

Dear all,

I am trying to use Discrete Phase Model (DPM) to look at particle behavior in the solution of my Single Rotating Reference Frame (SRF) which contains my countinues fluid.

As long as SRF has rotating frames, therefore a Centrifugal and Coriolis term will be added to the equation of force balance of the particles. What I need to do, is writing a UDF which calculates these two forces. Then compile it with my model, so that it cancels those two additional forces.

I wrote a UDF based on UDF manual section 2.5.2 file:///usr/ansys_inc/v120/fluent//f...udf/node67.htm as follow, but it did not work out and I get error when I want to compile it. I was wondering if anyone can help me with that.

/* UDF for computing the force due rotating refrence frame on a particle */

#include "udf.h"
#define ROHR 1.5

/* density ratio of particles (roh/roh_p) */
#define OMEGA 1.78

/* Calculate some of centrifugal & coriolis force on a particle */
/* axis of rotation is "Y" and there are two force components in "X" and "Z" */ /* Fx= (1-ROHR)*OMEGA^2*x + 2*OMEGA*(u_z,p - ROHR*u_z), Fz= (1-ROHR)*OMEGA^2*z + 2*OMEGA*(u_x,p - ROHR*u_x) */

DEFINE_DPM_BODY_FORCE(particle_body_force,p,i)

{
real bforce=0;
if(P_TIME(p)>=TSTART)
{ if(i==0)

bforce=(1-ROHR)*OMEGA^2*P_INIT_POS(p)[0] + 2*OMEGA*(P_VEL(p)[2] - ROHR*rel_vel[2]);

else if(i==2) bforce=(1-ROHR)*OMEGA^2*P_INIT_POS(p)[2] + 2*OMEGA*(P_VEL(p)[0] - ROHR*rel_vel[0]); }

else bforce=0.0;

/* an acceleration should be returned */
return (bforce/P_MASS(p));

-teymourj

 teymourj July 28, 2011 13:46

Solution!

I found the solution to this problem. Read the MRF/SRF limitations for tracking particles in ANSYS FLUENT user's guide at:

// User's Guide :: 1 // 10. Modeling Flows with Moving Reference Frames // 10.3. Flow in Multiple Moving Reference Frames // 10.3.1. The Multiple Reference Frame Model

Note that the particle track in rotating reference frame for inert particles is MEANINGLESS (see the user's guide). You should use the TUI command to track particles and extract their data in absolute reference frame.

Best,

Teymour

 mingersai July 28, 2011 17:45

THANK YOU SO MUCH!!!!!!
That's why I can not get anyting. With rotating reference frame.
Ansys customer support seems to made a mistake, I had asked them whether I can inject particles without being affected by rotation reference frame and they said no......

I had been stucked here for a long time.

Quote:
 Originally Posted by teymourj (Post 317926) I found the solution to this problem. Read the MRF/SRF limitations for tracking particles in ANSYS FLUENT user's guide at: // User's Guide :: 1 // 10. Modeling Flows with Moving Reference Frames // 10.3. Flow in Multiple Moving Reference Frames // 10.3.1. The Multiple Reference Frame Model Note that the particle track in rotating reference frame for inert particles is MEANINGLESS (see the user's guide). You should use the TUI command to track particles and extract their data in absolute reference frame. Best, Teymour

 mahayheidari August 18, 2016 14:33

can you explain it for me ?
i have problem in it yet

 teymourj August 18, 2016 15:01

@mahayheidari: Please be specific about your problem and what you are not understanding and I will provide you inputs.

This thread is very old and I am not sure what you need me to explain. Explain your problem from scratch.

 mahayheidari August 18, 2016 15:07

I have a prticle in a fluid
And the particle have transitional and rotational movement
I simulate it
But the particle just have transitional movement
And it cant rotate
I want to know what should i do
Thanks

 teymourj August 18, 2016 15:09

What are the models you are using to simulate the flow field and particle respectively in FUENT?

 mahayheidari August 18, 2016 15:13

There is a canal that a circular particle move in it
If you want i will sent the picture

 mahayheidari August 18, 2016 15:15

Dynamic mesh
Remeshing
Smoothing
6dof

 teymourj August 18, 2016 15:33