[roopesh99]

Dear Friend,
Thanks a lot for your's strong help and guidance. Presently, i made changes according to your suggestion. It is working good for rectangle geometry. When, i am using inlet and out is equal to 2 cm [i also used mesh size 2cm and particle size dia 1.5cm], then particles are not recycling.
See that attached figures for detail. Can say, in figure 1 small inlet as well as small outlet and in fig no. 2 used wider inlet and small outlet, but both cases are not working.
Note:Particle reaching to the top boundary and recycle txt file generated but particles not recycling.
Note: Pls try your case also for small inlet and outlet and can see yourself.
Pls suggest the solution for operating this type cases.
My second question, can we give recycle particle inlet in 3d at some fixed inlet point?
// send particle to the inlet boundary
P_POS(p)[2] = 0.;
P_POS(p)[0] = 0.15;
P_POS(p)[1] = 0.075;
or in 2d
P_POS(p)[2] = 0.;
P_POS(p)[0] = 0.15;
Thank you!!

[roopesh99]

Dear friend, i have one question, how can we write information in txt file about particles again enter with which velocity, after recycled by UDF?

[roopesh99]

Dear friend,
i want to see inlet and oulet velocity of recycle. Can i use P_POS0(p)[0 or 2 or 3] and P_POS(p)[0 or 2 or 3] together in fprintf. My second question is for recycling the particles, particle velocity not matter, only touch to thread,face etc. works.

[`e`]

Originally Posted by roopesh99

Presently, i made changes according to your suggestion. It is working good for rectangle geometry. When, i am using inlet and out is equal to 2 cm [i also used mesh size 2cm and particle size dia 1.5cm], then particles are not recycling.

How are they not recycling, where are the particles terminating and what is your UDF and geometry coordinates (specifically, the inlet and outlet)?

Originally Posted by roopesh99

Note:Particle reaching to the top boundary and recycle txt file generated but particles not recycling.

Are the particles stuck or escaped?

Originally Posted by roopesh99

My second question, can we give recycle particle inlet in 3d at some fixed inlet point?
// send particle to the inlet boundary
P_POS(p)[2] = 0.;
P_POS(p)[0] = 0.15;
P_POS(p)[1] = 0.075;
or in 2d
P_POS(p)[2] = 0.;
P_POS(p)[0] = 0.15;

Yes, this code should scale fine with three dimensions. In 2-D, you'll need to use P_POS(p)[0] (x-coordinate) and P_POS(p)[1] (y-coordinate). For 3-D, you'll also include the P_POS(p)[2] macro for the z-coordinate. You've mentioned the z-coordinate for the 2-D case.

Originally Posted by roopesh99

how can we write information in txt file about particles again enter with which velocity, after recycled by UDF?

You can add additional variables to the data file, including velocity by modifying the fprintf line (added after the positions):

fprintf(fp,"%e %e %e %e %e %e %d %e\n",P_POS(p)[0],P_POS(p)[1],P_POS(p)[2],P_VEL(p)[0],P_VEL(p)[1],P_VEL(p)[2],p->part_id,P_TIME(p));

Originally Posted by roopesh99

want to see inlet and oulet velocity of recycle. Can i use P_POS0(p)[0 or 2 or 3] and P_POS(p)[0 or 2 or 3] together in fprintf. My second question is for recycling the particles, particle velocity not matter, only touch to thread,face etc. works.

The velocity before and after the recycle is unchanged and this value is copied to the data file with the procedure above. You could include the P_POS0 macro as well; the indices should be 0, 1 and 2 (not 3).

[roopesh99]

Dear Friend, thanks a lot for nice reply, my first question is why you used the P_USER_REAL(p,0) and P_USER_REAL(p,1) both . Second, you are only updating only to P_USER_REAL(p,0) = P_USER_REAL(p,0) + 1 not to P_USER_REAL(p,1)

[`e`]

Originally Posted by roopesh99

my first question is why you used the P_USER_REAL(p,0) and P_USER_REAL(p,1) both

The first memory, P_USER_REAL(p,0), is used for storing the number of times this parcel has been recycled. The second memory, P_USER_REAL(p,1), is used as a flag which is true when the particle has reached the outlet area (it's a fix as Fluent was calling this macro multiple times before updating the particle position to the inlet).

Originally Posted by roopesh99

Second, you are only updating only to P_USER_REAL(p,0) = P_USER_REAL(p,0) + 1 not to P_USER_REAL(p,1)

Yes, that's intentional (see above).

[roopesh99]

Thanks for such guidance... bye

[RB_90]

Dear forum members,

I would like to use the suggested approach to relocate particles to the inlet when they would normally leave the domain. However when I look at the particle tracks they are not moving back but simply stay at the outlet.

My code:



#include "udf.h"

DEFINE_DPM_BC(continue_tracking,p,t,f,f_normal,dim )
{
return PATH_ACTIVE;
}

DEFINE_DPM_SCALAR_UPDATE(recycle_particles,c,t,ini tialize,p)
{


if (P_POS(p)[2]>0.09)
{
P_POS(p)[2] = 0.0;
}
}


I also tried to use an execute at end approach, which reulted in my particles being actually moved to the inlet but jumping back to the outlet for the next iteration. My guess would therefore be that fluent somehow overwrites my values for the position with the previous values or calculates a the new position based on the old values. I also set the unsteady tracking.

I would be really glad if someone has a suggestion how to resolve this

[walid abou hweij]

Dear Friends,

The posts are important, but I hope u could help me in this problem.

Running a steady flow I have a pipe of 40 mm diameters and I need to find the residence time distribution for a pipe that is 4 times the original one. Accordingly, the DPM with massless particles under steady state were used. I need the particles that exit to be recycled 4 times. As it appears in the UDF that you have provided, that the transient condition determines the number of times the particles crosses the outlet; however, in my case I need the opposite way round, that is given number of crosses that the particles passes the outlet, I need the particles properties (position, velocity and time) when they cross the outlet. Please provide me with an idea as soon as possible.

Thanks in advance.
Walid

[walid abou hweij]

Dear Friends,

The posts are important, but I hope u could help me in this problem.

Running a steady flow I have a pipe of 40 mm diameters and I need to find the residence time distribution for a pipe that is 4 times the original one. Accordingly, the DPM with massless particles under steady state were used. I need the particles that exit to be recycled 4 times. As it appears in the UDF that you have provided, that the transient condition determines the number of times the particles crosses the outlet; however, in my case I need the opposite way round, that is given number of crosses that the particles passes the outlet, I need the particles properties (position, velocity and time) when they cross the outlet. Please provide me with an idea as soon as possible.

Thanks in advance.
Walid

[eddy123]

Hi guys,
I am working on 2D Riser simulations using DDPM approach. I have a simple rectangular domain having boundaries inlet (velocity inlet), outlet (pressure outlet) and wall as is shown in attached Figure. I want to recycle the particles which after leaving from outlet domain recirculate back to the inlet. I am not good at all in UDF skills. I saw your posts which are useful regarding my issue. So i want to know that how can I change the UDF as shown below this message according to my 2D problem. If you guys can help me it will be encouraging for me. Thanks.



#include "udf.h"

DEFINE_DPM_BC(continue_tracking,p,t,f,f_normal,dim )
{
return PATH_ACTIVE;
}

DEFINE_DPM_SCALAR_UPDATE(recycle_particles,c,t,ini tialize,p)
{
FILE *fp;

if (P_POS(p)[0]<0.08333)
{
P_USER_REAL(p,1) = 0.;
}

if (P_POS(p)[0]>0.91667 && P_USER_REAL(p,1) == 0.)
{
// save particle position to a text file
fp=fopen("recycleparticles.txt", "a"); // x, y, z particle positions [m], particle ID [#] and time [s]
fprintf(fp,"%e %e %e %d %e\n",P_POS(p)[0],P_POS(p)[1],P_POS(p)[2],p->part_id,P_TIME(p));
fclose(fp);

// save the number of times this particle has been recycled
P_USER_REAL(p,0) = P_USER_REAL(p,0) + 1.;
P_USER_REAL(p,1) = 1.;

// send particle to the inlet boundary
P_POS(p)[0] = 0.;

P_POS(p)[1] = P_POS(p)[1] + 0.0833;

[eddy123]

Attached figure.