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-   -   Path status in DPM BC UDF (http://www.cfd-online.com/Forums/fluent/39725-path-status-dpm-bc-udf.html)

HS February 20, 2006 09:28

Path status in DPM BC UDF
 
Hi again!

I am writing a DPM boundary condition as a UDF.

After executing some lines of code, I would like to use the standard "escape" boundary condition. Is all I have to do to return the correct path status then? And which one should it be? return PATH_STOP; ?

Thanks, Henrik

HS February 20, 2006 09:31

Re: Path status in DPM BC UDF
 
Maybe I should mention, the ones available are:

PATH_END

PATH_ACTIVE

PATH_BREAK

PATH_ABORT

PATH_STOP

/Henrik

SJSW June 12, 2014 04:14

Thank you, HS. It's helpful to know these functions.
The "escapse" condition seems to be attained at "wall" boundary condition when using "PATH_END," but I don't know if it works at the "pressure-outlet" boundary condition. Ther eare some explainations about the DPM boundary condition such as "reflect," "trap," ",escape" "wall-jet,""wall-film," and "user-defined," shown in the tag "DPM" of the boundary condition "Wall" (ANSYS14.0).

and could you tell me where and how to find look up functions like PATH_END or PATH_STOP, for I never see it in a manual and don't know its meaning. :(

pakk June 12, 2014 04:41

Fluent UDF manual 2.5.1:

"For the return status PATH_ACTIVE, the particle continues to track. For the return status PATH_ABORT, the particle will be stopped and considered to be aborted. For the return status PATH_END, the particle will be stopped as well, but considered to have escaped from the domain."

If you want a particle to be "trapped", use PATH_ABORT; if you want a particle to be "escaped", use PATH_END.
Honestly, I don't know if there is any aspect in which Fluent treats "trapped" particles differently from "escaped" particles, but if I used this I try to choose the most logical condition in my situation.

As of Fluent 15.0, there are seven different statuses (see dpm_types.h, somewhere in your Fluent folder):

PATH_END
PATH_ACTIVE
PATH_BREAK
PATH_ABORT
PATH_STOP
PATH_NON_LOCAL_PERIODIC
PATH_NON_LOCAL

They are listed without explanation, and I don't know more. I would guess that PATH_BREAK indicated a break-up of a particle, and that PATH_NON_LOCAL_PERIODIC and PATH_NON_LOCAL might have to do with parallel issues. I don't know when PATH_STOP should be used, nor what it does.

SJSW June 12, 2014 07:12

Topic "Discrete Phase Boundary Condition Types" in ANSYS14.0 manual has some explanations about these boundary condition types: "reflect," "trap," ",escape" "wall-jet,""wall-film," and "user-defined."


> For the return status PATH_ACTIVE, the particle continues to track.
When "Wall" boundary condition and UDF file with "PATH_XXXX" replacing "PATH_ABORT" the code described in 2.5.1. DEFINE_DPM_BC 2.5.1.3. Example 1, whch is an example of inert particle rebound at wall, some functions such as "ABORT," "BREAK" and "STOP" can't be distinguished.

Somehow, "ACTIVE" seems have some particle dispeared??:confused:

ABORT
http://picmoe.net/src/1402571753665s.jpg

ACTIVE
http://picmoe.net/src/1402571731225s.jpg

BREAK
http://picmoe.net/src/1402571707257s.jpg

END
http://picmoe.net/src/1402571678106s.jpg

STOP
http://picmoe.net/src/1402571447752s.jpg


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