Hi,

I'm tracking a particle in a driven cavity. I want to be able to track the particle every 0.1 seconds. The problem is that the report interval I have access to in the fluent 5.5 GUI is only step by step. This creates files that are way too large for me to manage.

Is there a way writing a simple UDF so that I can get the position every 0.1 seconds? The only macro that I've found that is remotely useful is DEFINE_DPM_OUTPUT, but his only gives me information when it passes through a plane.

Any ideas?

Also, what is the variable name for a particle's position? I've found the variables for particle properties (eg P_TIME(p) for particle time) but there is none for particle position. I was thinking about using an interpreted UDF, but of course there is no function hook for each DPM time step.

Cheers,

Matt.

Hi Matt

yes you are right, there is not a macro for the particle position available to the users. i sugguest that you talk to the Fluent support to get this macro, or you write a UDF, knowing the current time for a particle and the the particle velocity you can determine the x,y,z position of you particle relative to a point injection.

I have another idea, I guess you are specifing Lenght scale in the discrete phase interphase, how about if you specify the step lenght factor, so that you get uniform time step.

Also you can use file>write>start particle history

Regards

Alex Munoz

I fooled a bit with version 6 and there is a macro available for particle position called "(P_POS(p,i)" where i is 0,1,or 2 for the three co-ordinate directions.

You can do your own UDF for particle conditions at fixed times. I don't remember if there is an explicit variable "particle time" available to the user, but the differential time for each particle step is there, so you can sum it up.

Someone has posted particle UDFs on this cfd-online site which you can find and modify as needed - good luck.