Easy question (I hope)

Oskirrii · July 28, 2010, 23:17

Just need confirmation on "where" FLUENT is taking trajectory measurements when it exports X-Y data. It seems to start from 0 meters, but the particles used are 200 microns, so wouldn't FLUENT be referencing each particle at its center (for spheres)? The documentation seems to gloss over this particular detail. Thanks in advance!

-Osk

Oskirrii · July 29, 2010, 15:33

/bump someone has to know, right?

spring · August 2, 2010, 07:36

Hi Oskirrii,

you're right. When you are simulating particles as spheres ,Fluent is only referencing to the center points of this spheres, no matter how large their diameter is. This doesn't mean that the diameter does not count at all, but for example the x,y,z position of a sphere particle is taken by it's center point.
I hope this was the right answer to your question.

regards,
spring

Oskirrii · August 2, 2010, 23:41

Ok Thanks! I'm simulating multiphase particle-air lagrangian trajectories in turbulent flow, and I think I can just raise the release surface for the particles to the half-diameter height for each case to get output lagrangian trajectories. I was getting some interesting numerical effects, but this seems to help quite a bit...thanks for the help.

Oskirrii · August 2, 2010, 23:42

spring, you wouldn't happen to have a reference for where you gleaned this knowledge would you?

If not I'll keep looking this week

spring · August 3, 2010, 05:20

sorry Oskirrii,

I'vo got this kowledge by experience, because I am simlulating sphere particles (discrete phase),too. In my simulation I wanted the particles to be trapped at the walls of my mesh by contact. I noticed that the particles - no matter how different their diameters were - only stick to the wall, when their centre points "touched" the walls. When you want to make a particle injection by a "file" you must place the start positions of the particles (their centre points) a little bit INSIDE OF the mesh, so that flunt will be able to notice them. Otherwise, I think it won't work...

regards,
spring

July 28, 2010, 23:17	Easy question (I hope)	#1
Oskirrii New Member Oscar Join Date: May 2010 Posts: 14 Rep Power: 15	Just need confirmation on "where" FLUENT is taking trajectory measurements when it exports X-Y data. It seems to start from 0 meters, but the particles used are 200 microns, so wouldn't FLUENT be referencing each particle at its center (for spheres)? The documentation seems to gloss over this particular detail. Thanks in advance! -Osk

August 2, 2010, 07:36		#3
spring Member Sarah Join Date: Apr 2010 Location: Munich Posts: 30 Rep Power: 16	Hi Oskirrii, you're right. When you are simulating particles as spheres ,Fluent is only referencing to the center points of this spheres, no matter how large their diameter is. This doesn't mean that the diameter does not count at all, but for example the x,y,z position of a sphere particle is taken by it's center point. I hope this was the right answer to your question. regards, spring Last edited by spring; August 3, 2010 at 05:21.

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July 29, 2010, 15:33		#2
Oskirrii New Member Oscar Join Date: May 2010 Posts: 14 Rep Power: 15	/bump someone has to know, right?

August 2, 2010, 23:41		#4
Oskirrii New Member Oscar Join Date: May 2010 Posts: 14 Rep Power: 15	Ok Thanks! I'm simulating multiphase particle-air lagrangian trajectories in turbulent flow, and I think I can just raise the release surface for the particles to the half-diameter height for each case to get output lagrangian trajectories. I was getting some interesting numerical effects, but this seems to help quite a bit...thanks for the help.

August 2, 2010, 23:42		#5
Oskirrii New Member Oscar Join Date: May 2010 Posts: 14 Rep Power: 15	spring, you wouldn't happen to have a reference for where you gleaned this knowledge would you? If not I'll keep looking this week

August 3, 2010, 05:20		#6
spring Member Sarah Join Date: Apr 2010 Location: Munich Posts: 30 Rep Power: 16	sorry Oskirrii, I'vo got this kowledge by experience, because I am simlulating sphere particles (discrete phase),too. In my simulation I wanted the particles to be trapped at the walls of my mesh by contact. I noticed that the particles - no matter how different their diameters were - only stick to the wall, when their centre points "touched" the walls. When you want to make a particle injection by a "file" you must place the start positions of the particles (their centre points) a little bit INSIDE OF the mesh, so that flunt will be able to notice them. Otherwise, I think it won't work... regards, spring