Constant Particle Tracking

General discussion
1

As per the User Guide page 15-16, regarding Particle trajectories, "Note that at each second the last 2048 lines in cache are displayed, so their position might appear randomly. You can change the displayed number in the More... dialog".

I wondered if it is possible to track one or more particles constantly throughout their trajectory, from desorption to absorption?

Thank you,
Rebecca

2

Although this wasn't intended, you can do a trick to achieve this, if the total number of lines is smaller than 2048.

  1. In the view settings, set number of lines and dots to 2048
  2. In the global settings, set number of processes to 1
  3. In the same window, you have a "max desorption" button, which allows to stop simulation after 1 (or a small number) of particles have been fully traced. This is what you need, so only one (or a small number) of trajectories will be displayed.
3

Hi Marton,

Thank you for your advice above.

I have another question on a slight unrelated note:
I am trying to understand facet normals. So far my investigations suggest that facets are all one sided: i.e: particles will reflect off the side the normal is pointing, but pass through the other.
Firstly, is this interpretation correct?
Secondly, if this is the case, how does this affect internal geometries:
For example, if I have a thin cylinder within another cylinder and I want to measure pressure in the inner cylinder. If the normal is facing outwards, can I only measure external pressure? Do the particles from the inside then pass through this facet?

Regards,
Rebecca

4

Hello Rebecca:

  It seems that Marton didn't reply to you... he must be busy... so I do it for him.

"Firstly, is this interpretation correct?"

  Yes, correct.

"For example, if I have a thin cylinder within another cylinder and I want to measure pressure in the inner cylinder. If the normal is facing outwards, can I only measure external pressure? Do the particles from the inside then pass through this facet?"

  If you want to do that you must create a cylinder with a slightly smaller diameter (you can use the "Scale" command in the "Facet" menu for instance... a very small reduction like 0.999 works fine, and re-orient the normals of the newly created facets (use "Copy facet" in "Scale"!!).

  Hope it helps,

   Roberto

 

5

Hi Roberto,

Thank you for your helpful response. I have tried this method, and unfortunately although I have ensured that all of the normals are facing in the correct way (i.e. external facing outwards, internal pointing inwards), the molecules appear to get trapped within these small gaps between facets. Can you think of any way to prevent this?

Rebecca

6

Hello:

 

  I am not sure I understand what's going on, without seeing the file/geometry.

  Could you please e-mail it to me? Thanks.

  roberto.kersevan@cern.ch