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Hello Akash,

I’d need a model file or a screenshot uploaded here to know what “bottom” means and to imagine your geometry. Can you add it please?

Hello Marton,

Thankyou for your reply.

This is the geometry, bottom selected facet is the one i am refering to.

Thanks in advance.

Akash

It seems correct for me. Check if there are additional non-holed facets left over (if you creatted the holed ones with the Create Difference command), check facet normal directions and check leaks. If it doesn’t work upload the file here and I’ll have a look.

Hello Marton,

I have tried to simulate the problem, i am able to see the conical shape of particles exiting through the hole as expected, but they are in the form of leaks, i am not able to get them as normal paricles.

Your inputs are appreciated.

I am attaching my zip file.

Thankyou in advance

Akash

/sites/default/files/u349/Particles.zip

The file you sent me is different from the screenshot.

I don't see any holed facets, only full circles.

As suggested in my previous comment, the problem is with the normal directions (facet #2 normal pointing outwards), and the non-holed facets #39 and #40.

The reason that some particles go through in the centre is that facet 39 and 84 are both in the same plane, resulting in undefined behavior (either reflection or pass-through).

To fix your geometry, you need to swap normal on facet 2, and create the holed differences of facet 39 with 84, and facet 40 with 83, then delete the originals 39, 40, 83, 84.

Attaching fixed file.

particles_fixed.zip

Hello Marton,

I think i was not deleting the originals, hence the leaks were forming.

I was hoping to see conical shaped particle trajectories on the other side of the hole, but thats not happening here.

I will get back to you, if i come across more doubts.

Thankyou for all your help.

Akash

Hello Akash:

  I've looked at your file and Marton's modification. I realized that the way Marton has defined the two middle facets with holes is such that the one on the bottom faces up, instead of down. You can reverse its normal by selecting it and pressing Ctrl-N (or using the equivalent command "Swap normal" in the "Facet" menu.  

  Whenever you define a facet with a hole by using the "Create two facets..." "Difference" in the "Facet" menu you should always check that the normal vector points in the direction you want, and not the reversed one. This is because the normal depends, I think... Marton correct me if I/m wrong, from the way thetwo initial facets are defined, and which vertices are chosen as the 3 first vertices in the definition of the facet with hole.

  You don't see the "conical shaped particle trajectories" because the sticking coefficient of your pumping facet is very low (a bit more than 0.03), and therefore the molecules have a large probability to travel in all directions, and even come back to the upper half of the system.

  If you change the sticking to 1, equivalent to a pump of almost 1000 l/s instead of the 30 l/s you've set, then you can see the shape of the molecules passing through the circular hole.

  Note that since your source of the molecules is the small rectangular facet on top of the system, and it faces the hole in the middle at a small distance from it, the angular distribution of the molecules going through the hole is not a cosine-like shape, but rather it has a peak at small angles... i.e. an "excess" of trajectories with directions close to the axis of the system (Y axis).

  In order to visualize this, I have set all facets to texture at 1 mm texture size (i.e. Resolution=10), and set to angular profile the two transparent facets representing the hole's entrance and exit. I have reversed their normal vector upwards. In the screenshot you can see the angular profile calculated on them, and you can see that there is an "excess" towards small angles, a bump in the curves which should otherwise resemble a sine function (because the "surface to volume" conversion box has not been checked).

  By setting the min and max value in the texture scaling pane I can visualize the varying impingement rate across the pumping facet, you can see that there is a circular area in the middle getting more hits than the peripheral area near the walls of the cylinder.

  Here is the screenshot, in dropbox, faster for me to do it like this:

  https://www.dropbox.com/s/n0wbg25gz2z8499/Akhash.JPG?dl=0

  Cheers,

   Roberto

Hello Roberto Sir,

Thankyou for your time and your reply in a detailed manner.

I am very new to this software, hence am trying to understand how to model and extract the results out of it.

Your detailed reply, helped me to understand little better than last time.

Thanks,

Akash