Why smooth walls?

[Allen-in-Sheboygan]

If the point of the DC is to slow down the air so particles will drop out, wouldn't a rough inner surface be a good thing?  I am wondering if attaching a very course sandpaper to the lower half of the inner wall would be a good thing as it would slow the air just above the baffle slot.

Aside: has there been any though given to putting "deswirl" vanes below the baffle to minimize disturbing the already separated dust?

[Allen-in-Sheboygan]

I'd like to elaborate (taken from another thread): :-\

Regarding thy physical process of separation, I would like to know more myself as that knowledge should lead to design improvements.
My take so far is:
Step one: Particles are moved to the outer diameter of the separator by centrifugal action as the air swirls around in the separator.  This air flow should be smooth (laminar) as turbulence will tend to re-mix the particles into the air stream.
Step two:  Once the particles have reached the outer wall, friction slows them down and they fall toward the outlet at the bottom of the separator (i.e. through the slot in the baffle in our case).

If the above is correct, I would think that a smooth outer wall would improve the cyclonic separation until the particles reach the wall.  From then on, a rough wall (course sandpaper, perhaps) would enhance the slowing down process.

I have also thought that slots placed in the lower outer wall would help remove the outer few mm of the air stream that contains the particles.  Obviously, the slotted portion of the separator would have to protrude into the collecting bucket.  This would not require the particles to "fall" out of the air stream which to me would seem to improve small particle separation - think of how dust "hangs" in the air and takes minutes to settle out compared to fractions of a second available to "fall" out in the separator.

[phil (admin)]

If you want to go after the finest dust, you won't find it at the wall.  So sandpaper and slats won't help you, I'm afraid.