Slightly random question but anyway.....

 

As a keen shisha pipe collector I spend a lot of my evenings practicing blowing smoke rings while I watch tv. Recently I've been wondering whether it would be possible to create other shapes i.e. stars or triangles and experimented with making hollow shaped tubes to see if I could make any. As expected it didn't really work.

 

Why is this? Is there a reason why rings seem so stable or are other shapes possible? What do you think?

it's to do with the flow around objects, smoke rings are formed by flow around a sphere, so it might be possible to create other shapes but it's probably a better option to put something in the flow not just the tube shape.

 

The size of the tube, object and the fluid flow will also make a difference...

I've done a couple of experiments and witnessed a crazy man at my University doing several mosre with vortex rings. Although they've only been circular ones, from what I've seen. I'd suggest using a triangular,star or whatever you like shaped rod and moving it quickly through a slightly larger chamber filled with smoke.