air flow in a riffled tube

[crashforce]

evening all, im hoping some here can help. witout the use of cad for the moment im trying to calculate what happens to the air flow in a rifled barrell with regards to the rifling. i.e does the air closest to the wall corkscrew with the rifling, does the entire volume corkscrew? do the centrifugal forces leave a vaccum in the centre of the barrell?

i know im asking a lot and i dont expect it doing for me but if anyone can help it would be gratefully recieved. the variables are huge (pressure from atmospheric to 200 bar, air speed from still to subsonic etc)
so for arguements sake if we go for the top end of the pressure and just below the speed of sound and low pressure and just below the speed of sound.
thanks,
harry

 

[IRstuff]

Are you refering specifically to an internal ballistics problem? If so, then there's certainly some swirling immediately aft of the projectile, since its angular momentum must be conserved.

However, overall, there's probably little in the way of vortexing, since the primary pressure wave travels forward down the center of the barrel, as one ought to expect that the velocity immediately next to the wall must tend to zero due to aerodynamic drag.

TTFN

FAQ731-376