02-03-14, 03:32 PM
(02-03-14, 07:57 AM)mr self destruct link Wrote: Exhaust pipes are circular for a number of reasons. Mainly ease of manufacturing because its far easier to bend a round pipe than an oval one, with its strength being the same in all directions it's less likely to collapse or kink. Another reason is that a circle has the smallest edge for a given surface area*, so any other shape will add to weight and material costs. Also, a circular design minimises turbulence and disruption to the gas flow.
*for example, for a surface area of 100sqcm, a circle will have a circumference of 35.45cm, a square has edges totalling 40cm (13% more), and a right isosceles triangle will have edges totalling 48.28cm (36% more).
That makes sense.
30+ years ago I was on a geography field trip in Devon and measured the speed of water down the river Dart by standing in the river with meter, in March. Although the gradient was less, the average speed of the water was quickest lower down the river where it was deepest with less drag off the river bed.
So guess a round pipe would get rid of the exhaust gases quicker as there would be less drag from the sides of the pipe. In an oval pipe, the centre of the pipe would be closer to the pipe side, so more drag.