Originally Posted by rmfnla
FWIW, flutes are an engineering trick to make tubes stiffer while reducing weight.
A good example of this is match-grade rifle barrels (for them, the additional surface area of the flutes also facilitates cooling, not an issue for most riders).
Another $0.02 worth...
Another example is the "blood groove" in a hunting or fighting knife. Contrary to popular belief, it has nothing to do with relieving suction by allowing blood to flow, and everything to do with stiffness. Like an I-beam.