An elementary example of contrasting laminar and turbulent flow physics

Abstract

Something as simple as Couette and Poiseuille onedimensional flow of a newtonian fluid between infinite parallel walls provides an illuminating example of the contrasting physics of laminar and turbulent flow: the difference between their mean velocity profiles has in one regime the opposite sign than in the other. This easily verifiable but yet unnoticed behaviour implies that the physical mechanisms of laminar and turbulent transport are even more fundamentally different than ordinarily presumed.