Laminar parabolic flow vs turbulent chaos as Re crosses ~2300
The Reynolds number Re = rho*v*D/mu governs the laminar-to-turbulent transition. Below Re~2300 flow is laminar with parabolic Hagen-Poiseuille profile. Above ~4000 it is fully turbulent following a 1/7-power-law. The transition zone features intermittent puffs of turbulence breaking streaklines.