The Reynolds equations are still a riddle. They are based on the Navier-Stokes equations, which are still a mystery. The Navier-Stokes equations are a viscous regularization of the Euler equations, which are still an enigma. Turbulence is a riddle wrapped in a mystery inside an enigma.

~Constatin, P. “Euler equations, NSE and turbulence,” Mathematical Foundations of Turbulent Viscous Flows, Lecture notes in mathematics, 2006.¬†pp. 1-43