A simple equation, the Navier–Stokes, completely describes a fluid’s flow. A single parameter, the Reynolds number, flags a flow as smooth or turbulent. But a true understanding of turbulence—one that would furnish accurate predictions of a hurricane’s path or a car’s drag—remains out of reach.
Studying small-scale eddies could bring that goal closer. Tornados and breaking waves look different from afar, but their kinetic energy ends up in the same sort of localized viscous heating. If, as fluid dynamicists suspect, small-scale eddies behave in a universal way before they dissipate, it might be possible to build up reliable predictions of large-scale behavior.
But even if one explored the smallest scales, one property of turbulence blocks the path to understanding: intermittence. In turbulent flows, violent, sporadic jumps can occur without warning. Such events, despite their rarity, can’t be ignored. A once-a-century gust of wind could be the one that blows the...
