Kármán–Howarth equation

The Kármán–Howarth equation describes how energy flows and spreads among different sizes of swirling motions (eddies) in turbulent fluids, like water or air. It relates the changes in energy between larger and smaller eddies over distance to the rate at which energy is dissipated as heat. Essentially, it helps us understand how turbulence transports and transforms energy across scales, providing a mathematical framework to study complex fluid behaviors in natural and engineering systems.