Turbulenties

Turbulenties is a term used to describe fluid motions characterized by irregular, chaotic fluctuations in velocity and pressure. They arise when inertial forces dominate viscous forces, typically at high Reynolds numbers, and feature rapid temporal changes and intense mixing. The flow contains a wide range of interacting eddies from large energy-containing scales to small dissipative scales, in a process known as the energy cascade.

Because turbulence is complex, it is usually described statistically. Key features include anisotropy and inhomogeneity near boundaries, strong velocity fluctuations, and intermittency. The energy cascades from large to small scales until viscous dissipation converts it to heat. In many flows, velocity fluctuations exhibit a broad spectrum, with a -5/3 slope in the inertial range in line with Kolmogorov's 1941 theory.

Occurrences span nature and engineering: atmospheric and oceanic flows, rivers and clouds, combustion, aerodynamic drag, pipe and duct flows, and plasmas. Tur turbulenties are relevant for weather prediction, climate models, industrial mixing, and energy systems due to their influence on transport and reaction rates.

Modeling approaches include direct numerical simulation (DNS), which resolves all scales; large eddy simulation (LES), which models only the smallest scales; and Reynolds-averaged Navier–Stokes (RANS) methods with turbulence models such as k-epsilon or k-omega. Turbulenties remain a central challenge in fluid dynamics because of the closure problem in the governing equations.

Diagnostics used to study turbulenties include hot-wire anemometry, Laser Doppler Velocimetry (LDV), and Particle Image Velocimetry (PIV). Historically, turbulence research began with Osborne Reynolds’ pipe-flow experiments in the late 19th century and was advanced by Kolmogorov and others in the 20th century.