Century-old turbulence theory confirmed in bubble swarm experiments

An international research team from Helmholtz-Zentrum Dresden-Rossendorf, Johns Hopkins University, and Duke University has experimentally confirmed a century-old turbulence theory proposed by Soviet mathematician Andrey Kolmogorov in 1941. Kolmogorov’s theory, known as K41 scaling, describes how energy cascades from large to small scales in turbulent flows. Using advanced 3D Lagrangian tracking and high-speed cameras capturing bubble swarms rising in a water column, the researchers provided the first direct evidence that bubble-induced turbulence follows Kolmogorov scaling at small scales, particularly for eddies smaller than the bubbles themselves. The experiments involved varying bubble sizes (3-5 mm) and gas densities in a controlled vertical water column, revealing that turbulence outside the immediate wakes of bubbles adheres closely to Kolmogorov’s predictions. The wakes themselves disrupt the flow structure, explaining why previous studies failed to detect this scaling in bubbly flows. The team also developed a new formula to estimate energy