2025-09-19 バッファロー大学
Researchers used a turbulence chamber, above, to test their hypothesis. Credit: Douglas Levere, University at Buffalo.
＜関連情報＞
- https://www.buffalo.edu/news/releases/2025/09/particle-cluster-electrostatic-forces.html
- https://www.pnas.org/doi/abs/10.1073/pnas.2507580122
等方性乱流における接触帯電による粒子衝突の増幅 Amplification of particle collision through contact electrification in isotropic turbulence
Danielle R. Johnson, Adam Bocanski, Emily M. Diorio, +1 , and Hui Meng
Proceedings of the National Academy of Sciences Published:September 16, 2025
DOI:https://doi.org/10.1073/pnas.2507580122
Significance
Tiny particles in turbulent flows-like those in the atmosphere, drug manufacturing, or engines- often cluster more than predicted. Scientists suspected a hidden process at play. Our research reveals that when particles collide, they pick up tiny, uneven electric charges on their surfaces, despite their net neutral charge. These charges create attractive forces, pulling particles closer and increasing clustering over time. Using advanced imaging tools, we tracked particles in turbulent lab experiments and measured how their charges and movements change with time. This finding uncovers a previously overlooked mechanism in particulate turbulence, with broad implications. Better modeling of these effects could improve predictions for air pollution, weather patterns, or fuel combustion in engines-where tiny particle interactions have big impacts.
Abstract
Recent discovery of “extreme clustering” of inertial particles in isotropic turbulent flow suggests a hidden mechanism of particle–particle interaction at sub-Kolmogorov separations unexplained by hydrodynamic interaction. The near-contact radial distribution function (RDF) reaches , resulting in a collision kernel four orders larger than direct numerical simulation predictions. Statistical stationarity is lost in the particle-laden turbulence, suggesting the particles experience a nonequilibrium process. We hypothesize dielectric particles in isotropic turbulence experience contact electrification through interparticle collisions, creating inhomogeneous mosaic surface charge. These mosaic charges lead to attractive forces and thereby extreme clustering and collision amplification, forming a positive feedback loop. To explore this potential mechanism, we investigated hollow glass spheres dispersed in a high-Reynolds-number homogeneous isotropic air turbulence chamber using high-resolution 3D particle tracking velocimetry and Kelvin Probe Force Microscopy (KPFM). We measured RDF, particle-pair mean-inward radial relative velocity, and mean radial relative acceleration (RA) with time up to 10 min. We sampled particles from the flow chamber through time and evaluated their nanoscopic charge distribution using KPFM. We found that both RDF and mosaic surface charge increase with time; RA at close separations is attractive, intensifies as particles approach, and grows in time; and the turbulence-exposed RA curves collapse when nondimensionalized by the dipole–dipole acceleration calculated from mosaic charge distributions. These results support the proposed mechanism—Inhomogeneous Mosaic Potential Amplified Collisions in Turbulence (IMPACT). Better understanding and modeling of these effects could improve predictions for air pollution, weather patterns, and drug manufacturing—where particle interactions have big impacts.
