Time persistency of floating particle clusters in free-surface turbulence

Abstract

We study the dispersion of light particles floating on a flat shear-free surface of an open channel in which the flow is turbulent. This configuration mimics the motion of buoyant matter (e.g. phytoplankton, pollutants or nutrients) in water bodies when surface waves and ripples are smooth or absent. We perform direct numerical simulation of turbulence coupled with Lagrangian particle tracking, considering different values of the shear Reynolds number (Reτ = 171 and 509) and of the Stokes number (0.06 < St < 1 in viscous units). Results show that particle buoyancy induces clusters that evolve towards a long-term fractal distribution in a time much longer than the Lagrangian integral fluid time scale, indicating that such clusters over-live the surface turbulent structures which produced them. We quantify cluster dynamics, crucial when modeling dispersion in free-surface flow turbulence, via the time evolution of the cluster correlation dimension.

References in corpus (2)

• Power-law distributions of particle concentration in free-surface flows
• Time-Evolution of a Fractal Distribution: Particle Concentrations in Free-Surface Turbulence

Cited by in corpus (5)

• Statistical models for spatial patterns of heavy particles in turbulence
• Faraday-waves contact-line shear gradient induces streaming flow and tracers' self-organization: from rotating rings to spiral galaxy-like patterns
• Mixing and unmixing induced by active camphor particles
• Small-scale dynamics and structure of free-surface turbulence
• Weak-strong clustering transition in renewing compressible flows