Dresden 2011 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Fluid Dynamics and Turbulence I

DY 13.1: Topical Talk

Tuesday, March 15, 2011, 10:15–10:45, ZEU 118

Aggregation and Fragmentation of fractal-like particles in synthetic turbulent flows — •Ulrike Feudel, Jens Zahnow, and Joeran Maerz — ICBM, Carl von Ossietzky University Oldenburg

Inertial particles in fluid flows are of increasing interest in different disciplines of science such as dynamical systems theory, atmospheric and marine science as well as engineering. In many cases particles are not only transported passively by advection but exhibit a dynamics of their own as they can form larger particles upon collision or can break up. Examples of particle dynamics are raindrop formation in clouds, sedimentation of particles in lakes and the ocean or flocculation of marine aggregates and cells. We present a coupled model for advection, aggregation and fragmentation that is based on the dynamics of individual, spherical and fractal-like inertial particles in synthetic turbulent flows. Due to the particle inertia advection leads to the preferential concentrations of the particles in certain spatial regions. The collision of the particles leads to aggregation and larger aggregates are formed. These can in turn fragment due to shear forces in the flow. We find that the combination of aggregation and fragmentation leads to an asymptotic steady state for the size distribution of the aggregates which depends crucially on the considered mechanism of fragmentation. We discuss the dependence of the final size distributions on the properties of the aggregates as well as of the flow.