Regensburg 2010 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 24: Turbulence and wind energy
DY 24.9: Talk
Thursday, March 25, 2010, 12:00–12:15, H47
Finite-size effects in the dynamics of neutrally buoyant particles in turbulent flow — •Holger Homann1, Jérémie Bec2, and Rainer Grauer1 — 1Institut für Theoretische Physik I, Ruhr-Universität Bochum, 44780 Bochum — 2Laboratoire Cassiopée UMR6202 Observatoire de la Côte d'Azur BP4229, 06304 Nice Cedex 4, France
The dynamics of neutrally buoyant particles transported by a turbulent flow is investigated for spherical particles with radii of the order of the Kolmogorov dissipative scale or larger. The pseudo-penalisation spectral method that has been proposed by Pasquetti et al. (2008) is adapted to integrate numerically the simultaneous dynamics of the particle and of the fluid. Such a method gives a unique handle on the limit of validity of point-particle approximations, which are generally used in applicative situations. Analytical predictions based on such models are compared to result of very well resolved direct numerical simulations. Evidence is obtained that Faxén corrections give dominant finite-size corrections to velocity and acceleration fluctuations for particle diameters up to four times the Kolmogorov scale. The dynamics of particles with larger diameters is dominated by inertial-range physics, and is consistent with predictions obtained from dimensional analysis.