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Turbulent particle flux to a perfectly absorbing surface

Published online by Cambridge University Press:  21 June 2005

J. MANN
Affiliation:
Risø National Laboratory, DK-4000 Roskilde, Denmark
S. OTT
Affiliation:
Risø National Laboratory, DK-4000 Roskilde, Denmark
H. L. PÉCSELI
Affiliation:
University of Oslo, Institute of Physics, Box 1048 Blindern, N-0316 Oslo, Norway Centre for Advanced Study, Drammensveien 78, N-0271 Oslo, Norway
J. TRULSEN
Affiliation:
Centre for Advanced Study, Drammensveien 78, N-0271 Oslo, Norway University of Oslo, Institute of Theoretical Astrophysics, Box 1029 Blindern, N-0315 Oslo, Norway

Abstract

The feasibility of an experimental method for investigations of the particle flux to an absorbing surface in turbulent flows is demonstrated in a Lagrangian as well as an Eulerian representation. A laboratory experiment is carried out, where an approximately homogeneous and isotropic turbulent flow is generated by two moving grids. The simultaneous trajectories of many small approximately neutrally buoyant polystyrene particles are followed in time. In a Lagrangian analysis, we select one of these as the centre of a ‘sphere of interception’, and obtain estimates for the time variation of the statistical average of the inward particle flux through the surface of this moving sphere. The variation of the flux with the radius in the sphere of interception, as well as the variation with basic flow parameters is described well by a simple model, in particular for radii smaller than a characteristic length scale for the turbulence. The Eulerian counterpart of the problem is analysed as well, and the two results compared. Applications of the problem to, for instance, the question of the feeding rate of micro-organisms in turbulent marine environments are pointed out.

Type
Papers
Copyright
© 2005 Cambridge University Press

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