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Title: On the relative rotational motion between rigid fibers and fluid in turbulent channel flow

In this study, the rotation of small rigid fibers relative to the surrounding fluid in wall-bounded turbulence is examined by means of direct numerical simulations coupled with Lagrangian tracking. Statistics of the relative (fiber-to-fluid) angular velocity, referred to as slip spin in the present study, are evaluated by modelling fibers as prolate spheroidal particles with Stokes number, St, ranging from 1 to 100 and aspect ratio, λ, ranging from 3 to 50. Results are compared one-to-one with those obtained for spherical particles (λ = 1) to highlight effects due to fiber length. The statistical moments of the slip spin show that differences in the rotation rate of fibers and fluid are influenced by inertia, but depend strongly also on fiber length: Departures from the spherical shape, even when small, are associated with an increase of rotational inertia and prevent fibers from passively following the surrounding fluid. An increase of fiber length, in addition, decouples the rotational dynamics of a fiber from its translational dynamics suggesting that the two motions can be modelled independently only for long enough fibers (e.g., for aspect ratios of order ten or higher in the present simulations)
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. Department of Electrical, Management and Mechanical Engineering, University of Udine, 33100 Udine (Italy)
  2. Department of Energy and Process Engineering, Norwegian University of Science and Technology, 7491 Trondheim (Norway)
  3. (Norway)
Publication Date:
OSTI Identifier:
22482484
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Fluids (1994); Journal Volume: 28; Journal Issue: 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANGULAR VELOCITY; ASPECT RATIO; COMPUTERIZED SIMULATION; FIBERS; FLUIDS; LAGRANGIAN FUNCTION; LENGTH; ROTATION; SPHERICAL CONFIGURATION; STOKES NUMBER; TURBULENCE