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Lookup NU author(s): Emeritus Professor Mike Reeks
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DNS studies of dispersed particle motion in isotropic homogeneous turbulence  have revealed the existence of a component of random uncorrelated motion (RUM) dependent on the particle inertia τP (normalised particle response time or Stoke number). This paper reports the presence of RUM in a simple linear random smoothly varying flow field of counter rotating vortices where the two-particle velocity correlation was measured as a function of spatial separation.Values of the correlation less than one for zero separation indicated the presence of RUM. In terms of Stokes number, the motion of the particles in one direction corresponds to either a heavily damped (τP < 0.25) or lightly damped (τP > 0.25) harmonic oscillator. In the lightly damped case the particles overshoot the stagnation lines of the flow and are projected from one vortex to another (the so-called sling-shot effect). It is shown that RUM occurs only when τp > 0.25, increasing monotonically with increasing Stokes number. Calculations of the particle pair separation distribution function show that equilibrium of the particle concentration field is never reached, the concentration at zero separation increasing monotonically with time. This is consistent with the calculated negative values of the average Liapounov exponent (finite compressibility) of the particle velocity field. Copyright © 2006 by ASME.
Author(s): Reeks MW, Fabbro L, Soldati A
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: ASME 2006 2nd Joint US-European Fluids Engineering Summer Meeting (FEDSM 2006)
Year of Conference: 2006
Publisher: American Society of Mechanical Engineers, US
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