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Inertial Screening in SedimentationUsing particle image velocimetry we have measured the sedimentation dynamics of non-Brownian spheres over a wide range of Reynolds numbers (Re) between 0.001 and 2.5. Particle velocity fluctuations about the mean settling velocity show large-scale correlations whose spatial extent and magnitude Delta V/V are independent of Re up to a critical value Re less than Re(sub c). For Re greater than Re(sub c) the fluctuations substantially diminish with increasing Reynolds number due to inertial screening of the long-range hydrodynamic interactions (HI). The onset of inertial affects is found to occur when the Oseen length l(sub o)=v/V becomes of order the correlation length. In the inertial regime, the velocity fluctuations follow -(Delta V/V)(sup 2) approaching ln(Re), in agreement with an integration of the (l/r) HI over a narrow region extending up to the Oseen length l(sub o). A simple "blob" model connects the measured correlation lengths to the magnitudes of the velocity fluctuations.
Document ID
20020020366
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Segre, P. N.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Curreri, Peter A.
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Physics (General)
Meeting Information
Meeting: APS Division of Fluid Dynamics 54th Meeting
Location: San Diego, CA
Country: United States
Start Date: November 18, 2001
End Date: November 20, 2001
Sponsors: American Physical Society
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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