Experimental study of gravity-driven dense suspension jets

This article presents experimental results from a study of a jet of dense suspension falling under gravity in a quiescent liquid bath of miscible liquid. The initial jet velocity v(0) scales with the square of the initial jet diameter. Four different flow behaviors are observed. The jet remains cylindrical and stable when viscous forces are dominant. A capillary-like instability with formation of blobs occurs when a Reynolds number based on the particle diameter and a free-falling velocity is over unity. The blobs are stable and settle without changing shape only for a blob Reynolds number below a critical number. Dispersion of the jet particles is observed when the particle Reynolds number is over 1, and an atomization behavior occurs when particle inertia is large compared to viscous forces, i.e., when the Stokes number of the particles is large compared to unity. (C) 2002 American Institute of Physics.