Tracking particles in Poiseuille flow for several pipe diameters in three dimensions
Keywords:PTV, inertial migration, large particle suspension, helical motion, instability
A setup is devised to track suspended particles in a pipe in three-dimensional space using the ShadowgraphyPTV technique. This system consists of a single camera and a mirror, and is used to track particles for over 20 pipe diameters at three downstream locations. Pipe to particle diameter ratios (D/d) of 18, 9, and 6 are investigated. The bulk Reynolds number is varied between Reb = 300-1250. As expected, particles are observed to migrate radially to a location corresponding to the Segre-Silberberg annulus. In addition, ´we observe particles also moving in the azimuthal direction (clockwise or counter-clockwise), with some particles moving as much as 180◦ during their passage through the field of view. This helical motion persists throughout the pipe (600D long) and the azimuthal velocity increases with the Reynolds number (Reb). The effect of particle size and the Reynolds number on this previously undocumented, three-dimensional motion is studied.
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