The effect of particle density on collisions between sinking particles: implications for particle aggregation in the ocean

摘要: Abstract A theory developed by Wacholder and Sather (1974, Journal of Fluid Mechanics, 65, 417–437) for impermeable spheres moving at low Reynolds numbers predicts that the likelihood collision between two sinking particles different size may be essentially zero if larger one settles faster but is less dense than smaller. When ratios settling velocity excess density exceed critical values determined theory, trajectory small particle closed in a region finite surrounding large particle. Small overtaken as it sinks are deflected around this collisions impossible. These findings confirmed laboratory experiments utilizing model viscous fluid. review measured rates densities marine indicates substantial fraction oceanic water column with respect to other within factor 10 or so size. Thus, aggregation differential sedimentation probably significant only very particles, which effect porosity must also considered.