Hydrodynamic orienting of asymmetric microobjects under gravity

Abstract

It is shown that nonsymmetric microobjects orient while settling under gravity in a viscous fluid. To analyze this process, a simple shape is chosen: a non-deformable `chain'. The chain consists of two straight arms, made of touching solid spheres. In the absence of external torques, the spheres are free to spin along the arms. The motion of the chain is evaluated by solving the Stokes equations with the use of the multipole method. It is demonstrated that the spinning beads speed up sedimentation by a small amount, and increase the orientation rate significantly in comparison to the corresponding rigid chain. It is shown that chains orient towards the V-shaped stable stationary configuration. In contrast, rods and star-shaped microobjects do not rotate. The hydrodynamic orienting is relevant for efficient swimming of non-symmetric microobjects, and for sedimenting suspensions.

9 pages

References in corpus (3)

• A Simplest Swimmer at Low Reynolds Number: Three Linked Spheres
• Numerical Study of a Microscopic Artificial Swimmer
• Symmetric three-particle motion in Stokes flow: equilibrium for heavy spheres in contrast to "end-of-world" for point forces

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• Orientation dynamics of two-dimensional concavo-convex bodies
• A Theory of Pitch for the Hydrodynamic Properties of Molecules, Helices, and Achiral Swimmers at Low Reynolds Number
• Dynamics of Mass Polar Spheroids During Sedimentation
• Dynamical modes of highly elastic loops settling under gravity in a viscous fluid