Generalized squirming motion of a sphere

• Published in: Journal of engineering mathematics Vol. 88; no. 1; pp. 1 - 28
• Main Authors: Pak, On Shun, Lauga, Eric
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2014
• Subjects: Applications of Mathematics; Computational Mathematics and Numerical Analysis; Mathematical and Computational Engineering; Mathematical Modeling and Industrial Mathematics; Mathematics; Mathematics and Statistics; Theoretical and Applied Mechanics; Squirming motion; Low-Reynolds-number locomotion; Stokes flows
• ISSN: 0022-0833; 1573-2703
• DOI: 10.1007/s10665-014-9690-9

A number of swimming microorganisms, such as ciliates ( Opalina ) and multicellular colonies of flagellates ( Volvox ), are approximately spherical in shape and swim using beating arrays of cilia or short flagella covering their surfaces. Their physical actuation on the fluid may be mathematically modeled as the generation of surface velocities on a continuous spherical surface—a model known in the literature as squirming, which has been used to address various aspects of the biological physics of locomotion. Previous analyses of squirming assumed axisymmetric fluid motion and hence required all swimming kinematics to take place along a line. In this paper we generalize squirming to three spatial dimensions. We derive analytically the flow field surrounding a spherical squirmer with arbitrary surface motion and use it to derive its three-dimensional translational and rotational swimming kinematics. We then use our results to physically interpret the flow field induced by the swimmer in terms of fundamental flow singularities up to terms decaying spatially as ∼ 1 / r 3 . Our results will make it possible to develop new models in biological physics, in particular in the area of hydrodynamic interactions and collective locomotion.