Self-propulsion of a submerged sphere due to coupling of its deformation and internal mass shift

Abstract

The self-propulsion of a deforming sphere through an unbounded inviscid fluid is investigated analytically. Its motion is only induced by the coupling of its radial alteration, centroid shift, and rotation of the internal masses without vortex shedding and external forces. The Lagrange equations are used to describe such self-motion since the fluid-body system is conservative. Then the expressions for translational and rotational velocities of the deforming body are obtained in algebraic forms. Several cases show that some typical moving patterns of the sphere would be obtained as long as its radius variation and internal mass shift are properly coupled.