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Journal Articles Physical Review Fluids Year : 2022

Spirographic motion in a vortex

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Studies of particle motion in vortical flows have mainly focused on pointlike particles. This approximation assumes that the velocity field that surrounds the particle is linear. We consider an inertialess rigid dumbbell in a two-dimensional steady vortex. While the system remains analytically tractable, the particle experiences the nonlinearity of the surrounding velocity field. By exploiting the rotational symmetry of the flow, we reduce the problem to that of a two-dimensional dynamical system, whose fixed points and periodic orbits can be used to explain the motion of the dumbbell. For all vortices in which the fluid angular velocity decreases with radial distance, the center of mass of the dumbbell follows a spirographic-like trajectory around the vortex center. This results from a periodic oscillation in the radial direction combined with revolution around the center. The shape of the trajectory depends strongly on the initial position and orientation of the dumbbell, but the dynamics is qualitatively the same irrespective of the form of the vortex. If the fluid angular velocity is not monotonic, the spirographic-like motion is altered by the existence of transport barriers, whose shape is now sensitive to the details of the vortex. This analysis may be extended to study the dynamics of inertial and/or self-propelled dumbbells in a two-dimensional vortex.
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Dates and versions

hal-03875492 , version 1 (28-11-2022)



Sumithra Reddy Yerasi, Rama Govindarajan, Dario Vincenzi. Spirographic motion in a vortex. Physical Review Fluids, 2022, 7, pp.074402. ⟨10.1103/PhysRevFluids.7.074402⟩. ⟨hal-03875492⟩
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