A circle swimmer at low Reynolds number

Area of Science:

• Fluid dynamics
• Microswimmers
• Theoretical physics

Background:

• Circular motion is observed in various microswimmer scenarios at low Reynolds numbers.
• Existing models, like linear swimmers, provide a basis for understanding microscale locomotion.

Purpose of the Study:

• To propose and analyze a simple model for a microswimmer exhibiting circular motion.
• To generalize previous models of linear swimmers to a triangular configuration.

Main Methods:

• Development of a theoretical model comprising three spheres in a triangular arrangement with time-dependent link lengths.
• Analysis of swimmer motion for small strokes as a function of the separation angle between links.
• Investigation of the far flow field decay characteristics.

Main Results:

• The triangular swimmer demonstrates both clockwise and anticlockwise circular motion.
• The direction of rotation is found to depend non-trivially on the tilting angle.
• The swimmer's symmetry results in a quadrupolar decay of the far flow field.

Conclusions:

• The proposed triangular swimmer model offers a new perspective on circular locomotion at low Reynolds numbers.
• The findings highlight a complex relationship between swimmer geometry, tilting angle, and rotational direction.
• Potential for experimental realization and further extensions of the model are discussed.