Regensburg 2019 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 38: Microswimmers (joint session DY/CPP)
DY 38.8: Talk
Wednesday, April 3, 2019, 17:30–17:45, H19
Efficiency limits of the three-sphere swimmer in viscous fluids — •Babak Nasouri1, Andrej Vilfan1,2, and Ramin Golestanian1,3 — 1Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Germany — 2J. Stefan Institute, Ljubljana, Slovenia — 3Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford, United Kingdom
We consider a swimmer consisting of a collinear assembly of three spheres connected by two slender rods. This swimmer, as first shown by Najafi and Golestanian (Phys. Rev. E 69, 062901 2004), can propel itself forward by varying the lengths of the rods in a way that is not invariant under time reversal. Although any non-reciprocal strokes of the arms can lead to a net displacement, the energetic efficiency of the swimmer is strongly dependent on the details and sequences of these strokes. We define the efficiency of the swimmer using Lighthill's criterion, i.e., the power that is needed to pull the swimmer by an external force at a certain speed, divided by the power needed for active swimming with the same average speed. Here, we determine numerically the optimal stroke sequences while limiting the maximum extension of the rods. Our calculation takes into account both far-field and near-field hydrodynamic interactions. We specifically show that the swimming efficiency initially rises by increasing the maximum allowable extension of the rods, and then converges to a maximum value.