Simulations of single and multiple swimmers with non-divergence free deforming geometries

Gazzola, Mattia; Chatelain, Philippe; Rees, Wim M. van; Koumoutsakos, Petros

doi:10.1016/j.jcp.2011.04.025

Cited by 162 publications

(237 citation statements)

References 57 publications

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“…16 The method solves the vorticity equation on a wavelet-adapted computational grid, using a multipole-based solver to reconstruct the velocity from the vorticity field. 17 Particles are used for the advection part of the equation; diffusion is handled with a fourth-order finite difference scheme and an explicit Runge-Kutta 2 time stepping scheme.…”

Section: B Computational Methodsmentioning

confidence: 99%

“…The method and code have been extensively used and validated for similar problems. 8,[16][17][18][19] Throughout this work, we set the effective resolution of our unit square domain to E R = 32 768 2 , and the cylinder radius equal to R = 0.0025, so that there are over 80 grid points across the radius at the maximum level of grid refinement. The refinement and compression thresholds are r tol = 10 −3 , c tol = 10 −4 , and the cylinder is represented on the computational grid through a discrete Heaviside function.…”

Section: B Computational Methodsmentioning

confidence: 99%

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Self-propulsion of a counter-rotating cylinder pair in a viscous fluid

2015

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We study a self-propelling pair of steadily counter-rotating cylinders in simulations of a two-dimensional viscous fluid. We find two strikingly, opposite directions for the motion of the pair that is characterized by its width and rotational Reynolds number. At low Reynolds numbers and large widths, the cylinder pair moves similarly to an inviscid point vortex pair, while at higher Reynolds numbers and smaller widths, the pair moves in the opposite direction through a jet-like propulsion mechanism. Increasing further the Reynolds number, or decreasing the width, gives rise to non-polarised motion governed by the shedding direction and frequency of the boundary-layer vorticity. We discuss the fundamental physical mechanisms for these two types of motion and the transitions in the corresponding phase diagram. We discuss the fluid dynamics of each regime based on streamline plots, tracer particles, and the vorticity field. The counter rotating cylinder pair serves as a prototype for self-propelled bodies and suggests possible engineering devices composed of simple components and tunable by the rotation and width of the cylinder pair. C 2015 AIP Publishing LLC. [http://dx

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Section: B Computational Methodsmentioning

confidence: 99%

Section: B Computational Methodsmentioning

confidence: 99%

Self-propulsion of a counter-rotating cylinder pair in a viscous fluid

2015

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“…Interface 13: 20160734 favoured with respect to the opposite IP mode. These two swimming modes have been studied recently both experimentally [24,25] and numerically [7] in the context of collective swimming of fish-like robots. The main conclusion of those works rsif.royalsocietypublishing.org J. R. Soc.…”

Section: ð3:2þmentioning

confidence: 99%

Synchronization and collective swimming patterns in fish (Hemigrammus bleheri)

Ashraf

Godoy-Diana

Halloy

et al. 2016

J. R. Soc. Interface.

113

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In this work, we address the case of red nose tetra fish Hemigrammus bleheri swimming in groups in a uniform flow, giving special attention to the basic interactions and cooperative swimming of a single pair of fish. We first bring evidence of synchronization of the two fish, where the swimming modes are dominated by 'out-phase' and 'in-phase' configurations. We show that the transition to this synchronization state is correlated with the swimming speed (i.e. the flow rate), and thus with the magnitude of the hydrodynamic pressure generated by the fish body during each swimming cycle. From a careful spatio-temporal analysis corresponding to those synchronized modes, we characterize the distances between the two individuals in a pair in the basic schooling pattern. We test the conclusions of the analysis of fish pairs with a second set of experiments using groups of three fish. By identifying the typical spatial configurations, we explain how the nearest neighbour interactions constitute the building blocks of collective fish swimming.

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“…The self-propelled swimmers used in the simulations are based on a simplified physical model of zebrafish as described in Gazzola et al (2011). Undulations of the swimmer's body are generated by imposing a spatially and temporally varying body curvature (k(s, t)), which passes down from the head to the tail as a sinusoidal travelling wave:…”

Section: Swimmers and Numerical Methodsmentioning

confidence: 99%

Synchronisation through learning for two self-propelled swimmers

et al. 2017

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We study the fluid dynamics of two fish-like bodies with synchronised swimming patterns. Our studies are based on two-dimensional simulations of viscous incompressible flows. We distinguish between motion patterns that are externally imposed on the swimmers and self-propelled swimmers that learn manoeuvres to achieve certain goals. Simulations of two rigid bodies executing pre-specified motion indicate that flow-mediated interactions can lead to substantial drag reduction and may even generate thrust intermittently. In turn we examine two self-propelled swimmers arranged in a leader-follower configuration, with a-priori specified body-deformations. We find that the swimming of the leader remains largely unaffected, while the follower experiences either an increase or decrease in swimming speed, depending on the initial conditions. Finally, we consider a follower that synchronises its motion so as to minimize its lateral deviations from the leader's path. The leader employs a steady gait while the follower uses a reinforcement learning algorithm to adapt its swimming-kinematics. We find that swimming in a synchronised tandem can yield up to about 30% reduction in energy expenditure for the follower, in addition to a 20% increase in its swimming-efficiency. The present results indicate that synchronised swimming of two fish can be energetically beneficial.

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Simulations of single and multiple swimmers with non-divergence free deforming geometries

Cited by 162 publications

References 57 publications

Self-propulsion of a counter-rotating cylinder pair in a viscous fluid

Self-propulsion of a counter-rotating cylinder pair in a viscous fluid

Synchronization and collective swimming patterns in fish (Hemigrammus bleheri)

Synchronisation through learning for two self-propelled swimmers

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