Self-propulsion of a freely suspended swimmer by a swirling tail in a viscoelastic fluid

Binagia, Jeremy P.; Shaqfeh, Eric S. G.

doi:10.1103/physrevfluids.6.053301

Cited by 32 publications

(52 citation statements)

References 34 publications

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“…The propulsion mechanism of this device is directly related to the first normal stress coefficient, as predicted in previous theoretical work [15]. This is further supported by the experimental observation that the swimmer cannot propel itself in Newtonian, non-elastic fluids at low Reynolds numbers.…”

Section: Propulsion Mechanismsupporting

confidence: 85%

“…While we defer the detailed derivation of the asymptotic theory and numerical simulations to the Methods section (section A) and prior work (i.e. [15]), we briefly summarize them below. To model the motion of our robotic swimmer via theory and numerical simulations, we adopt the model illustrated in fig.…”

Section: Summary Of Asymptotic Theory and Numerical Simulationsmentioning

confidence: 99%

“…that the swimmer is net force and torque free [9]) both numerically and through a far-field asymptotic theory valid for small De. The details of the numerical solution methodology are listed in section D and prior work ( [15]). In brief, the numerical solution considers the co-moving frame of reference such that a body-fitted mesh may be considered around the swimmer (with increasing mesh resolution in the vicinity of the swimmer).…”

Section: Summary Of Asymptotic Theory and Numerical Simulationsmentioning

confidence: 99%

“…Alongside our numerical solution is a far-field asymptotic analysis valid for small De. The details may be found in section B and Binagia and Shaqfeh [15], while the key results are summarized below. It is shown using a far-field asymptotic analysis in section B that for small De the speed of the swimmer is of the general form:…”

Section: Summary Of Asymptotic Theory and Numerical Simulationsmentioning

confidence: 99%

“…Significant flow in the azimuthal direction (i.e. around the spinning tail) is also visable as dark strands around the small sphere; such flow is predicted to generate regions of large hoop stress around the tail of the swimmer [15].…”

Section: Propulsion Mechanismmentioning

confidence: 99%

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A Swimming Rheometer: Self-propulsion of a freely-suspended swimmer enabled by viscoelastic normal stresses

Kroo¹,

Binagia²,

Eckman³

et al. 2021

Preprint

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Self-propulsion at low Reynolds number is notoriously restricted, a concept that is commonly known as the "scallop theorem". Here we present a truly self-propelled swimmer (force-and torquefree) that, while unable to swim in a Newtonian fluid due to the scallop theorem, propels itself in a non-Newtonian fluid as a result of fluid elasticity. This propulsion mechanism is demonstrated using a robotic swimmer, comprised of a "head" sphere and a "tail" sphere, whose swimming speed is shown to have reasonable agreement with a microhydrodynamic asymptotic theory and numerical simulations. Schlieren imaging demonstrates that propulsion of the swimmer is driven by a strong viscoelastic jet at the tail, which develops due to the fore-aft asymmetry of the swimmer. Optimized cylindrical and conic tail geometries are shown to double the propulsive signal, relative to the optimal spherical tail. Finally, we show that we can use observations of this robot to infer rheological properties of the surrounding fluid. We measure the primary normal stress coefficient, Ψ1 at shear rates < 1 Hz, and show reasonable agreement with extrapolated bench-top measurements (between 0.8 − 1.2 Pa sec 2 difference).We also discuss how our swimmer can be used to measure the second normal stress coefficient, Ψ2, and other rheological properties. The study experimentally demonstrates the exciting potential for a "swimming rheometer", bringing passive physics-driven fluid sensing to numerous applications in chemical and bioengineering.

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Section: Propulsion Mechanismsupporting

confidence: 85%

Section: Summary Of Asymptotic Theory and Numerical Simulationsmentioning

confidence: 99%

Section: Summary Of Asymptotic Theory and Numerical Simulationsmentioning

confidence: 99%

Section: Summary Of Asymptotic Theory and Numerical Simulationsmentioning

confidence: 99%

Section: Propulsion Mechanismmentioning

confidence: 99%

See 3 more Smart Citations

A Swimming Rheometer: Self-propulsion of a freely-suspended swimmer enabled by viscoelastic normal stresses

Kroo¹,

Binagia²,

Eckman³

et al. 2021

Preprint

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Propulsion efficiency of achiral microswimmers in viscoelastic polymer fluids

et al. 2022

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We report the effects of polymer size, concentration, and polymer fluid viscoelasticity on the propulsion kinematics of achiral microswimmers. Magnetically driven swimmer's step-out frequency, orientation angle, and propulsion efficiency are shown to be dependent on fluid microstructure, viscosity, and viscoelasticity. Additionally, by exploring the swimming dynamics of two geometrically distinct achiral structures, we observe differences in propulsion efficiencies of swimmers. Results indicate that larger four-bead swimmers are more efficiently propelled in fluids with significant elasticity in contrast to smaller 3-bead swimmers, which are able to use shear thinning behavior for efficient propulsion. Insights gained from these investigations will assist the development of future microswimmer designs and control strategies targeting applications in complex fluids.

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Microswimming in viscoelastic fluids

Lauga

Ardekani

2021

Journal of Non-Newtonian Fluid Mechanics

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Self-propulsion of a freely suspended swimmer by a swirling tail in a viscoelastic fluid

Cited by 32 publications

References 34 publications

A Swimming Rheometer: Self-propulsion of a freely-suspended swimmer enabled by viscoelastic normal stresses

A Swimming Rheometer: Self-propulsion of a freely-suspended swimmer enabled by viscoelastic normal stresses

Propulsion efficiency of achiral microswimmers in viscoelastic polymer fluids

Microswimming in viscoelastic fluids

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