Nonlinear flow response of soft hair beds

Alvarado, José; Comtet, Jean; Langre, Emmanuel de; Hosoi, A. E.

doi:10.1038/nphys4225

Cited by 50 publications

(71 citation statements)

References 39 publications

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“…Figure 9d (top right) shows the model's result in simulating a soft flow rectifiern by the bending of a bed of tilted and anchored elastic fibers (Fig. 9d (top middle) from [1]).…”

Section: Discussionmentioning

confidence: 99%

“…Detailed theoretical descriptions are still few, and a full accounting is beyond the scope of our review, but we discuss several interesting recent examples. [1] have recently shown how to construct soft flow rectifiers by mounting dense beds of tilted flexible fibers onto the walls of a flow channel (Fig. 9d, right panel).…”

Section: B Sedimentation Of Fiber Assembliesmentioning

confidence: 99%

See 1 more Smart Citation

Dynamics of Flexible Fibers in Viscous Flows and Fluids

Roure

Lindner

Nazockdast

et al. 2019

Annu. Rev. Fluid Mech.

177

156

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The dynamics and deformations of immersed flexible fibers are at the heart of important industrial and biological processes, induce peculiar mechanical and transport properties in the fluids that contain them, and are the basis for novel methods of flow control. Here we focus on the low Reynolds number regime where advances in studying these fiber-fluid systems have been especially rapid. On the experimental side this is due to new methods of fiber synthesis, microfluidic flow control, and of microscope based tracking measurement techniques. Likewise, there have been continuous improvements in the specialized mathematical modeling and numerical methods needed to capture the interactions of slender flexible fibers with flows, boundaries, and each other. arXiv:1905.09058v1 [physics.flu-dyn]

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“…Figure 9d (top right) shows the model's result in simulating a soft flow rectifiern by the bending of a bed of tilted and anchored elastic fibers (Fig. 9d (top middle) from [1]).…”

Section: Discussionmentioning

confidence: 99%

Section: B Sedimentation Of Fiber Assembliesmentioning

confidence: 99%

Dynamics of Flexible Fibers in Viscous Flows and Fluids

Roure

Lindner

Nazockdast

et al. 2019

Annu. Rev. Fluid Mech.

177

156

View full text Add to dashboard Cite

show abstract

“…In Section IV, we see that beds of fibers deform and inhibit flow in response to an imposed shear in a manner that depends on the fiber bed density. It has been recently observed [1] that this may be exploited for flow rectification by angling the beds with respect to the channel. In this section we examine this problem in detail, with a focus on optimizing flow rectification.…”

Section: Modeling a Soft Rectifiermentioning

confidence: 99%

“…Another example is the beds of driven cilia that pump fluid, move mucus, or propel microorganisms [4]. In microfluidic engineering, fabricated arrays of flexible fibers are the elements of proposed soft flow rectifiers [1]. A central aspect of all of these examples is that the relevant dynamics is collective and not well-described by the dynamics of a single fiber.Given the importance of fluid-fiber systems, specialized computational methods have been developed to treat them, most especially in the zero Reynolds limit where flows are governed by the Stokes equation.…”

mentioning

confidence: 99%

Coarse graining the dynamics of immersed and driven fiber assemblies

Stein

Shelley

2019

Phys. Rev. Fluids

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An important class of fluid-structure problems involve the dynamics of ordered arrays of immersed, flexible fibers. While specialized numerical methods have been developed to study fluid-fiber systems, they become infeasible when there are many, rather than a few, fibers present, nor do these methods lend themselves to analytical calculation. Here, we introduce a coarse-grained continuum model, based on local-slender body theory, for elastic fibers immersed in a viscous Newtonian fluid. It takes the form of an anisotropic Brinkman equation whose skeletal drag is coupled to elastic forces. This model has two significant benefits: (1) the density effects of the fibers in a suspension become analytically manifest, and (2) it allows for the rapid simulation of dense suspensions of fibers in regimes inaccessible to standard methods. As a first validation, without fitting parameters, we achieve very reasonable agreement with 3D Immersed Boundary simulations of a bed of anchored fibers bent by a shear flow. Secondly, we characterize the effect of density on the relaxation time of fiber beds under oscillatory shear, and find close agreement to results from full numerical simulations. We then study buckling instabilities in beds of fibers, using our model both numerically and analytically to understand the role of fiber density and the structure of buckling transitions. We next apply our model to study the flow-induced bending of inclined fibers in a channel, as has been recently studied as a flow rectifier, examining the nature of the internal flows within the bed, and the emergence of inhomogeneous permeability. Finally, we extend the method to study a simple model of metachronal waves on beds of actuated fibers, as a model for ciliary beds. Our simulations reproduce qualitatively the pumping action of coordinated waves of compression through the bed. I. INTRODUCTIONMany fundamental hydrodynamic phenomena, particularly in biology, involve the interaction of structured arrays of immersed fibers, often anchored to a substrate [21]. For example, in eukaryotic cells, arrays of aligned microtubules in the spindle orchestrate the segregation of chromosomes, while those around centrosomes help position the spindle prior to cell division [14]. During midoogenesis of Drosophila, kinesin motors interacting with the microtubule cytoskeleton drive largescale coherent flows known as cytoplasmic streaming [10]. Another example is the beds of driven cilia that pump fluid, move mucus, or propel microorganisms [4]. In microfluidic engineering, fabricated arrays of flexible fibers are the elements of proposed soft flow rectifiers [1]. A central aspect of all of these examples is that the relevant dynamics is collective and not well-described by the dynamics of a single fiber.Given the importance of fluid-fiber systems, specialized computational methods have been developed to treat them, most especially in the zero Reynolds limit where flows are governed by the Stokes equation. These approaches include the use of nonlocal slender body the...

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“…Micro-organisms interact with biological flows which are often viscoelastic and always at low Reynolds numbers 10,36 . Mimicing of micro-organisms using bio-inspired cilia and flagella has applications in the development of artifical micro-swimmers, micropumps, valves and mixers [37][38][39] . Our study of thin cantilevered micro-scale beams placed in viscoelastic flow could help in understanding the dynamics and interactions of micro-organisms in a host of different micro-environments.…”

Section: Introductionmentioning

confidence: 99%

Oscillations of a cantilevered micro beam driven by a viscoelastic flow instability

et al. 2020

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The interaction of flexible structures with viscoelastic flows can result in very rich dynamics. In this paper, we present the results of the interactions between the flow of a viscoelastic polymer solution and a cantilevered beam in a confined microfluidic geometry. Cantilevered beams with varying length and flexibility were studied. With increasing flow rate and Weissenberg number, the flow transitioned from a fore-aft symmetric flow to a stable detached vortex upstream of the beam, to a time-dependent unstable vortex shedding. The shedding of the unstable vortex upstream of the beam imposed a time-dependent drag force on the cantilevered beam resulting in flow-induced beam oscillations. The oscillations of the flexible beam were classified into two distinct regimes: a regime with a clear single vortex shedding from upstream of the beam resulting in a sinusoidal beam oscillation pattern with the frequency of oscillation increasing monotonically with Weissenberg number, and a regime at high Weissenberg numbers characterized by 3D chaotic flow instabilities where the frequency of oscillations plateaued. The critical onset of the flow transitions, the mechanism of vortex shedding and the dynamics of the cantilevered beam response are presented in detail here as a function of beam flexibility and flow viscoelasticity.Alternatively, allowing these instabilities to affect the position, deformation and motion of an object falls in the domain of fluidstructure interaction problems and introduces a host of interesting questions regarding the dynamics and elasticity of the struc-J o u r n a l N a me , [ y e a r ] , [ v o l . ] , 1-8 | 1 arXiv:1910.04203v1 [physics.flu-dyn] 9 Oct 2019A second set of experiments was conducted where the flexible Beam 1 was replaced with a more flexible beam, Beam 2 (see details in Table 1) which had the same beam width and elastic modulus but a longer beam length while maintaining a similar chan-J o u r n a l N a me , [ y e a r ] , [ v o l . ] , 1-8 | 5

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Nonlinear flow response of soft hair beds

Cited by 50 publications

References 39 publications

Dynamics of Flexible Fibers in Viscous Flows and Fluids

Dynamics of Flexible Fibers in Viscous Flows and Fluids

Coarse graining the dynamics of immersed and driven fiber assemblies

Oscillations of a cantilevered micro beam driven by a viscoelastic flow instability

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