Passive appendages generate drift through symmetry breaking

Lācis, Uǧis; Brosse, Nicolas; Ingremeau, François; Mazzino, Andrea; Lundell, Fredrik; Kellay, Hamid; Bagheri, Shervin

doi:10.1038/ncomms6310

Cited by 52 publications

(69 citation statements)

References 26 publications

(36 reference statements)

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“…Extending work of Bagheri et al [20], Lacis et al [21] showed the symmetry-breaking instability is similar to the instability of an inverted pendulum. Note that these studies considered very low values of structure-fluid density ratio ((0.1)) as well as flexural rigidity ((0.001)-(0.1)), which is two-three orders of magnitude lesser than the values used in the present study.…”

Section: Studies On Steady/pulsatile Inflow Past Flexible Thin Structmentioning

confidence: 79%

The response of an elastic splitter plate attached to a cylinder to laminar pulsatile flow

Kundu

Soti

Bhardwaj

et al. 2017

Journal of Fluids and Structures

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The flow-induced deformation of a thin, elastic splitter plate attached to the rear of a circular cylinder and subjected to laminar pulsatile inflow is investigated. The cylinder and elastic splitter plate are contained within a narrow channel and the Reynolds number is mostly restricted to Re = 100, primarily covering the two-dimensional flow regime. An in-house fluidstructure interaction code is employed for simulations, which couples a sharp-interface immersed boundary method for the fluid dynamics with a finite-element method to treat the structural dynamics. The structural solver is implicitly (two-way) coupled with the flow solver using a partitioned approach. This implicit coupling ensures numerical stability at low structure-fluid density ratios. A power spectrum analysis of the time-varying plate displacement shows that the plate oscillates at more than a single frequency for pulsatile inflow, compared to a single frequency observed for steady inflow. The multiple frequencies obtained for the former case can be explained by beating between the applied and plate oscillatory signals. The plate attains a self-sustained time-periodic oscillation with a plateau amplitude in the case of steady flow, while the superimposition of pulsatile inflow with induced plate oscillation affects the plateau amplitude. Lock-in of the plate oscillation with the pulsatile inflow occurs at a forcing frequency that is twice of the plate natural frequency in a particular mode and this mode depends on the plate length. The plate displacement as well as pressure drag increases at the lock-in condition. The percentage change in the maximum plate 2 displacement, and skin-friction and pressure drag coefficients on the plate, due to pulsatile inflow is quantified. The non-linear dynamics of the plate and its coupling with the pulsatile flow are briefly discussed.

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Section: Studies On Steady/pulsatile Inflow Past Flexible Thin Structmentioning

confidence: 79%

The response of an elastic splitter plate attached to a cylinder to laminar pulsatile flow

Kundu

Soti

Bhardwaj

et al. 2017

Journal of Fluids and Structures

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“…These often make use of passive appendages attached to their bodies (plumed seeds, barbs, tails, and protrusions) to generate locomotion [7,8,9]. Recently, Lācis et al [7] demonstrated that the interaction between the wake of a falling bluff body and a protrusion clamped to its rear end can generate a sidewards drift by means of a symmetry-breaking instability similar to that of an inverted pendulum.…”

mentioning

confidence: 99%

Mass and Moment of Inertia Govern the Transition in the Dynamics and Wakes of Freely Rising and Falling Cylinders

et al. 2017

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In this Letter, we study the motion and wake-patterns of freely rising and falling cylinders in quiescent fluid. We show that the amplitude of oscillation and the overall system-dynamics are intricately linked to two parameters: the particle's mass-density relative to the fluid m * ≡ ρp/ρ f and its relative moment-of-inertia I * ≡ Ip/I f . This supersedes the current understanding that a critical mass density (m * ≈ 0.54) alone triggers the sudden onset of vigorous vibrations. Using over 144 combinations of m * and I * , we comprehensively map out the parameter space covering very heavy (m * > 10) to very buoyant (m * < 0.1) particles. The entire data collapses into two scaling regimes demarcated by a transitional Strouhal number, Stt ≈ 0.17. Stt separates a mass-dominated regime from a regime dominated by the particle's moment of inertia. A shift from one regime to the other also marks a gradual transition in the wake-shedding pattern: from the classical 2S (2-Single) vortex mode to a 2P (2-Pairs) vortex mode. Thus, auto-rotation can have a significant influence on the trajectories and wakes of freely rising isotropic bodies.Path-instabilities are a common observation in the dynamics of buoyant and heavy particles. Common examples are the fluttering of falling leaves and disks, and the cork-screw and spiral trajectories of air-bubbles rising in water [1,2,3]. The oscillatory dynamics of such particles can vary a lot depending on the particle's size, shape and its inertia, and the surrounding flow properties. This can be important in a variety of fields ranging from sediment transport and fluidization to multiphase particleand bubble-column reactors [4,5,6].Examples of organisms that exploit path-instabilities are plants and aquatic animals. These often make use of passive appendages attached to their bodies (plumed seeds, barbs, tails, and protrusions) to generate locomotion [7,8,9]. Recently, Lācis et al. [7] demonstrated that the interaction between the wake of a falling bluff body and a protrusion clamped to its rear end can generate a sidewards drift by means of a symmetry-breaking instability similar to that of an inverted pendulum. Such kinds of passive interactions are advantageous to locomotion, since no energy needs to be spent by the animal. Instead, the energy can be extracted through fluid-structure interaction.

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“…An example highlighting the non-trivial role of a passive appendage on the behavior of solid objects is discussed by Lacis et al (2014), where it is shown how the appendage interacts with the wake, thus changing the flow structure and, in turn, the system's dynamics. Using simple concepts, one could argue that adding a filament to the rear of the pendulum increases added mass effects, which, according to Eq.…”

Section: Control Of the Instabilitymentioning

confidence: 99%

“…Besides its applicability, the fluid-structure interaction poses fundamental problems. For example, recent studies have outlined a symmetry breaking mechanism that, so far, has eluded our intuitive understanding of how flows affect the shape and conformation of flexible objects (Bagheri et al, 2012;Lacis et al, 2014).…”

Section: Introductionmentioning

confidence: 98%

Galloping instability and control of a rigid pendulum in a flowing soap film

Orchini

Kellay

Mazzino

2015

Journal of Fluids and Structures

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A pendulum suspended in a fast flowing soap film may show sustained oscillations. The conditions necessary for self-excited motion to occur are outlined: a flow velocity above a threshold value along with geometrical constraints. The role of vortex shedding is discussed, and the observed instability is shown to be well-described by the galloping instability. Experimental results are supported by numerical simulations. Furthermore, we observe that the instability may be suppressed by attaching a long enough filament to the rear of the pendulu

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Passive appendages generate drift through symmetry breaking

Cited by 52 publications

References 26 publications

The response of an elastic splitter plate attached to a cylinder to laminar pulsatile flow

The response of an elastic splitter plate attached to a cylinder to laminar pulsatile flow

Mass and Moment of Inertia Govern the Transition in the Dynamics and Wakes of Freely Rising and Falling Cylinders

Galloping instability and control of a rigid pendulum in a flowing soap film

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