Clarifying the relationship between efficiency and resonance for flexible inertial swimmers

@article{Floryan2018ClarifyingTR,
  title={Clarifying the relationship between efficiency and resonance for flexible inertial swimmers},
  author={Daniel Floryan and Clarence W. Rowley},
  journal={Journal of Fluid Mechanics},
  year={2018},
  volume={853},
  pages={271 - 300}
}
We study a linear inviscid model of a passively flexible swimmer, calculating its propulsive performance, eigenvalues and eigenfunctions with an eye towards clarifying the relationship between efficiency and resonance. The frequencies of actuation and stiffness ratios we consider span a large range, while the mass ratio is mostly fixed to a low value representative of swimmers. We present results showing how the trailing edge deflection, thrust coefficient, power coefficient and efficiency vary… 

Distributed flexibility in inertial swimmers

TLDR
Results are presented showing how the trailing edge deflection, thrust coefficient, power coefficient and efficiency vary with frequency, mean stiffness and stiffness distribution, and speculate on the effects of a finite Reynolds number in the form of streamwise drag.

Analytical results for the propulsion performance of a flexible foil with prescribed pitching and heaving motions and passive small deflection

Abstract The propulsive performance of a flexible foil with prescribed pitching and heaving motions about any pivot point location and passive chordwise flexural deflection is analysed within the

Connections between resonance and nonlinearity in swimming performance of a flexible heaving plate

We investigate the role of resonance in finite-amplitude swimming of a flexible flat plate in a viscous fluid. The role of resonance in performance remains unclear for two reasons: (i) a lack of

A high-fidelity numerical study on the propulsive performance of pitching flexible plates

In this paper, we numerically investigate the propulsive performance of three-dimensional pitching flexible plates with varying flexibility and trailing edge shapes. We employ our recently developed

Material and geometric effects on propulsion of a fish tail

TLDR
Improvement in the thrust and propulsive efficiency over a specific range of non-dimensional flexibility defined by the ratio of the elastic forces to fluid pressure forces and Structural and flow characteristics associated with the improved performance are discussed.

Scaling the self-propulsive performance of pitching and heaving flexible plates

Abstract Self-propulsive performances of the flexible plates undergoing pitching and heaving motions are investigated numerically. The effects of multiple key dimensionless parameters are considered,

Optimal chordwise stiffness distribution for self-propelled heaving flexible plates

The effect of non-uniform chordwise stiffness distribution on the self-propulsive performance of three-dimensional flexible plates is studied numerically. Some typical stiffness distributions,

Hydromechanics and Optimization of Fast and Efficient Swimming

This dissertation focuses on the mechanics of locomotion through a fluid medium characterized by propulsors (fins and wings) with a large aspect ratio and a large Reynolds number. The subject so

References

SHOWING 1-10 OF 28 REFERENCES

Linear instability mechanisms leading to optimally efficient locomotion with flexible propulsors

We present the linear stability analysis of experimental measurements obtained from unsteady flexible pitching panels. The analysis establishes the connections among the wake dynamics, propulsor

Optimal flexibility of a flapping appendage in an inviscid fluid

  • S. Alben
  • Physics
    Journal of Fluid Mechanics
  • 2008
We present a new formulation of the motion of a flexible body with a vortex-sheet wake and use it to study propulsive forces generated by a flexible body pitched periodically at the leading edge in

Scaling the propulsive performance of heaving flexible panels

Abstract We present an experimental investigation of flexible panels actuated with heave oscillations at their leading edge. Results are presented from kinematic video analysis, particle image

Thrust generation by a heaving flexible foil: Resonance, nonlinearities, and optimality

Flexibility of marine animal fins has been thought to enhance swimming performance. However, despite numerous experimental and numerical studies on flapping flexible foils, there is still no clear

Resonance and propulsion performance of a heaving flexible wing

The influence of the bending rigidity of a flexible heaving wing on its propulsive performance in a two-dimensional imposed parallel flow is investigated in the inviscid limit. Potential flow theory

Rather than resonance, flapping wing flyers may play on aerodynamics to improve performance

TLDR
It is shown that flapping flyers optimize their performance not by especially looking for resonance to achieve larger flapping amplitudes with less effort, but by tuning the temporal evolution of the wing shape to optimize the aerodynamics.

Effects of flexibility on the aerodynamic performance of flapping wings

TLDR
It seems that the maximum propulsive force is obtained when flapped near the resonance, whereas the optimal propulsive efficiency is reached when flapping at about half of the natural frequency; both are supported by the reported studies.

Maximizing the efficiency of a flexible propulsor using experimental optimization

TLDR
Experimental gradient-based optimization is used to maximize the propulsive efficiency of a heaving and pitching flexible panel and the multi-dimensionality and multi-modality of the efficiency response demonstrate that experimental optimization is well-suited for the design of flexible underwater propulsors.

Influence of flexibility on the aerodynamic performance of a hovering wing

TLDR
It was found that flexibility can enhance aerodynamic performance and that the best performance is realized when the wing is excited by a non-linear resonance at 1/3 of the natural frequency, which points to the importance of considering non- linear resonances for enhancing aerodynamics performance.

Analytical results on the role of flexibility in flapping propulsion

  • M. Moore
  • Physics
    Journal of Fluid Mechanics
  • 2014
Abstract Wing or fin flexibility can dramatically affect the performance of flying and swimming animals. Both laboratory experiments and numerical simulations have been used to study these effects,