Computational modelling and analysis of the hydrodynamics of a highly deformable fish pectoral fin

2010 ◽  
Vol 645 ◽  
pp. 345-373 ◽  
Author(s):  
H. DONG ◽  
M. BOZKURTTAS ◽  
R. MITTAL ◽  
P. MADDEN ◽  
G. V. LAUDER
Keyword(s):  
Vortex Dynamics ◽  
Lepomis Macrochirus ◽  
Three Dimensional ◽  
Computational Modelling ◽  
Force Production ◽  
Tip Vortex ◽  
Pectoral Fin ◽  
Surface Distribution ◽  
Propulsive Performance ◽  
Thrust Production

Numerical simulations are used to investigate the flow associated with a bluegill sunfish (Lepomis macrochirus) pectoral fin during steady forward motion. The simulations are intended to match the experiments of Lauder et al. (Bioinsp. Biomim., vol. 1, 2006, p. S25), and the results obtained from the simulations complement the experimental analysis. The focus of the current paper is on the quantitative characterization of the propulsive performance of the pectoral fin, which undergoes significant deformation during its stroke. This includes a detailed analysis of the thrust production mechanisms as well as their connection to the vortex dynamics and other flow features. The simulations indicate that the fish fin produces high propulsive performance by employing a complex fin gait driven by active and passive fin deformation. By connecting the vortex dynamics and fin kinematics with the surface distribution of the force on the fin, it is found that during abduction, the fin moves such that the tip of the fin undergoes a complex, three-dimensional flapping motion that produces a strong and long-lasting, attached tip vortex. This tip vortex is associated with most of the thrust production during the abduction phase of the stroke. During the adduction phase, the fin motion is similar to a ‘paddling’ stroke. Comparisons are made with rigid flapping foils to provide insights into the remarkable performance of the fish fin and to interpret the force production from the viewpoint of functional morphology.

Fluid dynamics of flapping aquatic flight in the bird wrasse:three-dimensional unsteady computations with fin deformation

2002 ◽  
Vol 205 (19) ◽  
pp. 2997-3008 ◽  
Author(s):  
Ravi Ramamurti ◽  
William C. Sandberg ◽  
Rainald Löhner ◽  
Jeffrey A. Walker ◽  
Mark W. Westneat
Keyword(s):  
Fluid Dynamics ◽  
Steady State ◽  
Three Dimensional ◽  
Force Production ◽  
Time History ◽  
The Body ◽  
Vertical Acceleration ◽  
Field Variation ◽  
Pectoral Fin ◽  
Pectoral Fins

SUMMARY Many fishes that swim with the paired pectoral fins use fin-stroke parameters that produce thrust force from lift in a mechanism of underwater flight. These locomotor mechanisms are of interest to behavioral biologists,biomechanics researchers and engineers. In the present study, we performed the first three-dimensional unsteady computations of fish swimming with oscillating and deforming fins. The objective of these computations was to investigate the fluid dynamics of force production associated with the flapping aquatic flight of the bird wrasse Gomphosus varius. For this computational work, we used the geometry of the wrasse and its pectoral fin,and previously measured fin kinematics, as the starting points for computational investigation of three-dimensional (3-D) unsteady fluid dynamics. We performed a 3-D steady computation and a complete set of 3-D quasisteady computations for a range of pectoral fin positions and surface velocities. An unstructured, grid-based, unsteady Navier—Stokes solver with automatic adaptive remeshing was then used to compute the unsteady flow about the wrasse through several complete cycles of pectoral fin oscillation. The shape deformation of the pectoral fin throughout the oscillation was taken from the experimental kinematics. The pressure distribution on the body of the bird wrasse and its pectoral fins was computed and integrated to give body and fin forces which were decomposed into lift and thrust. The velocity field variation on the surface of the wrasse body, on the pectoral fins and in the near-wake was computed throughout the swimming cycle. We compared our computational results for the steady, quasi-steady and unsteady cases with the experimental data on axial and vertical acceleration obtained from the pectoral fin kinematics experiments. These comparisons show that steady state computations are incapable of describing the fluid dynamics of flapping fins. Quasi-steady state computations, with correct incorporation of the experimental kinematics, are useful when determining trends in force production, but do not provide accurate estimates of the magnitudes of the forces produced. By contrast, unsteady computations about the deforming pectoral fins using experimentally measured fin kinematics were found to give excellent agreement, both in the time history of force production throughout the flapping strokes and in the magnitudes of the generated forces.

scholarly journals On the persistence of memory: do initial conditions impact vortex formation?

2013 ◽  
Vol 736 ◽  
pp. 91-106 ◽  
Author(s):  
Jochen Kriegseis ◽  
Matthias Kinzel ◽  
David E. Rival
Keyword(s):  
Particle Tracking Velocimetry ◽  
Initial Conditions ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Force Production ◽  
Initial Boundary ◽  
Tip Vortex ◽  
Stream Velocity ◽  
Force Measurements ◽  
Effective Velocity

AbstractAn investigation into redistribution of vorticity for rapidly accelerating plates with varying kinematics and initial conditions has been performed. Both three-dimensional particle tracking velocimetry and direct force measurements were applied simultaneously. The effective velocity of the feeding shear layer has been identified as the appropriate characteristic velocity rather than the commonly used plunge or free stream velocity. Based on this new normalization for circulation, it has been demonstrated that the existence of initial boundary-layer vorticity on the plunging plate – at least in the near-midplane region – does not contribute to the eventual vortex formation process. In accordance with the literature, however, the tip vortex positioning relative to the plate surface has been identified as an important contributor in the overall force production, particularly once the plate acceleration has ceased.

scholarly journals Scaling laws for the propulsive performance of three-dimensional pitching propulsors

2019 ◽  
Vol 871 ◽  
pp. 1117-1138 ◽  
Author(s):  
Fatma Ayancik ◽  
Qiang Zhong ◽  
Daniel B. Quinn ◽  
Aaron Brandes ◽  
Hilary Bart-Smith ◽  
...  
Keyword(s):  
Scaling Laws ◽  
Three Dimensional ◽  
Added Mass ◽  
Scaling Relations ◽  
The Novel ◽  
Vortex System ◽  
Propulsive Performance ◽  
Dimensional Scaling ◽  
Aspect Ratios ◽  
Thrust Production

Scaling laws for the thrust production and energetics of self-propelled or fixed-velocity three-dimensional rigid propulsors undergoing pitching motions are presented. The scaling relations extend the two-dimensional scaling laws presented in Moored & Quinn (AIAA J., 2018, pp. 1–15) by accounting for the added mass of a finite-span propulsor, the downwash/upwash effects from the trailing vortex system of a propulsor and the elliptical topology of shedding trailing-edge vortices. The novel three-dimensional scaling laws are validated with self-propelled inviscid simulations and fixed-velocity experiments over a range of reduced frequencies, Strouhal numbers and aspect ratios relevant to bio-inspired propulsion. The scaling laws elucidate the dominant flow physics behind the thrust production and energetics of pitching bio-propulsors, and they provide guidance for the design of bio-inspired propulsive systems.

Research on the Hydrodynamics of a Horizontal Trigonal Pectoral Fin Propulsor Actuated by SMA Wires

2010 ◽  
Vol 44-47 ◽  
pp. 2548-2552
Author(s):  
Zhen Long Wang ◽  
Jian Li ◽  
Yang Wei Wang ◽  
Yu Kui Wang
Keyword(s):  
Thrust Force ◽  
Force Measurement ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Force Production ◽  
Pectoral Fin ◽  
Set Up ◽  
Batoid Fishes ◽  
Manta Ray ◽  
Surrounding Fluid

Inspired by some batoid fishes using horizontal trigonal pectoral fin for propulsion or maneuverability, a micro flexible mimetic propulsor actuated by shape memory alloy (SMA) wires is presented. Firstly, based on the motion characters of the pectoral fin of manta ray, a simplified kinematics model was set up. Secondly, a three-dimensional numerical simulation on the oscillatory fin was performed by computational fluid dynamic (CFD) to investigate the interaction with the surrounding fluid and the propulsive force production. Thirdly, action experiment of the propulsor is done to verify the concept. At last, the propulsive performance of the propulsor is evaluated through thrust force measurement experiments. The experimental results accord with the CFD results well. The propulsor have potential feasibility applying in automatic underwater vehicles (AUV).

3D Profile Variety Measurement of Pectoral Fin in Fish Fast Start

2011 ◽  
Vol 83 ◽  
pp. 280-284
Author(s):  
Ming Jiang ◽  
Shu Zhang ◽  
Xiao Yuan He
Keyword(s):  
Fourier Transform ◽  
High Speed ◽  
Kinetic Characteristic ◽  
Three Dimensional ◽  
Pectoral Fin ◽  
Fourier Transform Profilometry ◽  
Fast Start ◽  
Fringe Patterns ◽  
3D Information ◽  
3D Profile

Fast-starts are brief, sudden accelerations used by fish during predator-prey encounters. In this paper, a three-dimensional (3D) test and analysis method is critical to understand the function of the pectoral fin during maneuvers. An experiment method based on Fourier Transform Profilometry for 3D pectoral fin profile variety during fish maneuvers is proposed. This method was used in a carp fast-start during prey. Projecting the moiré fringes onto a carp pectoral fin it will produce the deformed fringe patterns contain 3D information. A high speed camera captures these time-sequence images. By Fourier transform, filter, inverse Fourier transform and unwrap these phase maps in 3D phase space, the complex pectoral fin profile variety were really reconstructed. The present study provides a new method to quantify the analysis of kinetic characteristic of the pectoral fin during maneuvers.

scholarly journals Comparative investigations in the effect of angle of attack profile on hydrodynamic performance of bio-inspired foil, (corrected)

2013 ◽  
Vol 10 (2) ◽  
pp. 99-108 ◽  
Author(s):  
J. A. Esfahani ◽  
E. Barati ◽  
Hamid Reza Karbasian
Keyword(s):  
Angle Of Attack ◽  
Underwater Vehicles ◽  
Hydrodynamic Performance ◽  
Profile Function ◽  
Flapping Foil ◽  
Propulsive Performance ◽  
Wide Range ◽  
Effective Angle ◽  
Thrust Production ◽  
Optimum Profile

In flapping underwater vehicles the propulsive performance of harmonically sinusoidal heaving and pitching foil will be degraded by some awkward changes in effective angle of attack profile, as the Strouhal number increases. This paper surveys different angle of attack profiles (Sinusoidal, Square, Sawtooth and Cosine) and considers their thrust production ability. In the wide range of Strouhal numbers, thrust production of Square profile is considerable but it has a discontinuity in heave velocity profile, in which an infinite acceleration exists. This problem poses a significant defect in control of flapping foil. A novel profile function is proposed to omit sharp changes in heave velocity and acceleration. Furthermore, an optimum profile is found for different Strouhal numbers with respect to Square angle of attack profile.DOI: http://dx.doi.org/10.3329/jname.v10i2.14229

Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics Model

1999 ◽  
Vol 121 (1) ◽  
pp. 198-204 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Vortex Core ◽  
Bubble Dynamics ◽  
Three Dimensional ◽  
Window Size ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Cavitation Inception ◽  
Flow Effects ◽  
Bubble Sizes ◽  
Real Flow

The Rayleigh-Plesset bubble dynamics equation coupled with the bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the bubble was passively convected. A “window of opportunity” through which a candidate bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial bubble sizes. It was found that bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.

Functional implications of supercontracting muscle in the chameleon tongue retractors

2001 ◽  
Vol 204 (21) ◽  
pp. 3621-3627 ◽  
Author(s):  
Anthony Herrel ◽  
Jay J. Meyers ◽  
Peter Aerts ◽  
Kiisa C. Nishikawa
Keyword(s):  
Prey Capture ◽  
Three Dimensional ◽  
Force Production ◽  
Retractor Muscle ◽  
Muscle Physiology ◽  
Large Prey ◽  
Wide Range ◽  
Ambush Predators ◽  
Full Body

SUMMARYChameleons capture prey items using a ballistic tongue projection mechanism that is unique among lizards. During prey capture, the tongue can be projected up to two full body lengths and may extend up to 600 % of its resting length. Being ambush predators, chameleons eat infrequently and take relatively large prey. The extreme tongue elongation (sixfold) and the need to be able to retract fairly heavy prey at any given distance from the mouth are likely to place constraints on the tongue retractor muscles. The data examined here show that in vivo retractor force production is almost constant for a wide range of projection distances. An examination of muscle physiology and of the ultrastructure of the tongue retractor muscle shows that this is the result (i) of active hyoid retraction, (ii) of large muscle filament overlap at maximal tongue extension and (iii) of the supercontractile properties of the tongue retractor muscles. We suggest that the chameleon tongue retractor muscles may have evolved supercontractile properties to enable a substantial force to be produced over a wide range of tongue projection distances. This enables chameleons successfully to retract even large prey from a variety of distances in their complex three-dimensional habitat.

Computational Investigation of Thrust Production of a Dolphin at Various Swimming Speeds

2021 ◽  
Author(s):  
Junshi Wang ◽  
Vadim Pavlov ◽  
Zhipeng Lou ◽  
Haibo Dong
Keyword(s):  
Surface Pressure ◽  
Swimming Performance ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Immersed Boundary ◽  
Reconstruction Method ◽  
Force Coefficient ◽  
Speed Increase ◽  
Generation Mechanisms ◽  
Thrust Production

Abstract Dolphins are known for their outstanding swimming performance. However, the difference in flow physics at different speeds remains elusive. In this work, the underlying mechanisms of dolphin swimming at three speeds, 2 m/s, 5 m/s, and 8 m/s, are explored using a combined experimental and numerical approach. Using the scanned CAD model of the Atlantic white-sided dolphin (Lagenorhynchus acutus) and virtual skeleton-based surface reconstruction method, a three-dimensional high-fidelity computational model is obtained with time-varying kinematics. A sharp-interface immersed-boundary-method (IBM) based direct numerical simulation (DNS) solver is employed to calculate the corresponding thrust production, wake structure, and surface pressure at different swimming speeds. It is found that the fluke keeps its effective angle of attack at high values for about 60% of each stroke. The total pressure force coefficient along the x-axis converges as the speed increase. The flow and surface pressure analysis both show considerable differences between lower (2 m/s) and higher (5 m/s and 8 m/s) speeds. The results from this work help to bring new insight into understanding the force generation mechanisms of the highly efficient dolphin swimming and offer potential suggestions to the future designs of unmanned underwater vehicles.

scholarly journals Variable Thumb Moment Arm Modeling and Thumb-Tip Force Production of a Human-Like Robotic Hand

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Taylor D. Niehues ◽  
Ashish D. Deshpande
Keyword(s):  
Physical Simulation ◽  
Three Dimensional ◽  
Force Production ◽  
Human Hand ◽  
Robotic Hand ◽  
Motion Data ◽  
Moment Arms ◽  
Musculoskeletal Structure ◽  
Thumb Motion ◽  
Force Vectors

The anatomically correct testbed (ACT) hand mechanically simulates the musculoskeletal structure of the fingers and thumb of the human hand. In this work, we analyze the muscle moment arms (MAs) and thumb-tip force vectors in the ACT thumb in order to compare the ACT thumb's mechanical structure to the human thumb. Motion data are used to determine joint angle-dependent MA models, and thumb-tip three-dimensional (3D) force vectors are experimentally analyzed when forces are applied to individual muscles. Results are presented for both a nominal ACT thumb model designed to match human MAs and an adjusted model that more closely replicates human-like thumb-tip forces. The results confirm that the ACT thumb is capable of faithfully representing human musculoskeletal structure and muscle functionality. Using the ACT hand as a physical simulation platform allows us to gain a better understanding of the underlying biomechanical and neuromuscular properties of the human hand to ultimately inform the design and control of robotic and prosthetic hands.

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