A hydrodynamic analysis of fish swimming speed: wake structure and locomotor force in slow and fast labriform swimmers

2000 ◽  
Vol 203 (16) ◽  
pp. 2379-2393 ◽  
Author(s):  
E.G. Drucker ◽  
G.V. Lauder
Keyword(s):  
Vortex Ring ◽  
Swimming Speed ◽  
Lepomis Macrochirus ◽  
Vortex Rings ◽  
Bluegill Sunfish ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
Lateral Forces ◽  
Low Speeds ◽  
All Speeds

Past study of interspecific variation in the swimming speed of fishes has focused on internal physiological mechanisms that may limit the ability of locomotor muscle to generate power. In this paper, we approach the question of why some fishes are able to swim faster than others from a hydrodynamic perspective, using the technique of digital particle image velocimetry which allows measurement of fluid velocity and estimation of wake momentum and mechanical forces for locomotion. We investigate the structure and strength of the wake in three dimensions to determine how hydrodynamic force varies in two species that differ markedly in maximum swimming speed. Black surfperch (Embiotoca jacksoni) and bluegill sunfish (Lepomis macrochirus) swim at low speeds using their pectoral fins exclusively, and at higher speeds switch to combined pectoral and caudal fin locomotion. E. jacksoni can swim twice as fast as similarly sized L. macrochirus using the pectoral fins alone. The pectoral fin wake of black surfperch at all speeds consists of two distinct vortex rings linked ventrally. As speed increases from 1.0 to 3.0 L s(−)(1), where L is total body length, the vortex ring formed on the fin downstroke reorients to direct force increasingly downstream, parallel to the direction of locomotion. The ratio of laterally to downstream-directed force declines from 0.93 to 0.07 as speed increases. In contrast, the sunfish pectoral fin generates a single vortex ring per fin beat at low swimming speeds and a pair of linked vortex rings (with one ring only partially complete and attached to the body) at maximal labriform speeds. Across a biologically relevant range of swimming speeds, bluegill sunfish generate relatively large lateral forces with the paired fins: the ratio of lateral to downstream force remains at or above 1.0 at all speeds. By increasing wake momentum and by orienting this momentum in a direction more favorable for thrust than for lateral force, black surfperch are able to swim at twice the speed of bluegill sunfish using the pectoral fins. In sunfish, without a reorientation of shed vortices, increases in power output of pectoral fin muscle would have little effect on maximum locomotor speed. We present two hypotheses relating locomotor stability, maneuverability and the structure of the vortex wake. First, at low speeds, the large lateral forces exhibited by both species may be necessary for stability. Second, we propose a potential hydrodynamic trade-off between speed and maneuverability that arises as a geometric consequence of the orientation of vortex rings shed by the pectoral fins. Bluegill sunfish may be more maneuverable because of their ability to generate large mediolateral force asymmetries between the left- and right-side fins.

KINEMATICS OF PECTORAL FIN LOCOMOTION IN THE BLUEGILL SUNFISH LEPOMIS MACROCHIRUS

1994 ◽  
Vol 189 (1) ◽  
pp. 133-161 ◽  
Author(s):  
A Gibb ◽  
B Jayne ◽  
G Lauder
Keyword(s):  
Swimming Speed ◽  
Beat Frequency ◽  
Lepomis Macrochirus ◽  
Force Balance ◽  
Total Force ◽  
Bluegill Sunfish ◽  
Pectoral Fin ◽  
Lateral Projection ◽  
Pectoral Fins ◽  
Distal Edge

The pectoral fins of ray-finned fishes are flexible and capable of complex movements, and yet little is known about the pattern of fin deformation during locomotion. For the most part, pectoral fins have been modeled as rigid plates. In order to examine the movements of different portions of pectoral fins, we quantified the kinematics of pectoral fin locomotion in the bluegill sunfish Lepomis macrochirus using several points on the distal fin edge and examined the effects of swimming speed on fin movements. We simultaneously videotaped the ventral and lateral views of pectoral fins of four fish swimming in a flow tank at five speeds ranging from 0.3 to 1.1 total lengths s-1. Four markers, placed on the distal edge of the fin, facilitated field-by-field analysis of kinematics. We used analyses of variance to test for significant variation with speed and among the different marker positions. Fin beat frequency increased significantly from 1.2 to 2.1 Hz as swimming speed increased from 0.3 to 1.0 total lengths s-1. Maximal velocities of movement for the tip of the fin during abduction and adduction generally increased significantly with increased swimming speed. The ratio of maximal speed of fin retraction to swimming speed declined steadily from 2.75 to 1.00 as swimming speed increased. Rather than the entire distal edge of the fin always moving synchronously, markers had phase lags as large as 32 with respect to the dorsal edge of the fin. The more ventral and proximal portions of the fin edge usually had smaller amplitudes of movement than did the more dorsal and distal locations. With increased swimming speed, the amplitudes of the lateral and longitudinal fin movements generally decreased. We used two distal markers and one basal reference point to determine the orientation of various planar fin elements. During early adduction and most of abduction, these planar fin elements usually had positive angles of attack. Because of fin rotation, angles of attack calculated from three-dimensional data differed considerably from those estimated from a simple lateral projection. As swimming speed increased, the angles of attack of the planar fin elements with respect to the overall direction of swimming approached zero. The oscillatory movements of the pectoral fins of bluegill suggest that both lift- and drag-based propulsive mechanisms are used to generate forward thrust. In addition, the reduced frequency parameter calculated for the pectoral fin of Lepomis (sigma=0.85) and the Reynolds number of 5x10(3) indicate that acceleration reaction forces may contribute significantly to thrust production and to the total force balance on the fin.

Understanding the Hydrodynamics of Swimming: From Fish Fins to Flexible Propulsors for Autonomous Underwater Vehicles

2008 ◽  
Vol 58 ◽  
pp. 193-202 ◽  
Author(s):  
Meliha Bozkurttas ◽  
James Tangorra ◽  
George Lauder ◽  
Rajat Mittal
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Mechanical Design ◽  
Research Effort ◽  
Autonomous Underwater Vehicles ◽  
Lepomis Macrochirus ◽  
Direct Result ◽  
Bluegill Sunfish ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
Vectored Thrust

The research effort described here is concerned with developing a maneuvering propulsor for an autonomous underwater vehicle (AUV’s) based on the mechanical design and performance of sunfish pectoral fin. Bluegill sunfish (Lepomis macrochirus) are highly maneuverable bony fishes that have been the subject of a number of experimental analyses of locomotor function [5, 6]. Although swimming generally involves the coordinated movement of many fin surfaces, the sunfish is capable of propulsion and maneuvering using almost exclusively the pectoral fins. They use pectoral fins exclusively for propulsion at speeds of less than 1.1 body length per second (BL/s). The curve in Fig. 1 depicts two peaks of body acceleration of bluegill sunfish during steady forward swimming. These abilities are the direct result of their pectoral fins being highly deformable control surfaces that can create vectored thrust. The motivation here is that by understanding these complex, highly controlled movements and by borrowing appropriately from pectoral fin design, a bio-robotic propulsor can be designed to provide vectored thrust and high levels of control to AUVs. This paper will focus on analyses of bluegill sunfish’s pectoral fin hydrodynamics which were carried out to guide the design of a flexible propulsor for AUV’s

Wake dynamics and fluid forces of turning maneuvers in sunfish

2001 ◽  
Vol 204 (3) ◽  
pp. 431-442 ◽  
Author(s):  
E. Drucker ◽  
G. Lauder
Keyword(s):  
Vortex Ring ◽  
Thrust Force ◽  
Lepomis Macrochirus ◽  
Lateral Force ◽  
The Body ◽  
Pectoral Fin ◽  
Fluid Forces ◽  
Pectoral Fins ◽  
Wide Range ◽  
Weak Side

While experimental analyses of steady rectilinear locomotion in fishes are common, unsteady movement involving time-dependent variation in heading, speed and acceleration probably accounts for the greatest portion of the locomotor time budget. Turning maneuvers, in particular, are key elements of the unsteady locomotor repertoire of fishes and, by many species, are accomplished by generating asymmetrical forces with the pectoral fins. The development of such left-right asymmetries in force production is a critical and as yet unstudied aspect of aquatic locomotor dynamics. In this paper, we measure the fluid forces exerted by the left and right pectoral fins of bluegill sunfish (Lepomis macrochirus) during turning using digital particle image velocimetry (DPIV). DPIV allowed quantification of water velocity fields, and hence momentum, in the wake of the pectoral fins as sunfish executed turns; forces exerted during turning were compared with those generated by the immediately preceding fin beats during steady swimming. Sunfish generate the forces required for turning by modulating two variables: wake momentum and pectoral fin stroke timing. Fins on opposite sides of the fish play functionally distinct roles during turning maneuvers. The fin nearer the stimulus inducing the turn (i.e. the strong side fin) generates a laterally oriented vortex ring with a strong central jet whose associated lateral force is four times greater than that produced during steady swimming. Little posterior (thrust) force is generated by the strong-side fin, and this fin therefore acts to rotate the body away from the source of the stimulus. The contralateral (weak-side) fin generates a posteriorly oriented vortex ring with a thrust force nine times that produced by the fin during steady swimming. Minimal lateral force is exerted by the weak-side fin, and this fin therefore acts primarily to translate the body linearly away from the stimulus. Turning with the paired fins is not simply steady swimming performed unilaterally. Instead, turning involves asymmetrical fin movements and fluid forces that are distinct in both direction and magnitude from those used to swim forward at constant speed. These data reflect the plasticity of the teleost pectoral fin in performing a wide range of steady and unsteady locomotor tasks.

Thrust Production in Highly Flexible Pectoral Fins: A Computational Dissection

2011 ◽  
Vol 45 (4) ◽  
pp. 56-64 ◽  
Author(s):  
Srinivas Ramakrishnan ◽  
Meliha Bozkurttas ◽  
Rajat Mittal ◽  
George V. Lauder
Keyword(s):  
Computational Analysis ◽  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Bluegill Sunfish ◽  
Robust Performance ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
And Performance ◽  
Thrust Production ◽  
Computational Dissection

AbstractBluegill sunfish pectoral fins represent a remarkable success in evolutionary terms as a means of propulsion in challenging environments. Attempts to mimic their design in the context of autonomous underwater vehicles have overwhelmingly relied on the analysis of steady swimming. Experimental observations of maneuvers reveal that the kinematics of fin and wake dynamics exhibit characteristics that are distinctly different from steady swimming. We present a computational analysis that compares, qualitatively and quantitatively, the wake hydrodynamics and performance of the bluegill sunfish pectoral fin for two modes of swimming: steady swimming and a yaw turn maneuver. It is in this context that we comment on the role that flexibility plays in the success of the pectoral fin as a versatile propulsor. Specifically, we assess the performance of the fin by conducting a “virtual dissection” where only a portion of fin is retained. Approximately 90% of peak thrust for steady swimming is recovered using only the dorsal half. This figure drops to 70% for the yaw turn maneuver. Our findings suggest that designs based on fin analysis that account for various locomotion modes can lead to more robust performance than those based solely on steady swimming.

Effect of Morphological Fin-Curl on the Swimming Performance and Station-Holding Ability of Juvenile Shovelnose Sturgeon

2016 ◽  
Vol 7 (1) ◽  
pp. 198-204 ◽  
Author(s):  
David Deslauriers ◽  
Ryan Johnston ◽  
Steven R. Chipps
Keyword(s):  
Swimming Speed ◽  
Early Onset ◽  
Positive Relationship ◽  
Swimming Performance ◽  
Fork Length ◽  
Critical Swimming Speed ◽  
Pectoral Fin ◽  
Speed Test ◽  
Shovelnose Sturgeon ◽  
Pectoral Fins

Abstract We assessed the effect of fin-curl on the swimming and station-holding ability of juvenile shovelnose sturgeon Scaphirhynchus platorynchus (mean fork length = 17 cm; mean weight = 16 g; n = 21) using a critical swimming speed test performed in a small swim chamber (90 L) at 20°C. We quantified fin-curl severity using the pectoral fin index. Results showed a positive relationship between pectoral fin index and critical swimming speed indicative of reduced swimming performance displayed by fish afflicted with a pectoral fin index < 8%. Fin-curl severity, however, did not affect the station-holding ability of individual fish. Rather, fish affected with severe fin-curl were likely unable to use their pectoral fins to position their body adequately in the water column, which led to the early onset of fatigue. Results generated from this study should serve as an important consideration for future stocking practices.

scholarly journals Hydrodynamics of linear acceleration in bluegill sunfish Lepomis macrochirus

2018 ◽  
Author(s):  
Tyler N. Wise ◽  
Margot A. B. Schwalbe ◽  
Eric D. Tytell
Keyword(s):  
Swimming Speed ◽  
High Speed ◽  
Fluid Dynamic ◽  
Natural Habitat ◽  
Lepomis Macrochirus ◽  
Linear Acceleration ◽  
High Amplitude ◽  
The Body ◽  
Bluegill Sunfish ◽  
Tail Beat

SUMMARY STATEMENTBluegill sunfish accelerate primarily by increasing the total amount of force produced in each tail beat but not by substantially redirecting forces.ABSTRACTIn their natural habitat, fish rarely swim steadily. Instead they frequently accelerate and decelerate. Relatively little is known about how fish produce extra force for acceleration in routine swimming behavior. In this study, we examined the flow around bluegill sunfish Lepomis macrochirus during steady swimming and during forward acceleration, starting at a range of initial swimming speeds. We found that bluegill produce vortices with higher circulation during acceleration, indicating a higher force per tail beat, but do not substantially redirect the force. We quantified the flow patterns using high speed video and particle image velocimetry and measured acceleration with small inertial measurement units attached to each fish. Even in steady tail beats, the fish accelerates slightly during each tail beat, and the magnitude of the acceleration varies. In steady tail beats, however, a high acceleration is followed by a lower acceleration or a deceleration, so that the swimming speed is maintained; in unsteady tail beats, the fish maintains the acceleration over several tailbeats, so that the swimming speed increases. We can thus compare the wake and kinematics during single steady and unsteady tailbeats that have the same peak acceleration. During unsteady tailbeats when the fish accelerates forward for several tailbeats, the wake vortex forces are much higher than those at the same acceleration during single tailbeats in steady swimming. The fish also undulates its body at higher amplitude and frequency during unsteady tailbeats. These kinematic changes likely increase the fluid dynamic added mass of the body, increasing the forces required to sustain acceleration over several tailbeats. The high amplitude and high frequency movements are also likely required to generate the higher forces needed for acceleration. Thus, it appears that bluegill sunfish face a tradeoff during acceleration: the body movements required for acceleration also make it harder to accelerate.

Pectoral fin locomotion in batoid fishes: undulation versus oscillation

2001 ◽  
Vol 204 (2) ◽  
pp. 379-394 ◽  
Author(s):  
L.J. Rosenberger
Keyword(s):  
Swimming Speed ◽  
Beat Frequency ◽  
Wave Number ◽  
Phylogenetic Position ◽  
Swimming Velocity ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
Rhinoptera Bonasus ◽  
Raja Eglanteria ◽  
Fin Length

This study explores the dichotomy between undulatory (passing multiple waves down the fin or body) and oscillatory (flapping) locomotion by comparing the kinematics of pectoral fin locomotion in eight species of batoids (Dasyatis americana, D. sabina, D. say, D. violacea, Gymnura micrura, Raja eglanteria, Rhinobatos lentiginosus and Rhinoptera bonasus) that differ in their swimming behavior, phylogenetic position and lifestyle. The goals of this study are to describe and compare the pectoral fin locomotor behavior of the eight batoid species, to clarify how fin movements change with swimming speed for each species and to analyze critically the undulation/oscillation continuum proposed by Breder using batoids as an example. Kinematic data were recorded for each species over a range of swimming velocities (1–3 disc lengths s(−1)). The eight species in this study vary greatly in their swimming modes. Rhinobatos lentiginosus uses a combination of axial-based and pectoral-fin-based undulation to move forward through the water, with primary thrust generated by the tail. The pectoral fins are activated in short undulatory bursts for increasing swimming speed and for maneuvering. Raja eglanteria uses a combination of pectoral and pelvic locomotion, although only pectoral locomotion is analyzed here. The other six species use pectoral locomotion exclusively to propel themselves through the water. Dasyatis sabina and D. say have the most undulatory fins with an average of 1.3 waves per fin length, whereas Rhinoptera bonasus has the most oscillatory fin behavior with 0.4 waves per fin length. The remaining species range between these two extremes in the degree of undulation present on their fins. There is an apparent trade-off between fin-beat frequency and amplitude. Rhinoptera bonasus has the lowest frequency and the highest fin amplitude, whereas Rhinobatos lentiginosus has the highest frequency and the lowest amplitude among the eight species examined. The kinematic variables that batoids modify to change swimming velocity vary among different species. Rhinobatos lentiginosus increases its tail-beat frequency to increase swimming speed. In contrast, the four Dasyatis species increase swimming speed by increasing frequency and wavespeed, although D. americana also changes wave number. Raja eglanteria modifies its swimming velocity by changing wavespeed and wave number. Rhinoptera bonasus increases wavespeed, Gymnura micrura decreases wave number, and both Rhinoptera bonasus and Gymnura micrura increase fin-tip velocity to increase swimming velocity. Batoid species fall onto a continuum between undulation and oscillation on the basis of the number of waves present on the fins.

Locomotor forces on a swimming fish: three-dimensional vortex wake dynamics quantified using digital particle image velocimetry

1999 ◽  
Vol 202 (18) ◽  
pp. 2393-2412 ◽  
Author(s):  
E.G. Drucker ◽  
G.V. Lauder
Keyword(s):  
Particle Image Velocimetry ◽  
Swimming Speed ◽  
Particle Image ◽  
Fluid Velocity ◽  
Lepomis Macrochirus ◽  
Three Dimensional ◽  
Digital Particle Image Velocimetry ◽  
Force Balance ◽  
Vortex Rings ◽  
Image Velocimetry

Quantifying the locomotor forces experienced by swimming fishes represents a significant challenge because direct measurements of force applied to the aquatic medium are not feasible. However, using the technique of digital particle image velocimetry (DPIV), it is possible to quantify the effect of fish fins on water movement and hence to estimate momentum transfer from the animal to the fluid. We used DPIV to visualize water flow in the wake of the pectoral fins of bluegill sunfish (Lepomis macrochirus) swimming at speeds of 0.5-1.5 L s(−)(1), where L is total body length. Velocity fields quantified in three perpendicular planes in the wake of the fins allowed three-dimensional reconstruction of downstream vortex structures. At low swimming speed (0.5 L s(−)(1)), vorticity is shed by each fin during the downstroke and stroke reversal to generate discrete, roughly symmetrical, vortex rings of near-uniform circulation with a central jet of high-velocity flow. At and above the maximum sustainable labriform swimming speed of 1.0 L s(−)(1), additional vorticity appears on the upstroke, indicating the production of linked pairs of rings by each fin. Fluid velocity measured in the vicinity of the fin indicates that substantial spanwise flow during the downstroke may occur as vortex rings are formed. The forces exerted by the fins on the water in three dimensions were calculated from vortex ring orientation and momentum. Mean wake-derived thrust (11.1 mN) and lift (3.2 mN) forces produced by both fins per stride at 0.5 L s(−)(1) were found to match closely empirically determined counter-forces of body drag and weight. Medially directed reaction forces were unexpectedly large, averaging 125 % of the thrust force for each fin. Such large inward forces and a deep body that isolates left- and right-side vortex rings are predicted to aid maneuverability. The observed force balance indicates that DPIV can be used to measure accurately large-scale vorticity in the wake of swimming fishes and is therefore a valuable means of studying unsteady flows produced by animals moving through fluids.

Mechatronic Design and Maneuverability Analysis of a Novel Robotic Shark for Coral Reef Detection

2021 ◽  
Author(s):  
Liyang Gao ◽  
Peng Li ◽  
Hongde Qin ◽  
Zhongchao Deng
Keyword(s):  
Coral Reef ◽  
Dynamic Model ◽  
Swimming Speed ◽  
Three Dimensional ◽  
Pectoral Fin ◽  
Spiral Motion ◽  
Pectoral Fins ◽  
Mechatronic Design ◽  
Grid Technique ◽  
Turning Radius

Abstract In this paper, mechatronic design of a novel robotic shark for coral reef detection is presented. To obtain good maneuverability, a barycenter regulating device is designed to assist the posture adjustment of the robotic shark at low speed. Based on STAR-CCM+ software, the lift coefficients and drag coefficients of pectoral fin are calculated using overlapping grid technique. Based on Newton-Euler approach, a dynamic model with particular consideration of pectoral fins for three-dimensional motion is established. A CPG controller is used to generate rhythmic motion of each joint. Furthermore, based on the dynamic model, three-dimensional trajectory of spiral motion and swimming speed in different oscillation parameters are simulated. The results show that swimming speed of the robotic shark can be improved by increasing the amplitude and frequency or decreasing the phase difference. Also, oscillation frequency plays a more significant role. Furthermore, under the action of single pectoral fin, the robotic shark can achieve spiral motion and the turning radius is about 35.8m under the parameters set in this article.

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