The Mechanics of Labriform Locomotion I. Labriform Locomotion in the Angelfish (Pterophyllum Eimekei): An Analysis of the Power Stroke

1979 ◽  
Vol 82 (1) ◽  
pp. 255-271
Author(s):  
R. W. BLAKE
Keyword(s):  
Total Energy ◽  
Thrust Force ◽  
The Body ◽  
Power Stroke ◽  
Pectoral Fin ◽  
Propulsive Efficiency ◽  
Rate Of Increase ◽  
Element Approach ◽  
Total Thrust ◽  
Recovery Stroke

1. A blade-element approach is used to analyse the mechanics of the drag-based pectoral fin power stroke in an Angelfish in steady forward, rectilinear progression. 2. Flow reversal occurs at the base of the fin at the beginning and at the end of the power stroke. Values for the rate of increase and decrease in the relative velocity of the blade-elements increase distally, as do such values for hydrodynamical angle of attack. At the beginning and end of the power stroke, negative angles occur at the base of the fin. 3. The outermost 40% of the fin produces over 80% of the total thrust produced during the power stroke, and doe8 over 80% of the total work. Small amounts of reversed thrust are produced at the base of the fin during the early and late parts of the stroke. 4. The total amount of energy required during a cycle to drag the body and inactive fins through the water is calculated to be approximately 2.8 × 10−6 J and the total energy produced by the fins over the cycle (ignoring the recovery stroke) which is associated with producing the hydrodynamic thrust force, is about 1.0 × 10−5 J; which gives a propulsive efficiency of about 0.26. 5. The energy required to move the mass of a pectoral fin during the power stroke is calculated to be approximately 2.6 × 10−7 J. Taking this into account reduces the value of the propulsive efficiency by about 4% to about 0.25. The total energy needed to accelerate and decelerate the added mass associated with the fin is calculated and added to the energy required to produce the hydrodynamic thrust force and the energy required to move the mass of the fins; giving a final propulsive efficiency of 0.18.

Design and Dynamic Modeling of a Flexible Feathering Joint for Robotic Fish Pectoral Fins

2014 ◽  
Author(s):  
Sanaz Bazaz Behbahani ◽  
Xiaobo Tan
Keyword(s):  
Dynamic Model ◽  
Robotic Fish ◽  
Power Stroke ◽  
Hydrodynamic Drag ◽  
Pectoral Fin ◽  
Flexible Joint ◽  
Blade Element Theory ◽  
Pectoral Fins ◽  
Flexible Part ◽  
Recovery Stroke

In this paper, we propose a novel design for a pectoral fin joint of a robotic fish. This joint uses a flexible part to enable the rowing pectoral fin to feather passively and thus reduce the hydrodynamic drag in the recovery stroke. On the other hand, a mechanical stopper allows the fin to maintain its motion prescribed by the servomotor in the power stroke. The design results in net thrust even when the fin is actuated symmetrically for the power and recovery strokes. A dynamic model for this joint and for a pectoral fin-actuated robotic fish involving such joints is presented. The pectoral fin is modeled as a rigid plate connected to the servo arm through a pair of torsional spring and damper that describes the flexible joint. The hydrodynamic force on the fin is evaluated with blade element theory, where all three components of the force are considered due to the feathering degree of freedom of the fin. Experimental results on robotic fish prototype are provided to support the effectiveness of the design and the presented dynamic model. We utilize three different joints (with different sizes and different flexible materials), produced with a multi-material 3D printer, and measure the feathering angles of the joints and the forward swimming velocities of the robotic fish. Good match between the model predictions and experimental data is achieved, and the advantage of the proposed flexible joint over a rigid joint, where the power and recovery strokes have to be actuated at different speeds to produce thrust, is demonstrated.

scholarly journals Fluid Dynamics of Biomimetic Pectoral Fin Propulsion Using Immersed Boundary Method

2016 ◽  
Vol 2016 ◽  
pp. 1-22 ◽  
Author(s):  
Ningyu Li ◽  
Yumin Su
Keyword(s):  
Fluid Dynamics ◽  
Three Dimensional ◽  
Reconstruction Algorithm ◽  
Power Stroke ◽  
Hydrodynamic Characteristics ◽  
Ring Vortex ◽  
Immersed Boundary ◽  
Pectoral Fin ◽  
Local Flow ◽  
Recovery Stroke

Numerical simulations are carried out to study the fluid dynamics of a complex-shaped low-aspect-ratio pectoral fin that performs the labriform swimming. Simulations of flow around the fin are achieved by a developed immersed boundary (IB) method, in which we have proposed an efficient local flow reconstruction algorithm with enough robustness and a new numerical strategy with excellent adaptability to deal with complex moving boundaries involved in bionic flow simulations. The prescribed fin kinematics in each period consists of the power stroke and the recovery stroke, and the simulations indicate that the former is mainly used to provide the thrust while the latter is mainly used to provide the lift. The fin wake is dominated by a three-dimensional dual-ring vortex wake structure where the partial power-stroke vortex ring is linked to the recovery-stroke ring vertically. Moreover, the connection of force production with the fin kinematics and vortex dynamics is discussed in detail to explore the propulsion mechanism. We also conduct a parametric study to understand how the vortex topology and hydrodynamic characteristics change with key parameters. The results show that there is an optimal phase angle and Strouhal number for this complicated fin. Furthermore, the implications for the design of a bioinspired pectoral fin are discussed based on the quantitative hydrodynamic analysis.

Dynamic Analysis of a Robotic Fish Propelled by Flexible Folding Pectoral Fins

Robotica ◽  
2019 ◽  
Vol 38 (4) ◽  
pp. 699-718 ◽  
Author(s):  
Van Anh Pham ◽  
Tan Tien Nguyen ◽  
Byung Ryong Lee ◽  
Tuong Quan Vo
Keyword(s):  
Power Stroke ◽  
Swimming Velocity ◽  
Force Model ◽  
Flexible Joints ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
Recovery Stroke ◽  
Turning Radius ◽  
Relationship Of ◽  
The Relationship

SUMMARYBiological fish can create high forward swimming speed due to change of thrust/drag area of pectoral fins between power stroke and recovery stroke in rowing mode. In this paper, we proposed a novel type of folding pectoral fins for the fish robot, which provides a simple approach in generating effective thrust only through one degree of freedom of fin actuator. Its structure consists of two elemental fin panels for each pectoral fin that connects to a hinge base through the flexible joints. The Morison force model is adopted to discover the relationship of the dynamic interaction between fin panels and surrounding fluid. An experimental platform for the robot motion using the pectoral fin with different flexible joints was built to validate the proposed design. The results express that the performance of swimming velocity and turning radius of the robot are enhanced effectively. The forward swimming velocity can reach 0.231 m/s (0.58 BL/s) at the frequency near 0.75 Hz. By comparison, we found an accord between the proposed dynamic model and the experimental behavior of the robot. The attained results can be used to design controllers and optimize performances of the robot propelled by the folding pectoral fins.

scholarly journals Swimming of slender fish in a non-uniform velocity field

1975 ◽  
Vol 19 (1) ◽  
pp. 95-111 ◽  
Author(s):  
J. N. Newman
Keyword(s):  
Velocity Field ◽  
Thrust Force ◽  
Hydrodynamic Pressure ◽  
The Body ◽  
Uniform Field ◽  
Fish Swimming ◽  
Uniform Velocity ◽  
Turbulent Eddies ◽  
Fish Propulsion ◽  
Total Thrust

AbstractThe hydrodynamic pressure forces acting upon a slender fish are derived for the case of a fish swimming in a non-uniform velocity field. Possible applications are the effects on fish propulsion of swimming in waves, in turbulent eddies, and in the presence of other fish or a moving ship. The fish is assumed to be a slender body, with no vorticity shed into the fluid except at a single abrupt trailing edge located at the posterior end of the fish, and to be performing small lateral swimming undulations of its body. The non-uniform field through which the fish swims is assumed to be irrotational, and this field as well as the body undulations must be slowly-varying on the length-scale of the lateral fish dimensions. Expressions are derived for the local force and the time-averaged total thrust force. These are applied to the study of steady-state bow-riding and wave-riding of porpoises.

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.

Hydrodynamics of swimming in the water boatman, Cenocorixa bifida

1986 ◽  
Vol 64 (8) ◽  
pp. 1606-1613 ◽  
Author(s):  
R. W. Blake
Keyword(s):  
High Speed ◽  
Forward Direction ◽  
Added Mass ◽  
Mean Value ◽  
The Body ◽  
Power Stroke ◽  
Mass Force ◽  
Mean Power ◽  
Recovery Stroke ◽  
The Mean

Locomotion of a small water boatman (Cenocorixa bifida, Corixidae) was investigated employing high-speed cinematography and hydromechanical modelling based on a blade-element approach. The animal is propelled by the synchronous rowing action of its hind legs. The propulsive cycle consists of a power stroke and a recovery stroke phase. Force, impulse, power, and hydromechanical efficiency were calculated for a representative power stroke during which the mean body velocity was about 8 cms−1. A distinction is made between quasi-steady resistive and unsteady inertial (added mass) forces. The mean and maximum resistive thrust forces were calculated to be about 2.4 × 10−5 and 5.7 × 10−5 N per limb, respectively. By equating the total impulse of the power stroke for both legs (2.4 × 10−6 N s) with that of the drag force acting on the body over the same period, a drag coefficient of approximately 1.07 is inferred for the body. This value is comparable to those obtained for certain insects that operate at similar Reynolds numbers to C. bifida. The unsteady added mass force that acts in the forward direction is positive (propulsive) over most of the stroke with a mean value of about 1.17 × 10−5 N per limb, corresponding to an impulse of approximately 5.9 × 10−7Ns. The total propulsive mean force and impulse acting in the forward direction amount to about 3.6 × 10−5N and 1.8 × 10−6N s per limb, respectively, so the impulse of the forwardly directed added mass force amounts to about half that of the resistive thrust force. The total work and mean power associated with generating the resistive thrust were calculated to be about 6.7 × 10−7 J and 1.33 × 10−5 W per limb, respectively. Dividing the mean body drag power (1.4 × 10−5 W) by the total mean resistive power from both legs gave a hydromechanical efficiency of 0.52. When the mean inertial power associated with moving the body (2.3 × 10−6 W) and the added mass power required to accelerate and decelerate the legs (1.95 × 10−5 W per limb) are taken into account, the power stroke propulsive efficiency falls to 0.42. Taking the energy required to power the recovery stroke into account gives an overall propulsive cycle efficiency of about 0.40. This value is about twice that calculated in a previous study for drag-based pectoral fin rowing in the angelfish and reasons for this are suggested.

Does a rigid body limit maneuverability?

2000 ◽  
Vol 203 (22) ◽  
pp. 3391-3396 ◽  
Author(s):  
J.A. Walker
Keyword(s):  
Rigid Body ◽  
The Body ◽  
Alternative Measure ◽  
Pectoral Fin ◽  
Caudal Fin ◽  
Minimum Radius ◽  
Current Definition ◽  
Theoretical Minimum

Whether a rigid body limits maneuverability depends on how maneuverability is defined. By the current definition, the minimum radius of the turn, a rigid-bodied, spotted boxfish Ostracion meleagris approaches maximum maneuverability, i.e. it can spin around with minimum turning radii near zero. The radius of the minimum space required to turn is an alternative measure of maneuverability. By this definition, O. meleagris is not very maneuverable. The observed space required by O. meleagris to turn is slightly greater than its theoretical minimum but much greater than that of highly flexible fish. Agility, the rate of turning, is related to maneuverability. The median- and pectoral-fin-powered turns of O. meleagris are slow relative to the body- and caudal-fin-powered turns of more flexible fish.

Caudal Fin and Body Movement in the Propulsion of some Fish

1963 ◽  
Vol 40 (1) ◽  
pp. 23-56 ◽  
Author(s):  
RICHARD BAINBRIDGE
Keyword(s):  
Body Movement ◽  
Wave Length ◽  
The Body ◽  
Whole Body ◽  
Tail Region ◽  
Caudal Fin ◽  
A Value ◽  
Total Thrust ◽  
Transverse Movement ◽  
Relationship Of

1. Observations made on bream, goldfish and dace swimming in the ‘Fish Wheel’ apparatus are described. These include: 2. An account of the complex changes in curvature of the caudal fin during different phases of the normal locomotory cycle. Measurements of this curvature and of the angles of attack associated with it are given. 3. An account of changes in area of the caudal fin during the cycle of lateral oscillation. Detailed measurements of these changes, which may involve a 30 % increase in height or a 20 % increase in area, are given. 4. An account of the varying speed of transverse movement of the caudal fin under various conditions and the relationship of this to the changes in area and amount of bending. Details of the way this transverse speed may be asymmetrically distributed relative to the axis of progression of the fish are given. 5. An account of the extent of the lateral propulsive movements in other parts of the body. These are markedly different in the different species studied. Measurements of the wave length of this movement and of the rate of progression of the wave down the body are given. 6. It is concluded that the fish has active control over the speed, the amount of bending and the area of the caudal fin during transverse movement. 7. The bending of the fin and its changes in area are considered to be directed to the end of smoothing out and making more uniform what would otherwise be an intermittent thrust from the oscillating tail region. 8. Some assessment is made of the proportion of the total thrust contributed by the caudal fin. This is found to vary considerably, according to the form of the lateral propulsive movements of the whole body, from a value of 45% for the bream to 84% for the dace.

The Ligamentary System and the Segmental Musculature of Nephtys

1960 ◽  
Vol s3-101 (54) ◽  
pp. 149-176
Author(s):  
R. B. CLARK ◽  
M. E. CLARK
Keyword(s):  
Body Wall ◽  
The Body ◽  
Power Stroke ◽  
Coelomic Fluid ◽  
Unusual Structure ◽  
Shock Absorbers ◽  
Proximal Half ◽  
Unique System ◽  
Body Wall Muscles ◽  
The Impact

Nephtys lacks circular body-wall muscles. The chief antagonists of the longitudinal muscles are the dorso-ventral muscles of the intersegmental body-wall. The worm is restrained from widening when either set of muscles contracts by the combined influence of the ligaments, some of the extrinsic parapodial muscles, and possibly, to a limited extent, by the septal muscles. Although the septa are incomplete, they can and do form a barrier to the transmission of coelomic fluid from one segment to the next under certain conditions, particularly during eversion of the proboscis. Swimming is by undulatory movements of the body but the distal part of the parapodia execute a power-stroke produced chiefly by the contraction of the acicular muscles. It is suspected that the extrinsic parapodial muscles, all of which are inserted in the proximal half of the parapodium, serve to anchor the parapodial wall at the insertion of the acicular muscles and help to provide a rigid point of insertion for them. Burrowing is a cyclical process involving the violent eversion of the proboscis which makes a cavity in the sand. The worm is prevented from slipping backwards by the grip the widest segments have on the sides of the burrow. The proboscis is retracted and the worm crawls forward into the cavity it has made. The cycle is then repeated. Nephtys possesses a unique system of elastic ligaments of unusual structure. The anatomy of the system is described. The function of the ligaments appears to be to restrain the body-wall and parapodia from unnecessary and disadvantageous dilatations during changes of body-shape, and to serve as shock-absorbers against the high, transient, fluid pressures in the coelom, which are thought to accompany the impact of the proboscis against the sand when the worm is burrowing. From what is known of its habits, Nephtys is likely to undertake more burrowing than most other polychaetes.

scholarly journals Morphological development of larvae and juveniles of Prochilodus argenteus

2017 ◽  
Vol 47 (4) ◽  
Author(s):  
Irũ Menezes Guimarães ◽  
◽  
Vinícius Augusto Dias Filho ◽  
Ana Helena Gomes da Silva ◽  
Rafael Silva Santos ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Linear Regression Analysis ◽  
The Body ◽  
Morphological Development ◽  
Body Proportions ◽  
Juvenile Phase ◽  
Larval Stages ◽  
Larvae And Juveniles ◽  
Rate Of Increase ◽  
Environmental Importance

ABSTRACT: Prochilodus argenteus is an endemic fish species from the São Francisco River basin that is of high economic and environmental importance. The present study aimed to contribute with information to the taxonomic identification of larvae and juveniles of this species. Larvae , obtained from induced spawning of wild animals, were reared in ponds. Individuals were collected daily and classified into larval stages or juvenile phase. Morphological descriptions and morphometric measurements were performed, together with a piece wise linear regression analysis of the body proportions throughout the development process. Individuals in the preflexion stage had a standard length (SL) of 4.48 to 6.64mm, long to moderate body (BH/SL), small to moderate head (HL/SL), and a small to moderate eye (ED/HL). In the flexion stage, the SL varied from 6.60 to 11.00mm, long to moderate body, moderate head, and small to moderate eye. Larvae in the postflexion stage presented SL of 10.54-19.93mm, moderate body, moderate to big head and small eye. The juvenile phase included specimens with a SL of 18.27 to 42.21mm which presented a moderate to high body, big head and small to moderate eye. Regression analysis showed significant moments of change in rate of increase of the body proportions, presenting a change in the growth pattern from allometry to isometry during the early development.

Sign in / Sign up

Export Citation Format

Share Document