Fish Locomotion Research Articles

Study of flexible fin and compliant joint stiffness on propulsive performance: theory and experiments

The caudal fin is a major source of thrust generation in fish locomotion. Along with the fin stiffness, the stiffness of the joint connecting the fish body to the tail plays a major role in the generation of thrust. This paper investigates the combined effect of fin and joint flexibility on propulsive performance using theoretical and experimental studies. For this study, fluid–structure interaction of the fin has been modeled using the 2D unsteady panel method coupled with nonlinear Euler–Bernoulli beam theory. The compliant joint has been modeled as a torsional spring at the leading edge of the fin. A comparison of self-propelled speed and efficiency with parameters such as heaving and pitching amplitude, oscillation frequency, flexibility of the fin and the compliant joint is reported. The model also predicts the optimized stiffnesses of the compliant joint and the fin for maximum efficiency. Experiments have been carried out to determine the effect of fin and joint stiffness on propulsive performance. Digital image correlation has been used to measure the deformation of the fins and the measured deformation is coupled with the hydrodynamic model to predict the performance. The predicted theoretical performance behavior closely matches the experimental values.

Effective Phase Tracking for Bioinspired Undulations of Robotic Fish Models: A Learning Control Approach

Robotic models have been used as one of the approaches to study fish locomotion. Therefore, this paper proposes an effective control scheme that enables robotic models to mimic fin-ray undulation kinematics of live fish. We found in the experiments of robotic fin undulation that the difference between the desired and actual trajectories can be significant. It is believed that the difference might be caused by the phase lagging effect. To tackle the phase tracking problem, a modified iterative learning control (ILC) scheme is proposed and implemented on the robotic fish model. Furthermore, a memory clearing operator is proposed to satisfy the Lipschitz condition. This is necessary for the convergence and feasibility of the ILC scheme. Finally, experimental results illustrate the effectiveness of the proposed learning control approach, including the memory clearing operator.

New Method of Fluid-structure Coupling in Self-propelled Swimming for Biomimetic Robotic Fish

A new method of fluid-structure coupling in self-propelled swimming for robotic fish is proposed from revealing the bionic mechanism inherent in the bionic shape and bionic movement for fish. The fluid and structural variables are simultaneously advanced in each iteration within the sub-iteration, and thus the stability of the algorithm is increased. The fish swimming medium has been divided into three mediums, including fluid medium, structural medium and the interface medium for which the kinetic equations are established. Given the fish kinematics as an input, the fish locomotion is transferred to the fluid grid to form an incentive on the surrounding fluid. The fluid forces are obtained by solving the fluid equations and will be transferred to fish to be treated as the external forces to drive the fish to swim freely. And thus the interaction of the fish and the fluid is achieved. Finally, the validity of the proposed method is verified by using the self-propulsion examples. This method can evaluate the good and bad performance for the robotic fish swimming with different shapes and different laws of motion, and provide scientific basis to reveal bionic swimming mechanism.

Numerical Simulations of Fast-start Motions of Fish

Fast-start swimming is a very special and important type of locomotion of fish. Basically, fast-star motion can be classified into two types: C-type and S-type. It is generally thought that the C-type fast-start is adopted by fish for escape while the S-type fast-start is used in prey capture. Previous experimental data have shown that the maximum acceleration and maximum velocity of fish performing C-start are significantly greater than that for S-type motion. The present research investigates numerically the fluid flows generated by empirically modeled fast-start movements of fish. For simplicity, a 2-D potential flow is assumed, and the unsteady Kutta condition is applied to handle the vortex-shedding phenomenon at fish tail. The panel method is adopted to solve the flow field numerically, and the force and moment acting on fish body are calculated by using the unsteady Bernoulli equation. Once the force and moment acting on fish are obtained at each instant, motion of fish can then be tracked by applying Newton's second law. Effects of force and moment exerting on fish, the moving speed and distance traveled by fish under different types of S-start and C-start movements are compared and discussed. Also presented are the fluid-dynamics interpretation of the fast-start motions and explanation of key mechanisms that lead to different performances of S-start and C-start modes. Basically in S-start mode, fish receives significant thrust from the momentum of accelerating fluid enhanced by the starting vortex near its tail. While in C-start mode, fish speeds up via a turning motion induced by the fluid force and moment acting on it. Since in C-start mode, fish utilizes the lateral force and moment to assist its turning and speeding rather than resists them, fish moving with C-start mode has faster moving speed and better efficiency of performance than with S-start mode. This can explain why fish normally adopt C-type fast-start mode in their attempt to escape from danger.

Bio-harmonized Dynamic Model of a Biology Inspired Carangiform Robotic Fish Underwater Vehicle

This paper presents a novel dynamic model of a bio-inspired robotic fish underwater vehicle by unifying conventional rigid body dynamics and bio-fluid-dynamics of a carangiform fish swimming given by Lighthill's (LH) slender body theory It proposes an inclusive mathematical design for better control and energy efficient path travel for the robotic fish. The system is modeled as an 2-link robot manipulator (caudal tail) with a mobile base (head). Lighthill caudal-tail reactive forces and moments are shown to contribute towards thrust generation and yaw balance. These LH reactive forces are shown to generate the inertial added mass during the robotic fish locomotion. This forward thrust drives the robotic fish head represented by a unified non-linear equation of motion in earth fixed frame. Using the proposed dynamic model an open-loop (manual) operating region for the identified kinematic parameter tail beat frequency (TBF) is established. Obtained Kinematic results also resemble with real fish kinematic results. The objective is to mimic the propulsion technique of the carangiform swimming style and to show the fish behavior navigating efficiently over large distances at impressive speeds and its exceptional character in fluid environment.

Three-dimensional swimming robotic fish with slide-block structure: design and realization

SUMMARYThis paper focuses on the mechanism design of a slide-block structure and its application on a biomimetic modular robotic fish for three-dimensional swimming. First, as a barycenter-adjustor, the slide-block structure is integrated into a mechanical design of a robotic fish, which is constructed by a control module, a driving module, and a fan-shaped caudal fin. The three-dimensional locomotion of robotic fish is decomposed into two-dimensional locomotion in horizontal plane and ascent–descent locomotion in vertical plane. Both the kinematics of the horizontal swim and the dynamics of the ascent–descent swim are analyzed by the curve fitting method. Finally, experimental results validate the three-dimensional swimming capability of the robotic fish. Furthermore, the impact of two design parameters on the swimming capability of the robotic fish is discussed by the experimental method. The experimental results confirm that the robotic fish with one driving module and a fan-shaped low-aspect-ratio caudal foil can produce higher propulsive speed than other parameter combinations.

Understanding undulatory locomotion in fishes using an inertia-compensated flapping foil robotic device

Recent advances in understanding fish locomotion with robotic devices have included the use of flapping foil robots that swim at a constant swimming speed. However, the speed of even steadily swimming live fishes is not constant because the fish center of mass oscillates axially throughout a tail beat cycle. In this paper, we couple a linear motor that produces controlled oscillations in the axial direction to a robotic flapping foil apparatus to model both axial and side to side oscillatory motions used by freely-swimming fishes. This experimental arrangement allows us to compensate for the substantial inertia of the carriage and motors that drive the oscillating foils. We identify a ‘critically-oscillated’ amplitude of axial motion at which the cyclic oscillations in axial locomotor force are greatly reduced throughout the flapping cycle. We studied the midline kinematics, power consumption and wake flow patterns of non-rigid foils with different lengths and flexural stiffnesses at a variety of axial oscillation amplitudes. We found that ‘critically-oscillated’ peak-to-peak axial amplitudes on the order of 1.0 mm and at the correct phase are sufficient to mimic center of mass motion, and that such amplitudes are similar to center of mass oscillations recorded for freely-swimming live fishes. Flow visualization revealed differences in wake flows of flexible foils between the ‘non-oscillated’ and ‘critically-oscillated’ states. Inertia-compensating methods provide a novel experimental approach for studying aquatic animal swimming, and allow instrumented robotic swimmers to display center of mass oscillations similar to those exhibited by freely-swimming fishes.

Minimal effects of waterborne exposure to single-walled carbon nanotubes on behaviour and physiology of juvenile rainbow trout (Oncorhynchus mykiss)

Fish behaviours are often considered to be sensitive endpoints of waterborne contaminants, but little attention has been given to engineered nanomaterials. The present study aimed to determine the locomotor and social behaviours of rainbow trout (Oncorhynchus mykiss) during waterborne exposure to single-walled carbon nanotubes (SWCNTs), and to ascertain the physiological basis for any observed effects. Dispersed stock suspensions of SWCNTs were prepared by stirring in sodium dodecyl sulphate (SDS), an anionic surfactant, on an equal w/w basis. Trout were exposed to control (no SWCNT or SDS), 0.25mgL−1 SDS (dispersant control), or 0.25mgL−1 of SWCNT for 10 days. Video tracking analysis of spontaneous locomotion of individual fish revealed no significant effects of SWCNT on mean velocity when active, total distance moved, or the distribution of swimming speeds. Hepatic glycogen levels were also unaffected. Fish exposed to SWCNTs retained competitive fitness when compelled to compete in energetically costly aggressive interactions with fish from both control groups. Assessment of the respiratory physiology of the fish revealed no significant changes in ventilation rate or gill injuries. Haematocrit and haemoglobin concentrations in the blood were unaffected by SWCNT exposure; and the absence of changes in the red and white pulp of the spleen excluded a compensatory haematopoietic response to protect the circulation. Despite some minor histological changes in the kidneys of fish exposed to SWCNT compared to controls, plasma ion concentrations and tissue electrolytes were largely unaffected. Direct neurotoxicity of SWCNT was unlikely with the brains showing mostly normal histology, and with no effects on acetylcholinesterase or Na+/K+-ATPase activities in whole brain homogenates. The minimal effects of waterborne exposure to SWCNT observed in this study are in contrast to our previous report of SWCNT toxicity in trout, suggesting that details of the dispersion method and co-exposure concentration of the dispersing agent may alter toxicity.

Monitoring Escape and Feeding Behaviours of Cruiser Fish by Inertial and Magnetic Sensors

A method was developed and applied for monitoring two types of fast-start locomotion (feeding and escape) of a cruiser fish, Japanese amberjacks Seriola quinqueradiata. A data logger, which incorporated a 3-axis gyroscope, a 3-axis accelerometer and a 3-axis magnetometer, was attached to the five fish. The escape, feeding and routine movements of the fish, which were triggered in tank experiments, were then recorded by the data logger and video cameras. The locomotor variables, calculated based on the high resolution measurements by the data logger (500 Hz), were investigated to accurately detect and classify the types of fast-track behaviour. The results show that fast-start locomotion can be detected with a high precision (0.97) and recall rate (0.96) from the routine movements. Two types of fast-start movements were classified with high accuracy (0.84). Accuracy was greater if the data were obtained from the data logger, which combined an accelerometer, a gyroscope and a magnetometer, than if only an accelerometer (0.80) or a gyroscope (0.66) was used.

Simulation Platform for Fishlike Swimming

Computational fluid dynamics (CFD) technique is considered as an effective approach for analysis of fishlike swimming, which quantitatively visualizes interaction between fishes and their fluid environment. This paper proposed and developed a simulation environment for understanding fish locomotion and hydrodynamic effects during the self-propulsion in a flow field. Approximate kinetic model or/and shape description based camera observation are recommended to specify active deformation of the body. Burst-Coast swimming is analyzed as an illustration of the simulation platform.

Evidence of trophic transfer of microcystins from the gastropod Lymnaea stagnalis to the fish Gasterosteus aculeatus

According to our previous results the gastropod Lymnaea stagnalis exposed to MC-producing cyanobacteria accumulates microcystins (MCs) both as free and covalently bound forms in its tissues, therefore representing a potential risk of MC transfer through the food web. This study demonstrates in a laboratory experiment the transfer of free and bound MCs from L. stagnalis intoxicated by MC-producing Planktothrix agardhii ingestion to the fish Gasterosteus aculeatus. Fish were fed during five days with digestive glands of L. stagnalis containing various concentrations of free and bound MCs, then with toxin-free digestive glands during a 5-day depuration period. MC accumulation was measured in gastropod digestive gland and in various fish organs (liver, muscle, kidney, and gills). The impact on fish was evaluated through detoxification enzyme (glutathion-S-transferase, glutathion peroxydase and superoxyde dismutase) activities, hepatic histopathology, and modifications in gill ventilation, feeding and locomotion. G. aculeatus ingestion rate was similar with intoxicated and toxin-free diet. Fish accumulated MCs (up to 3.96±0.14μgg−1DW) in all organs and in decreasing order in liver, muscle, kidney and gills. Hepatic histopathology was moderate. Glutathion peroxydase was activated in gills during intoxication suggesting a slight reactive oxygen species production, but without any impact on gill ventilation. Intoxication via ingestion of MC-intoxicated snails impacted fish locomotion. Intoxicated fish remained significantly less mobile than controls during the intoxication period possibly due to a lower health condition, whereas they showed a greater mobility during the depuration period that might be related to an acute foraging for food. During depuration, MC elimination was total in gills and kidney, but partial in liver and muscle. Our results assess the MC transfer from gastropods to fish and the potential risk induced by bound MCs in the food web.

The Construction of a Biomimetic Mobile Underwater Robot

This article presents the concept and construction of a mobile underwater robot. The robot is designed to work on battery power (cordless) and its movement systems is design after fish locomotion. The robot is propelled using fins which allow it to emerge submerge and move in a water environment. The robot is controlled using a remote control panel which communicates with the main control unit inside the robot

Proteomic profiling of sea bass muscle by two-dimensional gel electrophoresis and tandem mass spectrometry

In this study, the proteome profile of European sea bass (Dicentrarchus labrax) muscle was analyzed using two-dimensional electrophoresis (2-DE) and tandem mass spectrometry with the aim of providing a more detailed characterization of its specific protein expression profile. A highly populated and well-resolved 2-DE map of the sea bass muscle tissue was generated, and the corresponding protein identity was provided for a total of 49 abundant protein spots. Upon Ingenuity Pathway Analysis, the proteins mapped in the sea bass muscle profile were mostly related to glycolysis and to the muscle myofibril structure, together with other biological activities crucial to fish muscle metabolism and contraction, and therefore to fish locomotor performance. The data presented in this work provide important and novel information on the sea bass muscle tissue-specific protein expression, which can be useful for future studies aimed to improve seafood traceability, food safety/risk management and authentication analysis. This work is also important for understanding the proteome map of the sea bass toward establishing the animal as a potential model for muscular studies.

X-ray motion analysis of the vertebral column during the startle response in striped bass,Morone saxatilis

Whole-body stiffness has a substantial impact on propulsive wave speed during axial undulatory locomotion in fishes. The connective tissues of the vertebral column may contribute to body stiffness, but without mechanical and kinematic analysis it is unclear whether the in vivo range of motion of intervertebral joints (IVJs) is great enough to stress IVJ tissues, thus generating stiffness. The present study used 2D videoradiography and 3D X-ray reconstruction of moving morphology (XROMM) to quantify vertebral kinematics during the startle response in striped bass (Morone saxatilis). X-ray video revealed two distinct patterns of bending: pattern I begins in the abdominal region and then proceeds to maximum IVJ angles in the caudal region, whereas pattern II begins in the cervical region and proceeds to maximum IVJ angles in the abdominal and then the caudal joints. In pattern II bends, the cervical joints exhibit a greater in vivo range of motion than previously reported in other species. XROMM analysis of caudal IVJs suggests primarily lateral bending: mean axial and dorsoventral rotations were less than 2 deg and inconsistent across 51 sequences analyzed from five individuals, whereas mean maximum lateral bending angles were 10.4±3.57 deg. These angles, combined with previous investigations of mechanical properties, reveal that the maximum angles all occur within the neutral zone of bending, indicating that little stress is experienced about the joint. This suggests that the IVJs of striped bass are quite compliant and likely do not contribute significantly to whole-body stiffness or elastic recoil during swimming in vivo.

SEEING AND COMMUNICATING THROUGH WEAK ELECTRIC FIELDS

![][1] Weakly electric fish spend their lives bathed in their own internally generated mild electric field, interpreting perturbations in the field as objects pass through and when communicating with members of their own species through high frequency electric ‘chirps’. Rudiger

Note on the swimming of an elongated body in a non-uniform flow

AbstractThis paper presents an extension of Lighthill’s large-amplitude elongated-body theory of fish locomotion which enables the effects of an external weakly non-uniform potential flow to be taken into account. To do so, the body is modelled as a Kirchhoff beam, made up of elliptical cross-sections whose size may vary along the body, undergoing prescribed deformations consisting of yaw and pitch bending. The fluid velocity potential is decomposed into two parts corresponding to the unperturbed potential flow, which is assumed to be known, and to the perturbation flow. The Laplace equation and the corresponding Neumann’s boundary conditions governing the perturbation velocity potential are expressed in terms of curvilinear coordinates which follow the body during its motion, thus allowing the boundary of the body to be considered as a fixed surface. Equations are simplified according to the slenderness of the body and the weakness of the non-uniformity of the unperturbed flow. These simplifications allow the pressure acting on the body to be determined analytically using the classical Bernoulli equation, which is then integrated over the body. The model is finally used to investigate the passive and the active swimming of a fish in a Kármán vortex street.

Fluid structure interaction of a morphed wind turbine blade

SUMMARY One serious challenge of energy systems design, wind turbines in particular, is the need to match the system operation to the variable load. This is so because system efficiency drops at off-design load. One strategy to address this challenge for wind turbine blades and obtain a more consistent efficiency over a wide load range, is varying the blade geometry. Predictable morphing of wind turbine blade in reaction to wind load conditions has been introduced recently. The concept, derived from fish locomotion, also has similarities to spoilers and ailerons, known to reduce flow separation and improve performance using passive changes in blade geometry. In this work, we employ a fully coupled technique on CFD and FEM models to introduce continuous morphing to desired and predetermined blade design geometry, the NACA 4412 profile, which is commonly used in wind turbine applications. Then, we assess the aerodynamic behavior of a morphing wind turbine airfoil using a two-dimensional computation. The work is focused on assessing aerodynamic forces based on trailing edge deflection, wind speed, and material elasticity, that is, Young's modulus. The computational results suggest that the morphing blade has superior part-load efficiency over the rigid NACA blade. Copyright © 2013 John Wiley & Sons, Ltd.

Learning to see: Guiding students' attention via a Model's eye movements fosters learning

This study investigated how to teach perceptual tasks, that is, classifying fish locomotion, through eye movement modeling examples (EMME). EMME consisted of a replay of eye movements of a didactically behaving domain expert (model), which had been recorded while he executed the task, superimposed onto the video stimulus. Seventy-five students were randomly assigned to one of three conditions: In two experimental conditions (EMME) the model's eye movements were superimposed onto the video either as a dot or as a spotlight, whereas the control group studied only the videos without the model's eye movements. In all conditions, students listened to the expert's verbal explanations. Results showed that both types of EMME guided students' attention during example study. Subsequent to learning, students performed a classification task for novel test stimuli without any support. EMME improved visual search and enhanced interpretation of relevant information for those novel stimuli compared to the control group; these effects were further moderated by the specific display. Thus, EMME during training can foster learning and improve performance on novel perceptual stimuli.

Brain‐encysting trematodes and altered monoamine activity in naturally infected killifishFundulus parvipinnis

This paper presents novel evidence to address mechanisms by which trematode parasites effect behavioural changes in naturally infected fish hosts. California killifish Fundulus parvipinnis infected with the brain-encysting trematode Euhaplorchis californiensis display conspicuous swimming behaviours that render them 30 times more likely to be eaten by birds, the parasite's final host. Prevalence of E. californiensis reaches nearly 100% in most F. parvipinnis populations, with parasite biomass constituting almost 2% of F. parvipinnis biomass in some locations. Despite having thousands of cysts on their brains, infected fish grow and mature at rates comparable to those of uninfected populations. The lack of general pathology combined with the specificity of the altered behaviours suggests that the behavioural changes are due to parasite manipulation. The monoamine neurotransmitters serotonin and dopamine, which control locomotion and social behaviour in fishes and other vertebrates, were examined to explore the underlying mechanisms of this behaviour modification. Whereas previous studies were similarly conducted with experimentally infected fish, in this study, brain dopaminergic and serotonergic activity were analysed in naturally infected fish to assess how E. californiensis may alter F. parvipinnis monoamines in a naturally occurring system. A parasite density-associated decrease in serotonergic activity occurred in the hippocampus of naturally infected fish, as well as a decrease in dopaminergic activity in the raphe nuclei, suggesting that E. californiensis inhibits serotonin and dopamine signaling in naturally infected F. parvipinnis. The neurochemical profile of infected fish is consistent with the hypothesis that E. californiensis affects brain monoaminergic systems in order to induce impulse-driven, active, and aggressive behaviour in its hosts.

Optimal energy-utilization ratio for long-distance cruising of a model fish

The efficiency of total energy utilization and its optimization for long-distance migration of fish have attracted much attention in the past. This paper presents theoretical and computational research, clarifying the above well-known classic questions. Here, we specify the energy-utilization ratio (f(η)) as a scale of cruising efficiency, which consists of the swimming speed over the sum of the standard metabolic rate and the energy consumption rate of muscle activities per unit mass. Theoretical formulation of the function f(η) is made and it is shown that based on a basic dimensional analysis, the main dimensionless parameters for our simplified model are the Reynolds number (Re) and the dimensionless quantity of the standard metabolic rate per unit mass (R(pm)). The swimming speed and the hydrodynamic power output in various conditions can be computed by solving the coupled Navier-Stokes equations and the fish locomotion dynamic equations. Again, the energy consumption rate of muscle activities can be estimated by the quotient of dividing the hydrodynamic power by the muscle efficiency studied by previous researchers. The present results show the following: (1) When the value of f(η) attains a maximum, the dimensionless parameter R(pm) keeps almost constant for the same fish species in different sizes. (2) In the above cases, the tail beat period is an exponential function of the fish body length when cruising is optimal, e.g., the optimal tail beat period of Sockeye salmon is approximately proportional to the body length to the power of 0.78. Again, the larger fish's ability of long-distance cruising is more excellent than that of smaller fish. (3) The optimal swimming speed we obtained is consistent with previous researchers' estimations.