Body Swimming Research Articles

Relationship between different push-off variables and start performance in experienced swimmers

The objective of this study was to determine the relationship between different variables measured with a force plate during the swimming start push-off phase and start performance presented by times to 5, 10 and 15 m. Twenty-one women from the Slovenian national swimming team performed two different swim starts (freestyle and undulatory) on a portable force plate to a distance further than 15 m. Correlations between push-off variables and times to 5, 10 and 15 m were quantified through Pearson's product-moment correlation coefficient (r). The variables that significantly correlated (p < .05) to all times measured in the two starts performed were: average horizontal acceleration (freestyle: r = −0.58 to −0.71; and undulatory: r = −0.55 to −0.66), horizontal take-off velocity (freestyle: r = −0.56 to −0.69; and undulatory: r = −0.53 to −0.67) and resultant take-off velocity (freestyle: r = −0.53 to −0.65; and undulatory: r = −0.52 to −0.61). None of the variables derived from the vertical force were correlated to swimming start performance (p > .05). Based on the results of this study, we can conclude that horizontal take-off velocity and average horizontal acceleration (calculated as the average horizontal force divided by swimmer's body mass) are the variables most related to swimming start performance in experienced swimmers, and therefore could be the preferred measures to monitor swimmers’ efficiency during the push-off phase.

Adaptive body patterning, three-dimensional skin morphology and camouflage measures of the slender filefish Monacanthus tuckeri on a Caribbean coral reef.

The slender filefish is a master of adaptive camouflage and can change its appearance within 1-3 seconds. Videos and photographs of this animal's cryptic body patterning and behavior were collected in situ under natural light on a Caribbean coral reef. We present an ethogram of body patterning components that includes large- and small-scale spots, stripes and bars that confer a variety of cryptic patterns amidst a range of complex backgrounds. Field images were analyzed to investigate two aspects of camouflage effectiveness: (i) the degree of color resemblance between animals and their nearby visual stimuli and (ii) the visibility of each fish's actual body outline versus its illusory outline. Most animals more closely matched the color of nearby visual stimuli than that of the surrounding background. Three-dimensional dermal flaps complement the melanophore skin patterns by enhancing the complexity of the fish's physical skin texture to disguise its actual body shape, and the morphology of these structures was studied. The results suggest that the body patterns, skin texture, postures and swimming orientations putatively hinder both the detection and recognition of the fish by potential visual predators. Overall, the rapid speed of change of multiple patterns, color blending with nearby backgrounds, and the physically complicated edge produced by dermal flaps effectively camouflage this animal among soft corals and macroalgae in the Caribbean Sea.

Performance enhancement of a Lorentz force velocimeter using a buoyancy-compensated magnet system

Lorentz force velocimetry (LFV) is a highly feasible method for measuring flow rate in a pipe or a duct. This method has been established for liquid metal flows but also for electrolytes such as saltwater. A decrease in electrical conductivity of the medium causes a decrease of the Lorentz force which needs to be resolved, affecting the accuracy of the measurement. We use an electrical force compensation (EFC) balance for the determination of the tiny force signals in a test channel filled with electrolyte solution. It is used in a 90°-rotated orientation with a magnet system hanging vertically on its load bar. The thin coupling elements of its parallel guiding system limit the mass of the magnets to 1 kg. To overcome this restriction, which limits the magnetic flux density and hence the Lorentz forces, a weight force compensation mechanism is developed. Therefore, different methods such as air bearing are conceivable, but for the elimination of additional horizontal force components which would disturb the force signal, only compensation by lift force provided by buoyancy is reasonable. We present a swimming body setup that will allow larger magnet systems than before, because a large amount of the weight force will be compensated by this lift force. Thus the implementation of this concept has to be made with respect to hydrodynamical and mechanical stability. This is necessary to avoid overturning of the swimming body setup and to prevent inelastic deformation. Additionally, the issue will be presented and discussed whether thermal convection around the lifting body diminishes the signal-to-noise ratio (SNR) significantly or not.

Well-posedness of 2-D and 3-D swimming models in incompressible fluids governed by Navier–Stokes equations

We introduce and investigate the wellposedness of two models describing the self-propelled motion of a “small bio-mimetic swimmer” in the 2-D and 3-D incompressible fluids modeled by the Navier–Stokes equations. It is assumed that the swimmer's body consists of finitely many subsequently connected parts, identified with the fluid they occupy, linked by the rotational and elastic forces. The swimmer employs the change of its shape, inflicted by respective explicit internal forces, as the means for self-propulsion in a surrounding medium. Similar models were previously investigated in [15–19] where the fluid was modeled by the liner nonstationary Stokes equations. Such models are of interest in biological and engineering applications dealing with the study and design of propulsion systems in fluids and air.

Phylogenetics to help predict active metabolism

This paper shows how to build predictive models involving phylogenetic information to estimate metabolic traits such as active metabolic costs. Fish swimming cost is often estimated from body mass and swimming speed. The parameters of the relationships between these variables and swimming cost vary among species because each species has its own morphology and physiology. It is now widely recognized that traits are phylogenetically structured. Using new statistical approaches, it is possible to both correct swimming cost models for statistical phylogenetic non‐independence and use the inherent phylogenetic signal to improve models. With these models one can extend, to a larger set of species, empirical knowledge about traits that are difficult to obtain; swimming cost is one such trait.Swimming cost accounts for a large and variable component of a fish energy budget, yet models have only been developed from observations performed on a few species, thereby constraining the scope of bioenergetic models. Here, we propose a method where body mass and swimming speed are used together with phylogeny to predict swimming cost. The resulting model explained a large proportion of the variation (90%) in the forced swimming cost of 16 fish species submitted to forced swimming experiments. We also compared phylogenetically‐explicit predictions for forced swimming experiments with experimental results of routine swimming for five species, among which one was not used to build the model. Results confirmed that forced swimming underestimates the cost of unsteady swimming. The phylogenetic modeling could be used to estimate other variables of interest in bioenergetic studies.

Assimilating to a boy’s body shape for the sake of performance: three female athletes’ body experiences in a sporting culture

This paper explores three female swimmers’ relationships with their male coaches and the body practices they were exposed to within Australian swimming. Particular attention is given to how the relationships and practices might relate to gender. Additionally, the article examines how (if at all) the conduct contributed to the social construction of an accepted female swimmer body. Through narrative accounts, the three adolescent female athletes articulate hierarchical male coach–female athlete relationships and specific body encounters they were exposed to and/or engaged with. Their experiences reveal how a sexually maturing body (growing breasts, female body shape and menstruating) was deemed unsuitable for performance and the swimmers were thus encouraged to transform their bodies and behaviours towards that of the boys. Using a feminist Foucauldian perspective, these accounts points to how the three swimmers came to regulate their diet, training and appearance in order to fulfil expectations. This self-regulation is problematic in two ways: first, no scientific evidence shows that a boy like physique is essential for best performance. Second, the stress from being pressured to achieve a particular body, as well as the shame that resulted from being unable to achieve the idealised physique, eventually caused the swimmers to develop an unhealthy relationship with their developing bodies. We highlight how those immersed in sporting contexts should recognise the serious implications of gender practices and power relations underpinning the male coach–female athlete dynamic in competitive sport.

Hydrodynamic body shape analysis and their impact on swimming performance.

This study presents the hydrodynamic characteristics of different adult male swimmer's body shape using computational fluid dynamics method. This simulation strategy is carried out by CFD fluent code with solving the 3D incompressible Navier-Stokes equations using the RNG k-ε turbulence closure. The water free surface is captured by the volume of fluid (VOF) method. A set of full body models, which is based on the anthropometrical characteristics of the most common male swimmers, is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. The analysis of CFD results revealed that swimmer's body shape has a noticeable effect on the hydrodynamics performances. This explains why male swimmer with an inverted triangle body shape has good hydrodynamic characteristics for competitive swimming.

Sasa borealis Extract Efficiently Enhanced Swimming Capacity by Improving Energy Metabolism and the Antioxidant Defense System in Mice.

This study was conducted to determine the effects of 50% ethanolic extract from Sasa borealis leaves (SBE) on swimming capacity and oxidative metabolism in mice. The mice were divided into 2 groups with similar swimming times and body weights; Ex-Control and Ex-SBE were orally administered with distilled water and 250 mg/kg body weight/d of SBE. Exhaustive swimming times were prolonged by 1.5-fold in the Ex-SBE group compared to the Ex-Control. The Ex-SBE group displayed lower lactate and higher non-esterified fatty acid levels 15 min after swimming and the hepatic and muscle glycogen levels were significantly higher than that in the Ex-Control. SBE potentially enhanced mRNA expression of citrate synthase (CS), carnitine palmitoyltransferase (CPT-1), and β-hydroxyacyl coenzyme A dehydrogenase (β-HAD) in skeletal muscle. The activities and mRNA expression of catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were elevated in the Ex-SBE compared with the Ex-Control after exhaustive swimming. These results suggest that SBE might be used as an effective agent to enhance swimming capacity by utilization of energy substrates and might ameliorate physical exhaustion by facilitating energy-generating metabolic genes and enhancing endogenous antioxidants.

Nano-tags for neonates and ocean-mediated swimming behaviours linked to rapid dispersal of hatchling sea turtles.

Dispersal during juvenile life stages drives the life-history evolution and dynamics of many marine vertebrate populations. However, the movements of juvenile organisms, too small to track using conventional satellite telemetry devices, remain enigmatic. For sea turtles, this led to the paradigm of the 'lost years' since hatchlings disperse widely with ocean currents. Recently, advances in the miniaturization of tracking technology have permitted the application of nano-tags to track cryptic organisms. Here, the novel use of acoustic nano-tags on neonate loggerhead turtle hatchlings enabled us to witness first-hand their dispersal and behaviour during their first day at sea. We tracked hatchlings distances of up to 15 km and documented their rapid transport (up to 60 m min(-1)) with surface current flows passing their natal areas. Tracking was complemented with laboratory observations to monitor swimming behaviours over longer periods which highlighted (i) a positive correlation between swimming activity levels and body size and (ii) population-specific swimming behaviours (e.g. nocturnal inactivity) suggesting local oceanic conditions drive the evolution of innate swimming behaviours. Knowledge of the swimming behaviours of small organisms is crucial to improve the accuracy of ocean model simulations used to predict the fate of these organisms and determine resultant population-level implications into adulthood.

Body movement distribution with respect to swimmer’s glide position in human underwater undulatory swimming

Human swimmers use undulatory motions similar to fish locomotion to attain high speeds. The human body is a non-smooth multi-body linkage system with restricted flexibility and is not primarily adapted to motion in the water. Due to anatomical limitations, the human swimmer is forced to deviate from the symmetric fish-like motion and to adjust his motion to his limited abilities. The goal of this paper is to investigates the movement of ten swimmers during human underwater undulatory in a still water pool and to find out to what extent the human swimmer approaches an ideal undulatory wave which is symmetric with respect to the extended gliding position. Therefore, it is necessary to (i) to ascertain the magnitude of the normalized dorsal, ventral and total amplitudes of the undulatory movements, (ii) to examine the distribution and symmetry/asymmetry of the dorsal, ventral and total amplitudes along the length of the swimming body, and (iii) to compare the differences in amplitude distribution and other indicators between different skill levels. The amplitude distribution of the dorsal and ventral deflection along the body (related to the swimmer’s stretched position) is highly asymmetric. Skilled swimmers swim with a more linear body wave and use a smaller range of envelop than less skilled swimmers. The durations of the up and down kicks show only minor differences. The down kick is slightly faster than the up kick. Although the down kick is more powerful than the up kick, the hip marker shows almost the same average swimming speed in both half-cycles.

Passive drag reduction using full-body swimsuits: the role of body position.

This study aimed to analyze whether using full-body swimsuits affects the swimmer's body alignment and to what extent changes in the body position are responsible of the passive drag (Dp) reduction experienced by the swimmers when using these swimsuits. Fourteen swimmers performed 20-m towing trials using a full-body synthetic rubber swimsuit, a full-body textile swimsuit, a traditional brief swimsuit, and a traditional brief swimsuit with a pull buoy. In all trials, the speed-specific drag (k = Dp per v), the trunk incline (TI), and the lower limbs incline (LI) were determined. In comparison with both conditions in which a full-body swimsuit was not used, k was significantly lower when using the rubber swimsuit (-8.4 and -12.2% vs. the brief swimsuit with and without pull bouy, respectively), and the textile swimsuit (-6.9 and -10.8% vs. the brief swimsuit with and without pull bouy, respectively). No differences in TI were observed among conditions, whereas LI was significantly higher when using the rubber swimsuit or the brief swimsuit with pull buoy than when using the traditional brief swimsuit. A linear mixed model showed that k can be reduced by increasing LI (that is lifting the lower limbs), by decreasing TI (that is keeping the trunk more horizontal), and by using either the rubber or textile full-body swimsuit rather than the traditional brief swimsuit. In conclusion, full-body swimsuits involve a reduction of a swimmer's passive drag caused by intrinsic properties related to the "material composition" of the swimsuits and also influenced by changes in the swimmer's body position.

Characterization and Modeling of Biomimetic Untethered Robots Swimming in Viscous Fluids Inside Circular Channels

Miniaturized robots with bioinspired propulsion mechanisms, such as rotating helical flagella, are promising tools for minimally invasive surgery, diagnosis, targeted therapy, drug delivery, and removing material from the human body. Understanding the locomotion of swimmers inside fluid-filled channels is essential for the design and control of miniaturized robots inside arteries and conduits of living organisms. In this paper, we describe scaled-up experiments and modeling of untethered robots with a rotating helical tail and swimming inside a tube filled with a viscous fluid. Experiments mimic low Reynolds number swimming of miniaturized robots inside conduits filled with aqueous solutions. A capsule that contains the battery and a small dc motor is used for the body of the robots. Helical tails with different geometric parameters are manufactured and used to obtain swimming speeds and body rotation rates of robots inside the cylindrical channel. Three-dimensional incompressible flow around the robot inside the channel is governed by Stokes equations, which are solved numerically with a computational fluid dynamics (CFD) model. Predicted velocities of robots are compared with the experimental results for the validation of the CFD model, which is used to analyze effects of the helical radius, pitch, and the radial position of the robot on the swimming speed, forces acting on the robot, and efficiency.

Development toxicity of functionalized single-walled carbon nanotubes on rare minnow embryos and larvae

Carbon nanotubes (CNTs) are widely used in industrial and commercial applications, but few studies systematically evaluate their developmental toxicity on aquatic organism. Using rare minnow (Gobiocypris rarus) at early life stages as experimental models, developmental toxicity of functionalized single-walled CNTs (SWCNTs) was investigated following exposure to 0–320 mg/L for 144 h. Results revealed that significantly increased in mortality and malformation was only observed after hatching. Decreased body length, heart rate and swimming speed provide a concentration-dependent manner on larvae; values of 144 h LC50 and EC50 were 140.8 and 109.8 mg/L, respectively. Antioxidant enzyme activities (superoxide dismutase, catalase and glutathione S-transferase) and antioxidant enzyme related mRNA expressions were significant changed; cell apoptosis activities (caspase-3, -8, -9) and cell apoptosis related mRNA expressions were significant up-regulated; reactive oxygen species and DNA damage were significantly induced when the concentration of SWCNTs above 100 mg/L. Fluorescence and electron microscopy sliced observation show that SWCNTs were well dispersed in larvae within 0.5 h, eventually cleared from the larvae at 144 h. This is the first study to define uptake kinetics and to focus on behavioral consequences, physiological changes and mRNA expression following SWCNTs exposure in the early life stages of fish. The results obtained in the present study demonstrated that functionalized SWCNTs have the potential to affect aquatic life when released into the aquatic environment and reached high concentration. In the increasing economical context of SWCNTs, complementary studies must be undertaken, especially including mechanistic and environmental investigations.

Measurement of swimming pattern and body length of cultured Chinese sturgeon by use of imaging sonar

Abstract Measurement of fish length and assessment of behavior are important to fish farming, but it can be a practical challenge. In this study, an acoustic camera (Dual-frequency Identification Sonar, DIDSON) was used to observe the swimming pattern of 10 cultured Chinese sturgeon ( Acipenser sinensis ) in a net cage, and to estimate their length. In total, 2743 targets were identified from DIDSON data collected over 12 h. Target tracking indicated that most fish swam close to the net in a circular motion, at mean speed of 0.7 ± 0.3 m s − 1 . The length (95.2 ± 25.0 cm) of the targets measured through the DIDSON was 35.6% shorter than the total length from manual measurements (147.9 ± 9.3 cm), although the maximum lengths found by both methods were similar. Swimming pattern had a considerable influence on the accuracy of target length estimation. Accordingly, it was essential to select the targets based on swimming behavior to achieve more accurate length estimates. This study proposes that the acoustic camera is a valuable tool for investigating the behavior of the cultured fish and for estimating their length. However, designs for system installation and the net cage should be enhanced.

PENGARUH PENCEMARAN LOGAM BERAT TERHADAP STRUKTUR POPULASI DAN ORGAN TUBUH RAJUNGAN (Portunus pelagicus, LINN)

Blue Swimming crab ( Portunus pelagicus ) is one of important fishery in Indonesia that captured nearshore on the bottom of the sea. There has been a significant water contamination on the Jakarta bay and the fishery are reported to be effected. Many heavy metals and other contaminants are introduced into the waters, sediments, and fishery that living in the bay. Heavy metals such as Pb, Cd, Hg and As are the most lethal contaminants and found in Jakarta Bay. This study aims to determine the effect of heavy metals contaminants to the blue swimming crab morphometric, body organs and population structure of blue swimming crabs in Jakarta bay, which compared to the study in healthier environment in Madura island. The results of this study showed that 1) The morphometric parameter of blue swimming crab population in Jakarta and Madura are significantly different. 2) The internal organ of the blue swimming crab (hepatopancreas, gonad and gill) in Jakarta bay are also significantly different than in Madura. The histological analysis are confirmed some abnormal indication of the internal body of the blue swimming crab in Jakarta bay.3) Some population parameters of the blue swimming crab in jakarta bay are significantly different than in Madura island. The fishery structure in Jakarta bay showed the size of first maturity of the crabs is relatively smaller than in Madura and other area of Inodonesia. The fishery mangament based on spatial area management is recommended to apply in different area of Indonesia. Keywords: heavy metal contamination, blue swimming crab

Behavioral Analysis of Cuttlefish Traveling Waves and Its Implications for Neural Control

Traveling waves (from action potential propagation to swimming body motions or intestinal peristalsis) are ubiquitous phenomena in biological systems and yet are diverse in form, function, and mechanism. An interesting such phenomenon occurs in cephalopod skin, in the form of moving pigmentation patterns called "passing clouds". These dynamic pigmentation patterns result from the coordinated activation of large chromatophore arrays. Here, we introduce a new model system for the study of passing clouds, Metasepia tullbergi, in which wave displays are very frequent and thus amenable to laboratory investigations. The mantle of Metasepia contains four main regions of wave travel, each supporting a different propagation direction. The four regions are not always active simultaneously, but those that are show synchronized activity and maintain a constant wavelength and a period-independent duty cycle, despite a large range of possible periods (from 1.5 s to 10 s). The wave patterns can be superposed on a variety of other ongoing textural and chromatic patterns of the skin. Finally, a traveling wave can even disappear transiently and reappear in a different position ("blink"), revealing ongoing but invisible propagation. Our findings provide useful clues about classes of likely mechanisms for the generation and propagation of these traveling waves. They rule out wave propagation mechanisms based on delayed excitation from a pacemaker but are consistent with two other alternatives, such as coupled arrays of central pattern generators and dynamic attractors on a network with circular topology.

Pengaruh Pencemaran Logam Berat Terhadap Struktur Populasi dan Organ Tubuh Rajungan (Portunus pelagicus, Linn)

Blue Swimming crab ( Portunus pelagicus ) is one of important fishery in Indonesia that captured nearshore on the bottom of the sea. There has been a significant water contamination on the Jakarta bay and the fishery are reported to be effected. Many heavy metals and other contaminants are introduced into the waters, sediments, and fishery that living in the bay. Heavy metals such as Pb, Cd, Hg and As are the most lethal contaminants and found in Jakarta Bay. This study aims to determine the effect of heavy metals contaminants to the blue swimming crab morphometric, body organs and population structure of blue swimming crabs in Jakarta bay, which compared to the study in healthier environment in Madura island. The results of this study showed that 1) The morphometric parameter of blue swimming crab population in Jakarta and Madura are significantly different. 2) The internal organ of the blue swimming crab (hepatopancreas, gonad and gill) in Jakarta bay are also significantly different than in Madura. The histological analysis are confirmed some abnormal indication of the internal body of the blue swimming crab in Jakarta bay.3) Some population parameters of the blue swimming crab in jakarta bay are significantly different than in Madura island. The fishery structure in Jakarta bay showed the size of first maturity of the crabs is relatively smaller than in Madura and other area of Inodonesia. The fishery mangament based on spatial area management is recommended to apply in different area of Indonesia. Keywords: heavy metal contamination, blue swimming crab

Bifurcation analysis of anti-phase oscillations and synchrony in the tadpole central pattern generator

Recent experimental findings in the laboratory of Wen-Chang Li (St. Andrews University, UK) demonstrate that the same neural Central Pattern Generator (CPG) within the hindbrain/spinal cord of the Xenopus tadpole can produce both reliable anti-phase oscillations between the left and right sides of the body (swimming) and long bouts of in-phase synchronous activity. The key element of the CPG circuit includes a pair of neurons on each side of the body at about the same position: an excitatory descending interneuron (dIN) and an inhibitory commissural interneuron (cIN). A simplified description of the CPG activity in swimming regime follows from experimental facts: dIN spiking on one side leads to excitation of the cIN on the same side, which inhibits the dIN on the opposite side causing a spike due to post-inhibitory rebound (PIR). Similarly, experiments suggest that synchrony appears as a result of simultaneous firing of dINs on both sides which leads to simultaneous firing of cINs on both sides, followed by inhibition of dINs (on opposite sides) and a new cycle of simultaneous dIN firing due to PIR. To study these exciting experimental findings we use biologically realistic anatomical and functional computational models [1-3]. The tadpole swimming model represents a 1.5 mm section of tadpole spinal cord with ~ 1,500 neurons, interconnected by ~ 85,000 synapses. Neuron dynamics are simulated according to a conductance based model of the Hodgkin-Huxley type. Additionally, gap junctions between dINs within 100µm of each other in the rostro-caudal direction are included. From studying the dynamics of this model and bifurcation analysis of the key element of the CPG circuit, we conclude: 1. There are two limit cycles in the phase space of the model: an anti-phase limit cycle with period T which corresponds to swimming activity, and an in-phase limit cycle with period T/2 which corresponds to synchrony (see Figure ​Figure11). Figure 1 Phase portraits of the system during anti-phase (green) and in-phase (blue) activity. Horizontal and vertical axes correspond to membrane potentials of dINs at similar positions on the left and right body side respectively. 2. The anti-phase (swimming) cycle is stable and robust with a large basin of attraction. The in-phase (synchrony) cycle can be initiated from swimming regime by mid-cycle stimulation of dIN neurons, but is generally unstable or has a very small basin of attraction. 3. The in-phase cycle is near a fold of limit cycles bifurcation. For a minority of generated connections the stable in-phase limit cycle exists. However, for most connections this stable cycle does not exist, although its “ghost” is still visible: after several synchronous cycles the system returns to swimming oscillations. 4. The stability of synchrony is extremely sensitive to the synaptic/conductance delays between dINs and cINs, with longer delays stabilizing synchrony. 5. It is unclear whether synchrony has a functional purpose. If it does, we hypothesize that in this early developmental stage the system may be near to the critical bifurcation point in order to provide flexibility in locomotion control. As the tadpole develops, longer synaptic delays may act to stabilize the synchronous firing pattern.

Shape variation in a benthic stream fish across flow regimes

Evolution of fish body shapes in flowing and non-flowing waters have been examined for several species. Flowing water can select for fish body shapes that increase steady swimming efficiency, whereas non-flowing water can favor shapes that increase unsteady swimming efficiency. Benthic stream fishes often use areas near the substrate that exhibit reduced or turbulent flow, thus it is unclear which swimming forms would be favored in such environments, and how shape might change across flow regimes. To test the relationship between fish body shape and flow regime in a benthic stream fish, we used geometric morphometric techniques to characterize lateral body shape in mountain sucker (Catostomus platyrhynchus) across flow rates, using stream gradient as an indicator of stream flow. Mountain suckers from low-flow environments were more streamlined, consistent with steady swimming body shapes, whereas mountain suckers from high flows had deeper bodies, consistent with unsteady swimming body shapes. In addition, smaller individuals tended to have more robust body shapes. These patterns are opposite to those predicted for stream fishes in the mid-water column. The benthic stream environment represents a distinct selective environment for fish shape that does not appear to conform to the simple dichotomy of flowing versus non-flowing water.

Robot fish with a novel biomimetic wire-driven flapping propulsor

This paper presents a robot fish actuated by a novel biomimetic wire-driven flapping propulsor. The propulsor is composed by a flexible backbone and two sets of controlling wires. The backbone has 13 vertebras. They are articulated by cylindrical joints and an elastic fin plate. These vertebras are divided into two groups. Each group is controlled by one pair of wires and one actuator. By controlling the two sets of wires, the propulsor can generate oscillatory motion (C-Motion) and undulatory motion (S-Motion). The motions well resemble the fish swimming body curve. A prototype is developed and four swimming tests were conducted, i.e. ‘Big-C-Motion’ forward, ‘Small-C-Motion’ forward, ‘S-Motion’ forward and turning. Only two actuators are used in this prototype. Experimental results validated the effectiveness of the wire-driven design. Results show that the robot fish’s swimming performance is satisfactory. The forward swimming speed is influenced by the flapping amplitudes, waving frequency, the phase lag of the two segments and the swimming stability. In the experiments, the maximum cruise speed is 300.75 mm/s (0.608 BL/s) (BL/s is Body Length/s) in ‘C-Motion’ and 333.33 mm/s (0.673 BL/s) in ‘S-Motion’. The turning radius of the robot fish is around 0.7 BL, and the truning speed is 51.4 °/s.