Electromechanical dynamics and optimization of pectoral fin-based ionic polymer-metal composite underwater propulsor

Ionic polymer-metal composites are soft artificial muscle-like bending actuators, which can work efficiently in wet environments such as water. Therefore, there is significant motivation for research on the development and design analysis of ionic polymer-metal composite based biomimetic underwater propulsion systems. Among aquatic animals, fishes are efficient swimmers with advantages such as high maneuverability, high cruising speed, noiseless propulsion, and efficient stabilization. Fish swimming mechanisms provide biomimetic inspiration for underwater propulsor design. Fish locomotion can be broadly classified into body and/or caudal fin propulsion and median and/or paired pectoral fin propulsion. In this article, the paired pectoral fin-based oscillatory propulsion using ionic polymer-metal composite for aquatic propulsor applications is studied. Beam theory and the concept of hydrodynamic function are used to describe the interaction between the beam and water. Furthermore, a quasi-steady blade element model that accounts for unsteady phenomena such as added mass effects, dynamic stall, and the cumulative Wagner effect is used to obtain hydrodynamic performance of the ionic polymer-metal composite propulsor. Dynamic characteristics of ionic polymer-metal composite fin are analyzed using numerical simulations. It is shown that the use of optimization methods can lead to significant improvement in performance of the ionic polymer-metal composite fin.

Fish inspired biomimetic ionic polymer metal composite pectoral fins using labriform propulsion

Ionic polymer metal composites (IPMC) are a new class of smart materials that have attractive characteristics such as muscle like softness, low voltage and power consumption, and good performance in aqueous environments. Thus, IPMC’s provide promising application for biomimetic fish like propulsion systems. In this paper, we design and analyze IPMC underwater propulsor inspired from swimming of Labriform fishes. Different fish species in nature are source of inspiration for different biomimetic flapping IPMC fin design. Here, three fish species with high performance flapping pectoral fin locomotion is chosen and performance analysis of each fin design is done to discover the better configurations for engineering applications. In order to describe the behavior of an active IPMC fin actuator in water, a complex hydrodynamic function is used and structural model of the IPMC fin is obtained by modifying the classical dynamic equation for a slender beam. A quasi-steady blade element model that accounts for unsteady phenomena such as added mass effects, dynamic stall, and the cumulative Wagner effect is used to estimate the hydrodynamic performance of the flapping rectangular shape fin. Dynamic characteristics of IPMC actuated flapping fins having the same size as the actual fins of three different fish species, Gomphosus varius, Scarus frenatus and Sthethojulis trilineata, are analyzed with numerical simulations. Finally, a comparative study is performed to analyze the performance of three different biomimetic IPMC flapping pectoral fins.

Bioconvection in an anisotropic scattering suspension of phototactic algae

Phototaxis is a directed swimming response dependent upon the light intensity sensed by microorganisms. Positive phototaxis denotes motion directed towards the source of light and negative phototaxis is motion directed away from it. In this paper, we investigate the onset of bioconvection in a suspension of anisotropic scattering phototactic algae illuminated by collimated radiation at the top. The basic state of the system is defined by the zero fluid flow and the up and down swimming, caused by the positive and negative phototaxis, is balanced by the diffusion. A comprehensive numerical study of the linear stability is presented with particular emphasis on the forward scattering effect. The onset of bioconvection occurs either via a stationary mode or an oscillatory mode. The transition from a stationary mode to an oscillatory mode or vice versa has been observed as the anisotropic coefficient is varied for certain parameter values. (C) 2012 Elsevier Masson SAS. All rights reserved.

Penetrative phototactic bioconvection in an isotropic scattering suspension

Phototaxis is a directed swimming response dependent upon the light intensity sensed by micro-organisms. Positive (negative) phototaxis denotes the motion directed towards (away from) the source of light. Using the phototaxis model of Ghorai, Panda, and Hill ''Bioconvection in a suspension of isotropically scattering phototactic algae,'' Phys. Fluids 22, 071901 (2010)], we investigate two-dimensional phototactic bioconvection in an absorbing and isotropic scattering suspension in the nonlinear regime. The suspension is confined by a rigid bottom boundary, and stress-free top and lateral boundaries. The governing equations for phototactic bioconvection consist of Navier-Stokes equations for an incompressible fluid coupled with a conservation equation for micro-organisms and the radiative transfer equation for light transport. The governing system is solved efficiently using a semi-implicit second-order accurate conservative finite-difference method. The radiative transfer equation is solved by the finite volume method using a suitable step scheme. The resulting bioconvective patterns differ qualitatively from those found by Ghorai and Hill ''Penetrative phototactic bioconvection,'' Phys. Fluids 17, 074101 (2005)] at a higher critical wavelength due to the effects of scattering. The solutions show transition from steady state to periodic oscillations as the governing parameters are varied. Also, we notice the accumulation of micro-organisms in two horizontal layers at two different depths via their mean swimming orientation profile for some governing parameters at a higher scattering albedo. (C) 2013 AIP Publishing LLC.

Fish Inspired Biomimetic Ionic Polymer-Metal Composite Pectoral Fins Using Labriform Propulsion

In this article, we analyze and design ionic polymer metal composite (IPMC) underwater propulsors inspired from swimming of labriform fishes. The structural model of the IPMC fin accounts for the electromechanical dynamics of the bean in water. A quasi steady blade element model that accounts for unsteady phenomena, such as added mass effects, dynamic stall, and cumulativeWagner effect is used to estimate the hydrodynamic performance. Dynamic characteristics of IPMC actuated flapping fins having the same size as the actual fins of three different fish species, Gomphosus varius, Scarus frenatus, and Sthethojulis trilineata, are analyzed using numerical simulations.

New tools for self-organised pattern formation

Position-dependent gene expression is a critical aspect of the development and behaviour of multicellular organisms. It requires a complex series of interactions to occur between different cell types in addition to intracellular signalling cascades. We used Escherichia coli to study the properties of an artificial signalling system at the interface between two expanding cell populations. We genetically engineered one population to produce a diffusible acyl-homoserine lactone (AHL) signal, and another population to respond to it. Our experiments demonstrate how such a signal can be used to reproducibly generate simple visible patterns with high accuracy in swimming agar. The producing and responding cassettes of two such signalling systems can be linked to produce a symmetric interface for bidirectional communication that can be used to visualise molecular logic. Intracellular feedback between these two cassettes would then create a framework for self-organised patterning of higher complexity. Adapting the experiments of Basu et al. (Basu et al., 2005) using cell motility, rather than a differential response to AHL concentrations as a way to define zones of response, we noted how the interaction of sender and receiver cell populations on a swimming plate could lead to complex pattern formation. Equipping highly motile strains such as E. coli MC1000 with AHL-mediated auto-inducing systems based on Vibrio fischeri luxI/luxR and Pseudomonas aeruginosa lasI/lasR cassettes would allow the amplification of a response to an AHL signal and its propagation. We designed and synthesised codon-optimised auto-inducing luxI/R and lasI/R cassettes as optimal gene expression is crucial for the generation of robust patterns. We still have to complete and test the entire genetic circuitry, although by modelling the system we were able to demonstrate its feasibility. © 2007 The Institution of Engineering and Technology.

Detecting fish aggregations from reef habitats mapped with high resolution side scan sonar imagery

As part of a multibeam and side scan sonar (SSS) benthic survey of the Marine Conservation District (MCD) south of St. Thomas, USVI and the seasonal closed areas in St. Croix—Lang Bank (LB) for red hind (Epinephelus guttatus) and the Mutton Snapper (MS) (Lutjanus analis) area—we extracted signals from water column targets that represent individual and aggregated fish over various benthic habitats encountered in the SSS imagery. The survey covered a total of 18 km2 throughout the federal jurisdiction fishery management areas. The complementary set of 28 habitat classification digital maps covered a total of 5,462.3 ha; MCDW (West) accounted for 45% of that area, and MCDE (East) 26%, LB 17%, and MS the remaining 13%. With the exception of MS, corals and gorgonians on consolidated habitats were significantly more abundant than submerged aquatic vegetation (SAV) on unconsolidated sediments or unconsolidated sediments. Continuous coral habitat was the most abundant consolidated habitat for both MCDW and MCDE (41% and 43% respectively). Consolidated habitats in LB and MS predominantly consisted of gorgonian plain habitat with 95% and 83% respectively. Coral limestone habitat was more abundant than coral patch habitat; it was found near the shelf break in MS, MCDW, and MCDE. Coral limestone and coral patch habitats only covered LB minimally. The high spatial resolution (0.15 m) of the acquired imagery allowed the detection of differing fish aggregation (FA) types. The largest FA densities were located at MCDW and MCDE over coral communities that occupy up to 70% of the bottom cover. Counts of unidentified swimming objects (USOs), likely representing individual fish, were similar among locations and occurred primarily over sand and shelf edge areas. Fish aggregation school sizes were significantly smaller at MS than the other three locations (MCDW, MCDE, and LB). This study shows the advantages of utilizing SSS in determining fish distributions and density.

Analysis of fish diversion efficiency and survivorship in the fish return system at San Onofre Nuclear Generating Station

This study examined the efficiency of fish diversion and survivorship of diverted fishes in the San Onofre Nuclear Generating Station Fish Return System in 1984 and 1985. Generally, fishes were diverted back to the ocean with high frequency, particularly in 1984. Most species were diverted at rates of 80% or more. Over 90% of the most abundant species, Engraulis mordax, were diverted. The system worked particularly well for strong-swimming forms such as Paralobrax clothratus, Atherinopsis californiensis, and Xenistius californiensis, and did not appreciably divert weaker-swimming species such as Porichthys notatus, Heterostichus rostratus, and Syngnathus sp. Return rates of some species were not as high in 1985 as in 1984. Individuals of most tested species survived both transit through the fish return system and 96 hours in a holding net. Some species, such as E. mordox, X. californiensis, and Umbrina roncador, experienced tittle or no mortality. Survivorship of Seriphus politus was highly variable and no Anchoa delicatissima survived. (PDF file contains 22 pages.)

An egg production method for estimating spawning biomass of pelagic fish: Application to the northern anchovy, Engraulis mordax

Fishery scientists engaged in estimating the size of free-swimming populations have never had a technique available to them whereby all the parameters could be estimated from a resource survey and where no parameter values need to be assumed. Recognizing the need for a technique of this kind, the staff of the Coastal Fisheries Resources Division of the Southwest Fisheries Center (SWFC) devised an egg production method for anchovy biomass assessment. Previously, anchovy biomass was estimated by approximate methods derived from a long-time series and anchovy larval abundance, which required about 5 ma of shiptime each year to integrate the area under a seasonal spawning curve. One major assumption used in the larval abundance census method is that there is constant proportionality between larval numbers and spawning biomass. This has now proved to be erroneous. (PDF file contains 105 pages.)

Horizontale Trennblätter in Trawls zur Verringerung von Discards in der Ostsee

A primary objective of the Common Fishery Policy of the European Union is the reduction of discards and unwanted by-catches in the fishery. In principle this could be achieved if the catching methods were optimised for this. Still high numbers of undersized flatfish are caught in the bottom trawls. Although EU regulations make the use of the BACOMA codend mandatory in the Baltic Sea cod areable to escape through square mesh escape window of the BACOMA net the whereas flatfish still remain in the cod-end. Gear experiments have been carried out with the aim to better separate cod from the flatfish fraction already when entering the rear belly, making use of the natural behaviour of the fish, i. e. the preferred swimming distance from the bottom of the net in the funnel. As cod have a natural tendency to keep a relativly great distance from the bottom, flatfish tend to stay close to it. It was attempted to separate both fractions by splitting the funnel into an upper and lower part with a horizontal panel. This wastested for two different nets, a cod trawl to separate cod from flatfish, and an eel-trawl to separate cod and flatfish from eel. Cod and flatfish separation is best at a panel distance of 50 cm from the bottom. Thus, 74 % of the cod were found in the upper panel, whereas 75 % of the flounder were in the lower section. A separation of eel from cod was however not possible, since eel tend to rise to the upper part of the net, together with cod.

Acute toxicities of Basudine and Gammalin 20 to Aphyosemin gairdneri

Effects of Basudine and Gammalin 20 on the fingerlings of Aphyosemin gairdneri were investigated using static bioassays and continuous aeration over a period of 48 hours. The 48 hours LC sub(50) of the exposed fish to Basudine and Gammalin 20 were determined to be 194.99 mu g dm super(3) and 95.50 mu g dm super(3) respectively. Gammalin 20 was more toxic than Basudine. The behavioural responses observed include agitation, erratic swimming, loss of equilibrium, period of quiescence and death. It is concluded that repeated applications of these herbicides should be avoided before stocking ponds with fish

Acute toxicity of Gammalin 20 to Chrysichthys nigrodigitatus (Lacepede)

The impact of acute exposure of Gammalin 20 (an organochlorine pesticide) was investigated in a static bioassay test over a 96-(4-day) period on the fingerlings of Chrysichthys nigrodigitatus (lacepede). The 96-hLC sub(50) of Gammalin 20 was determined as 2.31 Ug/l with lower and upper limits of toxicities as 2.10 and 4.44 Ug/l respectively. At higher concentrations, the colour of the exposed fish became darker, opercular movement slowed down while pigmentation pattern increased and respiratory distress was observed, erratic swimming, tonic convulsion and no response to gentle prodding, and finally death. The implications of these results were discussed with a suggestion of the total ban on the use of Gammalin 20 in capture fisheries due to its harmful and persistence nature in the aquatic environment

A dynamical systems analysis of vortex pinch-off

Vortex rings constitute the main structure in the wakes of a wide class of swimming and flying animals, as well as in cardiac flows and in the jets generated by some moss and fungi. However, there is a physical limit, determined by an energy maximization principle called the Kelvin-Benjamin principle, to the size that axisymmetric vortex rings can achieve. The existence of this limit is known to lead to the separation of a growing vortex ring from the shear layer feeding it, a process known as `vortex pinch-off', and characterized by the dimensionless vortex formation number. The goal of this thesis is to improve our understanding of vortex pinch-off as it relates to biological propulsion, and to provide future researchers with tools to assist in identifying and predicting pinch-off in biological flows.

To this end, we introduce a method for identifying pinch-off in starting jets using the Lagrangian coherent structures in the flow, and apply this criterion to an experimentally generated starting jet. Since most naturally occurring vortex rings are not circular, we extend the definition of the vortex formation number to include non-axisymmetric vortex rings, and find that the formation number for moderately non-axisymmetric vortices is similar to that of circular vortex rings. This suggests that naturally occurring vortex rings may be modeled as axisymmetric vortex rings. Therefore, we consider the perturbation response of the Norbury family of axisymmetric vortex rings. This family is chosen to model vortex rings of increasing thickness and circulation, and their response to prolate shape perturbations is simulated using contour dynamics. Finally, the response of more realistic models for vortex rings, constructed from experimental data using nested contours, to perturbations which resemble those encountered by forming vortices more closely, is simulated using contour dynamics. In both families of models, a change in response analogous to pinch-off is found as members of the family with progressively thicker cores are considered. We posit that this analogy may be exploited to understand and predict pinch-off in complex biological flows, where current methods are not applicable in practice, and criteria based on the properties of vortex rings alone are necessary.

Studies of the effects from extracts from two local plants (Tephrosia vogelii and Parkia clappertoniana) on Clarias gariepinus (Tengels)

Studies were carried out using 96hr static toxicity bioassay to determine the effect of lethal concentrations of extracts from two local plants Tephrosia vogelii and Parkia clappertoniana which are known fish poison, on a species of mud fish. Clarias gariepinus Phytochemical analysis of the plant extracts was done and the extract from T. vogelii was found to contain alkaloids, tannins and flavonoids, while the extract from P. clappertoniana was formed to contain alkaloids tannins and saponins. Experimental fish were exposed to test water separately polluted by varying concentrations of extraction of both plant species ranging from 0.50mgl super(-1), 1.50mgl super(-1), 2.50mgl super(-1), 3.0mgl super(-1), 5.00mgl super(-1), 10.00mgl super(-1) in the case of T. vogelii and 5.00mgl super(-1), 7.50mgl super(-1), 10.00mgl super(-1), 15.00mgl super(-1), 20.00mgl super(-1) and 30.00mgl super(-1) in the case of P. clappertaniana. Behavioural hispathological and heamatological examinations were made. Both plant extracts were found to have lethal effects at the higher concentrations, affecting the gills and the central nervous system as well as having a depressive effect on the total count and increasing platelet and white blood cell count. Symptoms of toxicosis observed include, initial inactivation agitated swimming, tumbling movement air gulping, increased opercular beat and period of quiescence/knockdown before death. Marked differences were also observed in the hematological and histopathological analysis of poisoned fish. Lower concentrations of the extracts had sub lethal effects on the fish, which manifested as zigzag movement air gulping increased opercular movement etc. None of these effects were observed in the control experiment

Toxicity of linear alkylbenene sulphonate (LAS) detergent, to Clarias gariepinus fingerlings

The acute toxicity of Linear Alkylbenzene Sulphonate (LAS) detergent to Clarias gariepinus fingerlings was investigated using static bioassays and continous aeration over a period of 96h. The 96h LC sub(50) was determined as 24.00mgL super(-1). During the exposure period, the test fish exhibited several behavioural changes before death such as restlessness, rapid swimming, loss of balance, respiratory distress and haemorrhaging of gill filaments amongst others. Opercula ventilation rate as well as visual examination of dead fish indicates lethal effects of the detergent on the fish. Water quality examination showed increase in pH from 6.55 to the alkaline, death point of 10.55. There was also a remarkabel rise of alkalinity from 20.00mgL super(-1) to 52.50mgL super(-1)