Large Fin Research Articles

Kinematics and hydrodynamic performance of zebrafish C-type maneuvers: A comparison of two- and three-dimensional simulations

Two-dimensional (2D) and three-dimensional (3D) numerical models are commonly employed to investigate the kinematic and hydrodynamic characteristics of fish maneuvers. In this study, we captured the posture characteristics of zebrafish during C-type maneuvers using high-speed photography and constructed a midline curvature model via the tandem principal characteristics method, which exhibited a “double peak and single valley” structure. Based on this curvature model, self-propelled simulations were conducted using the immersed boundary method with adaptive mesh refinement. The results showed that, under identical deformation conditions, the 2D simulation exhibited a 16.8% higher centroid velocity, 6.1% greater overall angular velocity, and an 11.9% larger turning angle compared to the 3D simulation. This discrepancy is primarily due to the 2D model’s inability to accurately represent the fish body’s mass distribution and force characteristics, resulting in artificially elevated performance. Nevertheless, 2D simulations remain applicable for studying the propulsion performance of fish with elongated cross-sections and large fin areas. Comparison between the simulated and real motion performance reveals that, under the self-propelled computational model, both 2D and 3D numerical simulations consistently capture the qualitative motion patterns. The quantitative results also reflect the actual swimming performance of the fish within an acceptable margin of error.

Fluid–Structure Interaction Analysis of Manta-Bots with Self-Induced Vertical Undulations during Fin-Based Locomotion

Driven by the demands of ocean exploration, an increasing number of manta ray-inspired robots have been designed and manufactured, primarily utilizing flexible skeletons combined with motor-driven mechanisms. However, the mechanical analysis of these designs remains underdeveloped, often relying on simplistic imitation of biological prototypes and typically neglecting the vertical motion induced by pectoral fin flapping. This paper presents a fluid–structure interaction analysis framework that couples rigid body motion with elastic deformation using flexible multibody dynamics and the vortex particle method. An implicit iterative algorithm with Aitken relaxation is employed to address added-mass instability, and the framework has been validated against experimental data. An analysis of a representative manta-bot model shows that self-induced vertical undulations reduce the thrust coefficient by approximately 40% compared to fixed vertical degrees of freedom, while slightly improving overall propulsive efficiency. The study also highlights the critical role of mass distribution in manta-bots, noting that excessive focus on complex pectoral fin movements and large fin mass can significantly reduce thrust by increasing vertical displacement, ultimately proving counterproductive.

A NOVEL SPECIES OF MYXOBOLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE GILL OF GREEN SUNFISH, LEPOMIS CYANELLUS (PERCIFORMES: CENTRARCHIDAE), FROM THE BLACK RIVER OF NORTHEASTERN ARKANSAS.

During March 2023, 7 green sunfish (Lepomis cyanellus) and 2 bluegill (Lepomis macrochirus) were collected from the Black River (White River drainage) in Lawrence County, Arkansas. In addition, during March 2023 and again in May-June 2023, 13 L. cyanellus and 6 L. macrochirus were taken from Butcherknife and Big Fork creeks (Ouachita River drainage), Polk County, Arkansas, 9 L. cyanellus were collected from the Caddo River, Montgomery County, Arkansas, and 5 green sunfish were taken from Clear Creek at Savoy, Washington County, Arkansas. All fish had their gill, gallbladder, fins, integument, musculature, and other major organs examined for myxozoans. The gill of 1 of 34 (3%) L. cyanellus was infected with a new myxozoan, Myxobolus fergusoni n. sp. Qualitative and quantitative morphological data were obtained from fresh myxospores, and molecular data consisted of a 1,933-base-pair sequence of the partial small subunit (SSU) ribosomal RNA (rRNA) gene. Phylogenetic analysis grouped M. fergusoni n. sp. with other centrarchid-infecting myxobolids from North America and placed this cluster in a larger clade comprising myxozoans that infect North American and European esocids, a North American aphredoderid, European percids, and a gasterosteid from Japan. Myxobolus fergusoni n. sp. infects the gill arches of L. cyanellus, similar to Myxobolus cartilaginis (Hoffman, Putz, and Dunbar, 1965), which was described from head cartilage, gill arches, and large fin rays of L. cyanellus. Another is Myxobolus mesentericusKudo, 1920, which was described from the viscera of green sunfish. A large polysporic plasmodium filled with myxospores was present in a basifilamental location associated with multiple gill filaments at their junction with the gill arch. The intact plasmodium replaced connective tissue within the arch but elicited only mild proliferation of overlying epithelium and a minimal host inflammatory response. This is the third time a myxozoan has been described from L. cyanellus, as well as being the first time it has been described from an Arkansas specimen.

Finotypic plasticity: Predator-induced plasticity in fin size, darkness and display behaviour in a teleost fish.

Fish fins are remarkable devices of propulsion. Fin morphology is intimately linked to locomotor performance, and hence to behaviours that influence fitness, such as foraging and predator avoidance. This foreshadows a connection between fin morphology and variation in predation risk. Yet, whether prey can adjust fin morphology according to changes in perceived risk within their lifetime (a.k.a. predator-induced plasticity) remains elusive. Here, we quantify the structural size of five focal fins in crucian carp (Carassius carassius) following controlled manipulations to perceived predation risk (presence/absence of pike Esox lucius). We also assess if crucian carp respond to increased predation risk by shifts in dorsal fin colouration, and test for differences in how fish actively use their dorsal fins by quantifying the area of the fin displayed in behavioural trials. We find that crucian carp show phenotypic plasticity with regards to fin size as predator-exposed fish consistently have larger fins. Individuals exposed to perceived predation risk also increased dorsal fin darkness and actively displayed a larger area of the fin to potential predators. Our results thus provide compelling evidence for predator-induced fin enlargement, which should result in enhanced escape swimming performance. Moreover, fin-size plasticity may evolve synergistically with fin colouration and display behaviour, and we suggest that the adaptive value of this synergy is to enhance the silhouette of deep-bodied and hard-to-capture prey to deter gape-limited predators prior to attack. Together, our results provide new perspectives on the role of predation risk in development and evolution of fins.

Performance optimization of adsorption hydrogen storage system via computation fluid dynamics and machine learning

Adsorption hydrogen storage paves an alternative way for reliable hydrogen storage. Here, impacts of dimensionless fin geometry configurations of the fin-tube metal hydride bed on the hydrogen storage performance are systematically investigated. Results show employing fins can strengthen the heat and mass transfer characteristics in the adsorbent bed and shorten the adsorption duration, especially at large fin numbers. Larger dimensionless fin thickness, height and width can lower the average bed temperature, which contributes to the adsorption kinetics and hydrogen fraction. At a small adsorption duration, larger dimensionless fin thickness, height and width improve the hydrogen storage amount due to obviously augmented hydrogen fraction. At a larger adsorption duration, there exist optimal dimensionless fin thickness, height and width leading to the maximum hydrogen storage amount originating from the compromise between the hydrogen fraction and adsorbent filled. Based on machine learning, the relationships between dimensionless fin geometry parameters and hydrogen storage amount have been obtained, and the optimal adsorption duration depended dimensionless fin configurations are obtained based on genetic algorithm. At a moderate adsorption duration, the optimized finned bed can significantly enhance the hydrogen storage amount. At the adsorption duration of 400 s, the hydrogen storage amount is augmented by 12.8%.

Pool boiling performance for GaldenR HT 55 subject to smooth, pin fin, and sintered pin fin heat sink

The dielectric fluid of GaldenR HT 55 (Perfluoropolyether) is regarded as a potential candidate for two-phase immersion cooling since its boiling point at 1 atm is 55 °C which is quite suitable for electronics cooling. The fluid is of special interest since the main vender of dielectric fluid will no longer produce FGAS after 2024. However, very rare nucleate boiling performance data for HT55 were reported in the literature. The objective of this study aims to provide nucleate boiling performance data for various heat sinks applicable for nucleate boiling. The test samples include a smooth reference surface (#1), 2 pin fins (the pin diameters are 1 mm (#2) and 2 mm (#3), and 3 pin fin with various sintered coatings (powder size: 150–200 μm (#4), 200–250 μm (#5), and 250–350 μm (#6)). Heat flux spans from 80 to 600 kW/m2. HTC for small pin fin (#2) is marginally higher than that of smooth surface, and large pin fin (#3) shows about 40 % enhancement compared to smooth surface at 140 kW/m2. HTCs for sintered pin fins are much higher than those of pin fin or smooth surface with approximately 90–95 % enhancement relative to the smooth surface at low heat flux. The visual observations indicate that sample #6 yields the largest bubble departure diameter and departure frequency. Yet bubble generations are especially pronounced on top of the pin fin. The CHF of the tested surfaces are following the sequence: #5 > #6 > #4 > #3 > #2 > #1. The sample #5 contains a CHF over 600 kW/m2 which is about four times higher than that of the smooth surface.

Analysis fin field-effect transistor design with high-k insulators

In this article, we integrate a Fin Field Effect Transistor with high-k insulators to investigate the optimal design for chemical field effect transistors in order to give higher inductance (resulting in a higher transmission relationship), improved amplitude, and outcome-based substance. pH sensing was utilised to test the design. We investigated the responsiveness and linearity of silicon dioxide, oxide, and hafnium oxide as pH-sensing electromagnetic materials, as well as their chemical resistance in various acids. The device’s huge component ratio and fin shape allow for high currents and a more dependable planar conducting channel than conventional silicon nanowires. The hafnium oxide Fin Field Effect Transistor architecture delivered the greatest results, with the most linear features of generation and turnover and a broader dynamic range. The chemical stability of hafnium oxide was also the best. As a result, we believe the large component ratio Fin Field Effect Transistors/high-k dielectric combination can provide the optimal process fairness for Field-Effect Transistor-based sensors. The authors propose a novel seamless embedded induction approximation with a quaternary resonator. Only one deleterious modified divergent voltage current conveyor, one of the suggested quaternary synthesisers, uses a Z input, a rectifier, and two crossed capacitive. In the intended unidirectional isolated circuit emulator, just one customised split electrical output feeder with a sole Z electrode, two switches, and the first neutral capacitor are used. The suggested seamless rooted circuit simulation just requires a specific passive constituent compatibility criterion. In addition, the suggested lossless grounded inductor simulator yields a ring filter application. To illustrate the performance of all the circuits, a variety of models using the LTSPICE software, the cadence virtuoso 7nm parameter, and data analyses were performed.

Numerical Investigation of Fin Shape Optimization and Entropy of Magnetohydrodynamics Natural Convection Nanofluid Flow in a Cavity

The purpose of the investigation is to analyze the effect of fin length and position in terms of rotational angle on heat transmission and entropy generation. Different parameters such as Prandtl numbers, Hartmann numbers, Rayleigh numbers, and particle volume fractions are used to analyze nanofluid laminar flow behavior and temperature distribution. The fin has a significant impact on both the isotherm and the streamlines. Findings revealed that increasing the rotational angle of a spinning heat exchanger might result in more consistent temperature distribution along isotherms; larger fins, on the other hand, frequently provide greater heat dissipation due to increased surface area. Furthermore, when Rayleigh numbers increase, so does the temperature distribution between the fins and the surrounding fluid. The presence of a magnetic field affects fluid dynamics and contributes to the generation of entropy. Higher Prandtl numbers can result in the enhancement heat transfer phenomena and the generation of entropy.

Effects of strut cover and lower vertical fin in podded propulsion units on ship maneuverability

To investigate the effects of a strut cover and lower vertical fin in podded propulsion units (POD units) on the maneuverability of a POD-driven ship, free-running model tests (turning test, spiral/revers spiral test, and zig-zag maneuver test) were conducted for three different profiles of the POD units: only a vertical strut without the strut cover or fin (F0), smaller strut cover and smaller fin (FS), and larger strut cover and larger fin (FL). The profile area increases in the order of F0, FS, and FL. The tests were conducted using two propeller positions: one with a propeller equipped in front of the POD units (PULL position) and another with the propeller equipped behind the POD units (PUSH position). The steady turning performance at a steering angle of 35° in the PULL position deteriorated in the order of F0, FS, and FL. In contrast, in the case of the PUSH position, the turning performance improved in the order of F0, FS, and FL. Thus, the PULL and PUSH positions demonstrated different tendencies. The non-dimensional steady yaw rate exceeded 1.0 in all cases, which indicates that the present ship has an excellent turning performance. Furthermore, captive model tests (the POD steering force test in straight towing, oblique towing test, and circular motion test) were conducted to determine the effects of the strut cover and lower vertical fin on the lateral force and yaw moment acting on the ship model. It was found that the large strut cover and fin increase the steering force and improves the course stability of the ship in both the PULL and PUSH positions.

Constructal design of vertical multiscale triangular fins in natural convection

AbstractConstructal design of vertical multiscale triangular fins in natural convection is investigated in this paper. The design consists of two parts. The first part is for single‐scale triangular fins. The objective in the first design is to reach to the highest heat transfer density from the fins for three fin angles (15°, 30°, and 45°). The single‐scale fins are placed in a horizontal array and considered as isothermal fins. The degrees of freedom are the fin angle, and the fin‐to‐fin spacing. The constraint is the fin height. The second part is for multiscale fins where small fins are placed between the large fins which are optimized in the first part. In the second part, the angles of the large and small scales fins are kept constant at (15°). The optimal fin‐to‐fin spacing which is obtained in the first part is considered a constraint in the second part. The Rayleigh numbers in this design are (Ra = 103, 104, and 105). The two‐dimensional mass, momentum, and energy equations for natural convection are solved with the finite volume method. The results show that there is a benefit of placing the small‐scale fins where the percentage increase in the heat transfer density is (10.22%) at (Ra = 103), and (50.6%) at (Ra = 105) due to existence of the small fins between the large fins.

Melting process of Carreau non-Newtonian nano-phase change material inside cylindrical energy storage system: Effect of thermal fins

Melting of a non-Newtonian phase-change material in a finned porous vertical cylinder was numerically studied. The governing equations and corresponding boundary conditions were derived by the enthalpy–porosity technique in cylindrical coordinates. The equations were then non-dimensionalized and solved by the finite element method. The grid independence of the solution was evaluated, and the fluid dynamics code was validated by comparison with accredited numerical and experimental studies. The results were discussed regarding the number and size of thermal fins and the aspect ratio parameter regarding to the melting volume fraction, the total energy stored, the average Nusselt number, the average velocity, the contour of isotherms, and streamlines. The results showed that increasing the number of the fins from 1 to 5 and using larger fins instead of shorter ones positively affected the time required for completing the melting process by 16% and 20%, respectively. It is worth noting that a storage system with a higher aspect ratio (AR = 2) than a lower one (AR = 0.5) shortens the melting process by about 80%. The maximum value of the total energy stored remains constant with any change in the number and size of the fins; however, it is diminished by reducing the aspect ratio.

A lionfish-inspired predation strategy in planar structured environments *

This paper investigates a pursuit-evasion game with a single pursuer and evader in a bounded environment, inspired by observations of predation attempts by lionfish (Pterois sp.). The pursuer tracks the evader with a pure pursuit strategy while using an additional bioinspired tactic to trap the evader, i.e. minimize the evader’s escape routes. Specifically, the pursuer employs symmetric appendages inspired by the large pectoral fins of lionfish, but this expansion increases its drag and therefore its work to capture the evader. The evader employs a bioinspired randomly-directed escape strategy to avoid capture and collisions with the boundary. Here we investigate the trade-off between minimizing the work to capture the evader and minimizing the evader’s escape routes. By using the pursuer’s expected work to capture as a cost function, we determine when the pursuer should expand its appendages as a function of the relative distance to the evader and the evader’s proximity to the boundary. Visualizing the pursuer’s expected work to capture everywhere in the bounded domain, yields additional insights about optimal pursuit trajectories and illustrates the role of the boundary in predator-prey interactions.

Numerical study of three-dimensional microchannel using the Constructal Law

In this work it was performed a numerical study about the design of the fins geometry of a microchannel heat sink. The study was based on the Constructal Theory and proposes to develop a methodology to predict, in a deterministic way, the positioning and size of the heat sink fins. The method uses a construction function, which is dependent on velocity and temperature fields, to “guide” the construction. Main goal is to obtain arrangements with the lowest possible thermal resistance. The OpenFOAM software was used to solve the model equations using the Finite Volume method. The geometries were built from an empty domain to which fins were added. A total of 12 geometries were generated and best results were obtained with the geometries that better combined a large fins occupation area with a low coolant flow rate. It was also showed that there is a correct amount of solid which leads to the best thermal performance. Observing the best obtained configurations, it is clear that there is a limit to the material addition in the channel; flow restriction causes a drop in the flow rate which is not compensated by the increase in the heat sink solid volume.

About the sexual dimorphism of the crucian carp Carassius carassius (Cyprinidae)

The Crucian carp Carassius carassius (Linnaeus, 1758) is widely distributed in the Northern Eurasia. This is a medium-sized schooling fish, mainly its habitat is shallow water bodies overgrown of aquatic plants and slow flowing rivers. The Crucian carp is resistant to hypoxiaand fluctuations of water temperature. It is euryphage. In recent decades, there has been a widespread reduction in its range and a decline in numbers both in Western Europe and in Russia. In Western Siberia, Crucian carp was previously relatively numerous. Since the end of the 20th century, this species has a decrease reduces the number or complete extinction in some water bodies of the region. This provokes an increased interest to the peculiarities of the biology of this fish species, including the variability of its morphological characteristics in different types of water bodies and the environmental characteristics that determine them. We have revealed sexual dimorphism of C. carassius in 47% of the studied plastic characters: females have a longer head length, anteventral and antepectral distances, and males have ventroanal, ventrocaudal, anal-caudal and dorso-caudal distances. In addition, males have larger fins: the height of the dorsal and anal fins, the length of the pectoral, ventral, and lower lobe of the caudal fins are statistically significantly greater. There are differences in head morphology: males have the height of the head through the middle of the eye and diameter of eye are statistically significantly greater. There are no sexual dimorphism of C. carassius in countable morphological characters. The our data obtained make it necessary to take into account the sex composition of the samples when analyzing the features of the variability of the morphological features of the Crucian carp C. carassius.

Investigation of stepwise porosity and perforated fins in finned tube adsorption bed for adsorption refrigeration

Adsorption refrigeration is a green refrigeration technology. The characteristics of its key component, the adsorption bed, directly affect the operational performance of the entire system. In this study, two novel types of structures, stepwise porosity and perforated fins, were applied to three types of conventional finned tube adsorption beds to improve heat and mass transfer. Using the finite element analysis method, the impacts of porosities and perforations were systematically evaluated to clarify the application range and development potential of this new technology. The results indicate that the overall performance of the system using a finned tube adsorption bed with an annular outer fin is better than that of a plate outer fin and annular inner fin. Stepwise porosity can help maintain the system coefficient of performance (COP) and reduce the degradation of the specific cooling power (SCP) when the finned tube adsorption bed is designed with a long fin or large fin spacing. The perforated fin structure improved the refrigeration performance of the finned tube adsorption bed. Stepwise perforation affects the values of the COP to some extent, but the variations in the value of the SCP are minor. Stepwise perforation combined with stepwise porosity might be a potential structure for further improving heat and mass transfer in the adsorption bed.

Reducing slipstream velocities around high-speed trains through retractable stationary surfaces

The slipstream wake structures generated by the passing of high-speed rail vehicles represents a hazard to passengers and workers in close proximity, and as such, maximum allowable slipstream velocities are prescribed in regulations. In this article, the possibility of reducing peak slipstream velocities using retractable or foldable local surface modifications on a generic high-speed train is assessed using Improved Delayed Detached Eddy Simulation (IDDES) modelling. It is demonstrated that the danger imposed by the slipstream wake structures, as measured by the induced velocities recorded at a pair of parallel test lines, as dictated in the standards, could be reduced by designs employing each of three methods examined. The most dramatic reductions were generated by large fins at the train rear, which redirected the time-mean trailing vortex structures to one side of the vehicle. However, the most feasible control method for symmetrical slipstream reduction consisted of placing small rectangular plates perpendicular to the flow near the nose section of the train. The induced disruption to the flow was observed to increase wake turbulence in a region above the train, which appeared to interfere with the formation of the trailing vortex structures and reduce the intensity of the cross-stream oscillation.

The Effective and Exergy Efficiency of Multi-Pass Solar Air Collector with Longitudinal Fins: Analysis and Optimization

The present work investigates the exergy and effective efficiency of the multi-pass solar air collector with longitudinal fins by analysis approach and multi-objective optimization. The effect of 0.01-0.02 kg/s air flow rate, 15-35 mm collector depth, 1-3 m collector length, and 24.21-30.67 mm fin pitch was considered. The optimization was analyzed by the Preference Selection Index (PSI) method, with three maximum criteria: thermal efficiency, effective efficiency, and exergy efficiency. Mathematical models were solved by EES software. Results indicated that the multi-pass (TPLF and DPLF) type was better than the SPWF type by three criteria. The highest exergy efficiency of the TPLF and DPLF types was 6.696% and 5.636%. The greatest effective efficiency of the TPLF and DPLF types was 69.09% and 66.17%. Furthermore, the optimization results indicated that the three efficiency criteria of the DPLF type were 58.38%, 58.22%, and 4.491% for the best case; the three efficiency criteria of the TPLF type were 60.97%, 60.85%, and 5.439% for the best case. The worst configuration was the model with a short collector length, large collector depth, and large fin pitch. The collector efficiency decreased with decreased fin pitch for the configuration with the large collector length, short collector depth, and high mass flow rate.

Numerical Calculation of the Irreversible Entropy Production of Additively Manufacturable Off-Set Strip Fin Heat-Transferring Structures

In this manuscript, off-set strip fin structures are presented which are adapted to the possibilities of additive manufacturing. For this purpose, the geometric parameters, including fin height, fin spacing, fin length, and fin longitudinal displacement, are varied, and the Colburn j-factor and the Fanning friction factor are numerically calculated in the Reynolds number range of 80-920. The structures are classified with respect to their entropy production number according to Bejan. This method is compared with the results from partial differential equations for the calculation of the irreversible entropy production rate due to shear stresses and heat conduction. This study reveals that the chosen temperature difference leads to deviation in terms of entropy production due to heat conduction, whereas the dissipation by shear stresses shows only small deviations of less than 2%. It is further shown that the variation in fin height and fin spacing has only a small influence on heat transfer and pressure drop, while a variation in fin length and fin longitudinal displacement shows a larger influence. With respect to the entropy production number, short and long fins, as well as large fin spacing and fin longitudinal displacement, are shown to be beneficial. A detailed examination of a single structure shows that the entropy production rate due to heat conduction is dominated by the entropy production rate in the wall, while the fluid has only a minor influence.

A Bioinspired Cownose Ray Robot for Seabed Exploration.

This article presents the design and the experimental tests of a bioinspired robot mimicking the cownose ray. These fish swim by moving their large and flat pectoral fins, creating a wave that pushes backward the surrounding water so that the fish is propelled forward due to momentum conservation. The robot inspired by these animals has a rigid central body, housing motors, batteries, and electronics, and flexible pectoral fins made of silicone rubber. Each of them is actuated by a servomotor driving a link inside the leading edge, and the traveling wave is reproduced thanks to the flexibility of the fin itself. In addition to the pectoral fins, two small rigid caudal fins are present to improve the robot's maneuverability. The robot has been designed, built, and tested underwater, and the experiments have shown that the locomotion principle is valid and that the robot is able to swim forward, perform left and right turns, and do floating or diving maneuvers.

Hydrodynamic interaction of dorsal fin and caudal fin in swimming tuna

Tuna, which are known for high-performance swimming, possess a large crescent dorsal fin (DF) and a caudal fin (CF) that differ from those of other fishes. The hydrodynamic interaction between the DF and CF in tuna, which are represented by two tandem 3D flapping plates, is numerically explored in the present study. Hydrodynamic properties and wake structures of the models with and without a DF are compared to investigate the effects of the DF. The thrust on the CF is substantially enhanced by the DF, whereas the force on the DF is not affected by the CF. The constructive interaction between the leading-edge vortex (LEV) on the CF and the vortices shed from the dorsal fin (DFVs) is identified from 3D wake topology and 2D vorticity distributions. The circulation of spanwise vorticity quantitatively reveals that the LEV on the CF is strengthened by the same-signed DFV. The effect of the flapping phase of the CF is examined. The DF–CF interaction is sensitive to the flapping phase at a short spacing, whereas a long spacing between the two fins enables a robust constructive interaction in tuna swimming. A systematic study is carried out to explore the effects of the Strouhal number (St) and the Reynolds number (Re) on the interaction of the fins. The enhancement of thrust due to the DF is diminished at St = 0.63, whereas the Re does not substantially influence the constructive DF–CF interaction.