Добірка наукової літератури з теми "Paddle propulsion"

Inspired by the forward swimming of long-tailed crustaceans, we study an underwater propulsion mechanism for a swimming body with multiple rigid paddles attached underneath undergoing cycles of power and return strokes with a constant phase-difference between neighboring paddles, a phenomenon known as metachronal propulsion. To study how inter-paddle phase-difference affects flux production, we develop a computational fluid dynamics model and a numerical algorithm based on the immersed boundary method, which allows us to simulate metachronal propulsion at Reynolds numbers (RE) ranging from close to 0 to about 100. Our main finding is that the highest average flux is generated when nearest-neighbor paddles maintain an approximate 20%–25% phase-difference with the more posterior paddle leading the cycle; this result is independent of stroke frequency across the full range of RE considered here. We also find that the optimal paddle spacing and the number of paddles depend on RE; we see a qualitative transition in the dynamics of flow generated by metachronal propulsion as RE rises above 80. Roughly speaking, in terms of average flux generation, a tight paddle spacing is preferred when RE is less than 10, but a wider spacing becomes clearly favored when RE is close to or above 100. In terms of efficiency of flux generation, at RE 0.1 the maximum efficiency occurs at two paddles, and the efficiency decreases as the number of paddles increases. At RE 100 the efficiency increases as the number of paddles increases, and it appears to saturate by eight paddles, whereas using four paddles is a good tradeoff for both low and intermediate RE.

In order to improve the swimming performance of a paddle-propelled crablike robot, the sequence and parameters of swimming gait are planned according to the bionic swimming mechanism. Based on the bionic prototype of Portunus trituberculatus, the structure scheme of a leg–paddle hybrid driven robot is proposed with the functions of walking on land, crawling on seabed, and swimming underwater. By analyzing the underwater propulsion mechanism of single paddle and hydrodynamic performance of double paddles cooperatively propulsion, four direct swimming gaits are planned and the corresponding attitude changes are theoretically analyzed. Then, the numerical simulation and direct swimming experiments are carried out to verify the effectiveness of proposed gaits and correctness of force analysis. In alternate swimming gait of lift-based mode, the robot swims forward in a rolling attitude, with an advantage of the minimum water resistance and the optimum swimming velocity and efficiency. The influence of flapping frequency and relative phases of paddles on the swimming velocity shows the trend of raise first and then fall.

The propulsion force of a kayaker can be measured thanks to sensors placed on the paddle. This article aims at linking this force to the evolution of the velocity of the boat. A general model is proposed to describe the motion of a K1 kayak. To validate the model and evaluate the relevant physics parameters, three on-water kayaking trials are proposed: a pure deceleration, a standing start, and 10 × 50 m with two athletes at the national level. These trials were performed with a force sensor on the paddle and video recording. We used the deceleration to evaluate the drag of the boat. Then the standing start showed that there was an active drag coefficient while kayaking. Finally, the 10 × 50 m exhibited a power law of one-third between the velocity and the stroke rate. The acceleration during the standing start together with the relationship between the velocity and stroke rate were well captured theoretically. This approach enabled us to evaluate the important parameters to describe a kayak race: the drag of the boat, an active drag coefficient, the mean propulsive force, and a propulsive length. It can be used to characterize athletes and monitor their performances.

The full comprehension of the impact with which each force is involved in kayak propulsion is very difficult. The measure of the force on the paddle or the stroke rate only is often not enough for the coach to identify the best actions useful to improve the performances of a kayaker. To this purpose, the synchronous measurement of all parameters involved in the kayak propulsion, both dynamic (force acting on paddle and foot brace) and kinematic (stroke frequency, displacement, velocity, acceleration, roll, yaw, and pitch of the boat) could suggest to the coach more appropriate strategies for better understanding of the paddler’s motion and the relevant effects on the kayak behavior. Some simulation models, as well as measurement systems of increasing complexity, have been proposed in the recent years. In this paper, we present the e-Kayak system: A multichannel Digital Acquisition (DAQ) system specifically customized for flatwater kayaking. The system will be described in depth and its capability investigated through specific measurement results.

AbstractReconstructing the swimming capabilities of extinct marine tetrapods is critical for unravelling broader questions about their palaeobiology, palaeoecology and palaeobiogeography. Ichthyosaurs have long been the subject of such investigations because, alongside cetaceans, they are one of the few tetrapod lineages to achieve a highly specialized fish-like body plan. The dominant locomotory mode for the majority of derived, post-Triassic ichthyosaurs is hypothesized to have been caudal fin-driven propulsion. Limb-based swimming has however been suggested for some highly autapomorphic forms, such as the Cretaceous genus Platypterygius, which has a remarkably robust humeral morphology and exceptionally broad paddle-like limbs. To evaluate this atypical lifestyle model, we conducted a comprehensive comparative osteological assessment of Platypterygius in relation to extant marine mammals, whose analogous skeletal frameworks provide a structurally compatible selection of alternate propulsive strategies. Based on a proxy exemplar of the most completely known species, P. australis from the Early Cretaceous of Australia, the propodial shape, absence of functional elbow/knee joints, tightly interlocking carpals, hyperphalangy and extreme reduction of the pelvic girdle are most similar to cetaceans as opposed to pinnipeds or dugongs. There is no obvious structural consistency with aquatic mammals that use sustained forelimb-driven swimming. The exceptionally broad fore-paddle (a product of hyperdactyly) and extensive humeral muscle insertions might therefore have had a cetacean-like role in enhancing manoeuvrability and acceleration performance. We conclude that, despite its atypical features, P. australis was most likely similar to other ichthyosaurs in using lateral sweeps of the tailfin to generate primary propulsive thrust.

Abstract Secondary aquatic vertebrates exhibit a diversity of swimming modes that use paired limbs and/or the tail. Various secondarily aquatic tetrapod clades, including amphibians, reptiles, and mammals use transverse undulations or oscillations of the tail for swimming. These movements have often been classified according to a kinematic gradient that was established for fishes but may not be appropriate to describe the swimming motions of tetrapods. To understand the evolution of movements and design of the tail in aquatic tetrapods, we categorize the types of tails used for swimming and examine swimming kinematics and hydrodynamics. From a foundation of a narrow, elongate ancestral tail, the tails used for swimming by aquatic tetrapods are classified as tapered, keeled, paddle, and lunate. Tail undulations are associated with tapered, keeled, and paddle tails for a diversity of taxa. Propulsive undulatory waves move down the tail with increasing amplitude toward the tail tip, while moving posteriorly at a velocity faster than the anterior motion of the body indicating that the tail is used for thrust generation. Aquatic propulsion is associated with the transfer of momentum to the water from the swimming movements of the tail, particularly at the trailing edge. The addition of transverse extensions and flattening of the tail increases the mass of water accelerated posteriorly and affects vorticity shed into the wake for more aquatically adapted animals. Digital Particle Image Velocimetry reveals that the differences were exhibited in the vortex wake between the morphological and kinematic extremes of the alligator with a tapering undulating tail and the dolphin with oscillating wing-like flukes that generate thrust. In addition to exploring the relationship between the shape of undulating tails and the swimming performance across aquatic tetrapods, the role of tail reduction or loss of a tail in aquatic-tetrapod swimming was also explored. For aquatic tetrapods, the reduction would have been due to factors including locomotor and defensive specializations and phylogenetic and physiological constraints. Possession of a thrust-generating tail for swimming, or lack thereof, guided various lineages of secondarily aquatic vertebrates into different evolutionary trajectories for effective aquatic propulsion (i.e., speed, efficiency, and acceleration).

Abstract The paper provides simulation results for SUP (Stand Up Paddle) board appendage resistance. Additional propulsion is added to the SUP board. It is equipped with a waterjet. The waterjet is attached to the board rudder. This increases the drag coefficient for rudder five times. To reduce the drag variable, design options for the waterjet duct were proposed. The simulation tests were performed using SolidWorks Flow software using two types of simulations, namely, the pressure on the body and the flow around the body. The objective was to streamline the bluff duct of the waterjet and thus to create the appendage design with minimum drag force from fluid flow and possibly greater Inlet Velocity Ratio. Calculations showed that rounding-off the edges of waterjet duct resulted in 35 % of drag coefficient reduction, while further streamlining reduced it by additional 10 %.

Orientador: Orival Andries Júnior
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Educação Física
Made available in DSpace on 2018-08-16T18:10:16Z (GMT). No. of bitstreams: 1 Barbosa_AugustoCarvalho_D.pdf: 7576445 bytes, checksum: 04d87ab5c33f1dc5ca635490134e7f67 (MD5) Previous issue date: 2010
Resumo: O objetivo do presente estudo foi analisar as respostas agudas de parâmetros biomecânicos à utilização de diferentes tamanhos de palmar no nado crawl. Foram selecionados 14 nadadores homens (idade: 20.0 ± 3.7 anos, altura: 1.84 ± 0.08 m, massa corporal: 76.3 ± 8.6 kg, melhor tempo nos 100 m livre: 53.70 ± 0.87 s) competitivos em nível nacional. Para avaliação da força propulsora foram realizados 02 esforços máximos de 10 s no nado completamente atado. Em cada um foram analisadas 08 braçadas consecutivas, de onde se extraiu os valores médios de força pico (Fpico), força média (Fméd), taxa de desenvolvimento de força (TDF), impulso (ImpF), duração da braçada (DUR), tempo para atingir a força pico (TFpico) e força mínima (Fmín). Os nadadores também realizaram 02 esforços máximos na distância de 25m para obtenção da velocidade média em 15m (VM15m) (foram desprezados os 07 primeiros e 03 últimos metros), da frequência (FB15m) e do comprimento de braçadas (CB15m). Ambos os protocolos foram repetidos em 05 situações, a saber: livre de material (LVR), com palmar pequeno (PP, 280 cm²), médio (PM, 352 cm²), grande (PG, 462 cm²) e extragrande (PGG, 552 cm²). A ANOVA one way e o teste de Kruskal-Wallis foram adotados para comparar as situações. Quando detectado um efeito significante, recorreu-se ao teste de post-hoc de Scheffé (dados paramétricos) ou ao teste de Mann-Whitney com ajuste de Bonferroni (dados não-paramétricos) para localização das diferenças. Foi adotado um nível de significância de 5%. O aumento artificial da área da mão possibilitou o deslocamento de uma maior massa de água ocasionando um incremento significante na Fpico nas comparações LVR x PG, LVR x PGG e PP x PGG. Com isso, houve uma diminuição da velocidade da mão, que repercutiu em um aumento da DUR nessas mesmas comparações. Fméd e/ou TDF não apresentaram modificações significantes devido às alterações concomitantes das variáveis cinéticas e temporais que as influenciam. Esse resultado da TDF, aliado ao aumento do ImpF (principal variável associada à velocidade) nas comparações LVR x PG, LVR x PGG e PP x PGG, pode indicar que PG e PGG propiciam o desenvolvimento da propulsão sem ocasionar prejuízos aparentes na capacidade explosiva dos nadadores. O TFpico aumentou de LVR para PGG e PP para PGG devido ao aumento da Fpico e da diminuição da Fmín. A Fmín diminuiu significantemente apenas de LVR para PGG, apontando para uma possível alteração da relação entre o início e término da propulsão de ambos os braços. A ausência de alterações significantes na VM15m pode estar associada ao aumento do arrasto de onda. A FB15m diminuiu significantemente de LVR para PGG e de PP para PGG, enquanto o CB15m apresentou um comportamento exatamente inverso nas mesmas comparações. Conclui-se que, de forma aguda, o tamanho do palmar influencia principalmente a magnitude da força propulsora gerada e o seu comportamento ao longo do tempo
Abstract: The aim of this study was to analyze the acute responses of biomechanical parameters to different sizes of paddles in front-crawl stroke. Fourteen national competitive male swimmers (Age: 20.0 ± 3.7 years, height: 1.84 ± 0.08 m, body mass: 76.3 ± 8.6 kg, 100- m best time: 53.70 ± 0.87 s) volunteered for this investigation. For the propulsive force evaluation, 02 maximum efforts of 10 s were accomplished in the fully tethered swimming. In each effort, 08 consecutive strokes were analyzed to extract the average value of peak force (Fpeak), mean force (Fmean), explosive force (TDF), impulse (ImpF), stroke duration (DUR), time to peak force (TFpeak) and minimum force (Fmin). Additionally, swimmers accomplished two 25-m maximal swimming in order to measure the average velocity in 15 m (VM15m) (first 07 and last 03m were discarded), the stroke rate (SR15m) and the stroke length (SL15m). Both testing protocols were repeated in 05 conditions: conventional swimming (LVR), wearing small (PP, 280 cm²), medium (PM, 352 cm²), large (PG, 462 cm²) and extra-large paddles (PGG, 552 cm²). The one way ANOVA or the Kruskal-Wallis test were adopted for intersituations comparisons. Possible significant differences were detected by Scheffé post-hoc test (for parametric data) or Mann-Whitney test with Bonferroni adjustment (for non-parametric data). The significance level was set at 5%. The artificial enlargement of the hands allowed the swimmers to push off against a bigger mass of water and provided a significant increase of the Fpeak in the comparisons LVR x PG, LVR x PGG and PP x PGG. Because of this, there was also a hand's velocity reduction, which repercuted in a greater DUR in these same comparisons. The Fmean and/or the TDF did not change significantly due to the concomitant modifications of the kinetic and temporal variables that influence them. This result of the TDF, associated to the increase of the ImpF (the main variable related to swimming velocity) in the comparisons LVR x PG, LVR x PGG and PP x PGG, might indicate that PG and PGG propitiate the development of propulsion without any apparent damage in the swimmer's explosiveness. The TFpeak increased from LVR to PGG and from PP to PGG due to the increase of the Fpeak and the decrease of Fmin. The Fmin decrease significantly only from LVR to PGG, pointing to a possible modification in the relation between the beginning and the end of propulsion of both arms. The absence of significant changes in the VM15m might be related to the wave drag increase. The SR15m decrease significantly from LVR to PGG, while the SL15m presented exactly the inverse behavior. It can be concluded that, acutely, the different sizes of hand paddles influence mainly the magnitude of the propulsive force generated and its behavior throughout the time
Doutorado
Ciencia do Desporto
Doutor em Educação Física

Wireless applications have become a common part of daily life. Whether it is mobile phones, the Wi-Fi router at home, the keycard which has replaced the car key, a radio frequency identification access system to a building or a Bluetooth headset for your computer or phone, the means of modern wireless data exchange is an omnipresent technology. In sports, the market is in its infancy for wireless, technical applications or gadgets. Only heart rate monitors and GPS watches are currently used by recreational athletes. Even though most of the larger sports equipment companies regularly launch new products related to sports performance monitoring and mobile phone technology, product innovation leaps are rare.In this work the design of a wireless sports performance measurement platform is presented. Using the example of kayaking, this platform is configured as a paddle performance measuring system, the Kayak XL System, which can monitor propulsive paddle force, paddle kinematics and boat velocity, interalia. A common mobile phone platform has been chosen as the user interface for this system. The design approach focussing on user requests, demands and expectations in combination with the process of iterative technical development are unveiled in this thesis. An evaluation of the system is presented and the work is finalised with an overview of further systems which have been designed based on the developed measurement platform. The Kayak XL System is a flexible system designed to be mounted onto any standard kayak paddle and installed in any competition kayak. Versatility, unobtrusiveness and usability were major design concerns. The developed system consists of four modules plus a software which has been designed for Android mobile phones. The phone communicates with each of the four modules trough Bluetooth radio. These four modules are also referred to as nodes and have specific measurement purposes. Two nodes have been designed to measure paddle force and kinematics, one node has the purpose to measure foot stretcher force and boat motion data, and the fourth node enables a more convenient method of calibrating paddle force measurement. The fourth node is therefore only needed prior to performance data acquisition. Results show that paddle and foot stretcher force can be measured with a resolution below 1N after calibration. Installing the paddle nodes on a previously configured paddle without repeated calibration is facilitated with the compromise of a doubled error margin. The default sampling frequency is set to 100 Hz and can, like all system parameters, be configured on the mobile phone. Real-time computation of complex performance parameters is only limited by the phone CPU. The system adds twice 109 g to the paddle and approximately 850 g to the kayak, excluding the mass of the mobile phone

QC 20120827

In dragon boat racing, boat speed is generated by paddle propulsion produced by human movement. However at the fundamental level it is the interaction of the paddle with water that produces the forces generating boat speed. Literature on the biomechanics of paddle propulsion is sparse and is concerned predominantly with human movement and not with the fundamentals of paddling. This thesis examines the biomechanics of dragon boat paddling from the perspective of the paddle. Kinetic and kinematic paddle data were collected sequentially for each test participant from two dragon boat crews via 30 s maximum effort paddling tests. A custom built strain-gauged paddle sampled the paddling forces at 200 Hz whilst a stationary video camera (Sony HDR-HC7) recorded a single representative racing paced paddling stroke at 200 Hz. A light flash recorded by the video camera and its trigger signal recorded by the force data collection system ensured synchronisation. Excel spreadsheets converted the data into kinetic and kinematic paddle parameters for each study. Study one operationalised a qualitative coaching model for teaching paddlers a good dragon boat paddling stroke and produced strong support for the coaching model via a statistical comparison of more skilled paddlers with paddlers less skilled. More skilled paddlers produced significant superior results for paddle reach at water contact, rate of force development on water entry, maximum paddle force, drive impulse and drive impulse rate, force rate reduction at paddle exit and paddle impulse during recovery. Study two investigated the kinetic, kinematic and temporal paddle parameters that differentiate a more successful dragon boat racing crew from a less successful crew. The more successful racing crew produced significant superior results for rate of force development during water entry, average drive force, average peak to drive force ratio, rate of force reduction at paddle exit, paddle reach at water contact, paddle angle at maximum force, average paddle angular velocity in water, paddle displacement on the water surface, the stroke length, and the time duration of the catch and the paddling stroke. Study three examined the kinetic and temporal paddle parameters that differentiate more skilled paddlers from the less skilled. More skilled paddlers produced significant superior results for the rate of force development during paddle entry, maximum paddle force, paddle force at vertical position, average force during the catch and drive phases of the paddling stroke, average peak to drive force ratio, rate of force reduction at paddle exit, drive impulse, drive impulse rate, stroke impulse during recovery. And the time duration of the catch and drive phases of the addling stroke. Study four, the final study, established the kinematic paddle parameters that differentiate more skilled paddlers from paddlers less skilled. The more skilled paddlers produced significant superior results for paddle reach at water contact, average paddle angular velocity in water, paddle displacement on the water surface and paddle angle at water exit. Together these four studies provide a biomechanical foundation for the sport of dragon boat racing. Coaches and paddlers can use the findings of this thesis to improve paddling technique, paddling skill and racing performance.

Traditionally, sailing ships were commanded from the quarter deck, aft of the mainmast. With the arrival of paddle steamers, engineers required a platform from which they could inspect the paddle wheels and where the captain's view would not be obstructed by the paddle houses. A raised walkway, literally a bridge, connecting the paddle houses was therefore provided. When the screw propeller superseded the paddle wheel, the bridge was retained. Commands would be passed from the senior officer on the bridge to stations dispersed throughout the ship, where physical control of the ship was exercised, as technology did not exist for the remote control of steering or machinery. Helm orders would be passed to an enclosed wheel house, where the coxswain or helmsman operated the ship's wheel. Engine commands would be relayed to the engineer in the engine room by an engine order telegraph, which displayed the captain's orders on a dial. The engineer would ensure that the correct combination of steam pressure and engine revolutions were applied. The bridge was often open to the elements, therefore a weatherproof pilot house could be provided, from which a pilot, who was traditionally the ship's navigating officer, could issue commands from shelter. Iron, and later steel, ships also required a compass platform. This was usually a tower, where a magnetic compass could be sited far away as possible from the ferrous interference of the hulk of the ship. Depending upon the design and layout of a ship, all of these terms can be variously interchangeable. Many ships still have a flying bridge, a platform atop the pilot house, open to weather, containing a binnacle and voice tubes to allow the conning officer to direct the ship from a higher position during fair weather conditions. The concept was that the higher you are situated, the better and farther you could see. Larger ships, often had a navigation bridge which would be used for the actual conning of the ship. Modern advances in remote control equipment have seen progressive transfer of the actual control of the ship to the bridge. The wheel and engines can be operated directly from the bridge, controlling often-unmanned machinery spaces. Today, Monkey Island and Crow’s nest have become so archaic that people have forgotten their meaning as they have been deleted from contemporary marine glossaries.

The adaptation of steam engines for marine propulsion caused a dramatic shift in naval and commericial ship design during the 19th Century. The transition from sail to steam hastened the demise of several classes of ships and altered shippings routes from the trade winds to great circle routing. The conduct of naval warfare was always influenced by the limits of available propulsion technology. Throughout maritime history, innovative naval commanders sought ways to overrun, outmaneuver, and outlast their opponents. Coincident developments in armaments and armor, facilitated by this “new” propulsion technology, rendered the world’s sailing navies largely obsolete within a relatively brief period of the 19th Century. This presentation highlights the major technological advances in steam propulsion from the early combination of low-speed single-acting reciprocating engines driving paddle wheels through high-speed turbines and reduction gears driving multiple-blade variable-pitch propellers; and, boilers heated by hand-fed wood and coal through nuclear fission.

Abstract Success of emerging field of soft robotics relies on the development of efficient soft actuators. Most of these actuators suffers from disadvantages such as limited blocking force, lifetime, high actuation voltage, and slow response time. Swimming robots in particular utilizes single or multiple soft actuators to mimic the dynamic of a fish during motion. In this study we used 3D printing to fabricate soft electromagnetic actuators based swimming robot. The mechanism consists of soft actuator legs, compliant paddle and floatation. We designed a hybrid propulsion mechanism by using double soft leg actuators as caudal fins and side paddles as pectoral fins. This increases the thrust and efficiency to overcome the water drag as well as providing stability. We 3D printed the soft actuator using thermoplastic polyurethane (TPU) filament to reduce the manufacturing cost as well as to simplify the process. The main body is also 3D printed using polylactic acid (PLA). The infill percentage of the soft body is adjusted to increase the bending performance without yielding under actuation. The prototype of the swimming robot was tested in water. The body velocity of the robot is measured as 0.106 BL/s. Motion analysis was made MSC Adams by simulating the deformation of flexible beams.

Abstract Metachronal motion is a unique swimming strategy widely adopted by many small animals on the scale of microns up to several centimeters (e.g., ctenophores, copepods, krill, and shrimp). During propulsion, each evenly spaced appendage performs a propulsive stroke sequentially with a constant phaselag from its neighbor, forming a metachronal wave. To produce net thrust in the low-to-intermediate Reynolds number regime, where viscous forces are dominant, the beat cycle of a metachronal appendage must present significant spatial asymmetry between the power and recovery stroke. As the Reynolds number increases, the beat cycle is observed to change from high spatial asymmetry to lower spatial asymmetry. However, it is still unclear how the magnitude of spatial asymmetry can modify the shear layers near the tip of appendages and thus affect its associated hydrodynamic performance. In this study, ctenophores are used to investigate the hydrodynamics of multiple appendages performing a metachronal wave. Ctenophores swim using paddle-like ciliary structures (i.e., ctenes), which beat metachronally in rows circumscribing an ovoid body. Based on high-speed video recordings, we reconstruct the metachronal wave of ctenes for both a lower spatial asymmetry case and a higher spatial asymmetry case. An in-house immersed-boundary-method-based computational fluid dynamics solver is used to simulate the flow field and associated hydrodynamic performance. Our simulation results aim to provide fundamental fluid dynamic principles for guiding the design of bio-inspired miniaturized flexible robots swimming in the low-to-intermediate Reynolds number regime.

Aqua is an underwater biomimetic vehicle designed and built at McGill University that uses six paddles to produce control and propulsion forces. It has the particularity of having time-periodic thrust due to its oscillating paddles. Using an existing model of the vehicle, two types of controller were developed: a PD controller and a Floquet controller. The Floquet controller has the advantage of explicitly addressing the time-periodicity of the system. The performance of the controllers was assessed experimentally in the Caribbean Sea. We find that the vehicle was able to follow the prescribed trajectories with relative accuracy using both controllers. However, the Floquet controller slightly outperforms the PD controller. Furthermore, a key advantage of the Floquet controller is that it requires no tuning while the PD controller had to be tuned by trial and error.