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1.
The aim of this study was to build an accurate computer-based model to study the water flow and drag force characteristics around and acting upon the human body while in a submerged streamlined position. Comparisons of total drag force were performed between an actual swimmer, a virtual computational fluid dynamics (CFD) model of the swimmer, and an actual mannequin based on the virtual model. Drag forces were determined for velocities between 1.5 m/s and 2.25 m/s (representative of the velocities demonstrated in elite competition). The drag forces calculated from the virtual model using CFD were found to be within 4% of the experimentally determined values for the mannequin. The mannequin drag was found to be 18% less than the drag of the swimmer at each velocity examined. This study has determined the accuracy of using CFD for the analysis of the hydrodynamics of swimming and has allowed for the improved understanding of the relative contributions of various forms of drag to the total drag force experienced by submerged swimmers.  相似文献   

2.
The aim of this study was to build an accurate computer-based model to study the water flow and drag force characteristics around and acting upon the human body while in a submerged streamlined position. Comparisons of total drag force were performed between an actual swimmer, a virtual computational fluid dynamics (CFD) model of the swimmer, and an actual mannequin based on the virtual model. Drag forces were determined for velocities between 1.5 m/s and 2.25 m/s (representative of the velocities demonstrated in elite competition). The drag forces calculated from the virtual model using CFD were found to be within 4% of the experimentally determined values for the mannequin. The mannequin drag was found to be 18% less than the drag of the swimmer at each velocity examined. This study has determined the accuracy of using CFD for the analysis of the hydrodynamics of swimming and has allowed for the improved understanding of the relative contributions of various forms of drag to the total drag force experienced by submerged swimmers.  相似文献   

3.
Understanding the relationships between front crawl swimming technique and the corresponding fluid dynamics is important to athletes seeking improved performance and an edge over their rivals. Computational fluid dynamics (CFD) swimming modelling provides a controlled and unobtrusive capability that provides many previously immeasurable quantities including full flow fields and information on the forces experienced by the body throughout the stroke. In this study, a coupled biomechanical-smoothed particle hydrodynamics (SPH) method is used to determine when peak arm thrust occurs and how the ratio of arm–leg thrust changes with stroke rate. A dynamic biomechanical model of a female national-level swimmer was generated from a three-dimensional laser body scan of the athlete and multi-angle videos of sub-maximal swimming trials. This was coupled to the SPH method to simulate the fluid moving around the body during front crawl swimming. Two distinct peaks in net streamwise thrust were found during the stroke coinciding with the underwater arm strokes. The peak arm thrust occurred during the transition from pull to push (left arm) and midway during the push (right arm). Finally, the ratio of arm thrust to leg thrust was found to increase with increasing stroke rate.  相似文献   

4.
This study investigated the basic fluid mechanics associated with the hydrodynamic drag of a human. The components of drag (frictionD SF, pressureD P and waveD W) on a human swimmer were analysed by applying classical fluid dynamic fundamentals. General methods of reducing drag were considered and the most probable method identified, applied and tested on swimsuit hydrodynamic drag. This study employed turbulators, either one (upper back) or three (across the upper back, the chest and across the buttocks), that were compared to an identical full body suit with no turbulators. Male and female elite competitive swimmers (n = 7 each) were towed in an annular pool to determine passive drag at speeds from 0.4 to 2.2 m s−1. The total drag was reduced by 11–12% by one turbulator and 13–16% by three turbulators. The total drag was decomposed intoD SF, DP andD W to determine the mechanisms responsible for the reduced total drag by the turbulators. The presence of the turbulators did not significantly increase friction or wave drag; however, flow was attached to the body as there was a significant reduction in pressure drag (19–41%), with the greatest reduction being for three turbulators (chest, back, buttocks). This study demonstrated the importance of pressure drag in determining total drag at high human swimming speeds, and that drag reducing technology can significantly reduce it, in this case by appropriately sized and placed turbulators.  相似文献   

5.
ABSTRACT

Ankle flexibility is critical to obtain a high swimming velocity in undulatory underwater swimming (UUS). The present study investigated the Froude (propelling) efficiency and three-dimensional (3D) kinematics of human UUS following the extrinsic restriction of the ankle by tape application. In Experiment 1, swimmers (9 male and 8 female college swimmers) performed UUS trials involving normal swimming (Normal) and swimming with tape application at the ankle (Tape). Kicking frequency was controlled in both settings. UUS kinematics were obtained with a two-dimensional motion analysis. Swimming velocity significantly decreased during swimming with tape application compared with that during normal swimming (Normal, 1.33 m·s?1; Tape, 1.26 m·s?1, p < 0.05). The Froude efficiency was not affected (Normal, 0.77; Tape, 0.76), and ankle plantar angle did not decrease during swimming (Normal, 159.02°; Tape, 160.38°). In Experiment 2, lower limb rotations of a male swimmer were analysed using 3D motion analysis under the same conditions as Experiment 1. An insufficient forefoot rotation was observed during downstroke kicks (the phase of the highest acceleration to forward direction). These findings suggest that UUS velocity is affected by the mobility of end effector.  相似文献   

6.
This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer’s potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m2 area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency.  相似文献   

7.
In this paper a video-based method to automatically track instantaneous velocities of a swimmer is presented. Single cameras were used to follow a marker (LED) attached to the body. The method is inspired by particle tracking techniques, traditionally used in the field of fluid dynamics, to measure local velocities of a fluid flow. During the validation experiment, a white LED was attached to the hip of a swimmer together with a speedometer. A swimmer performed four different stroke types. The velocity profiles using LED tracking were captured and showed less noise than the speedometer measurements. Only at times when the marker disappeared above the water surface due to body role in front crawl and backstroke swimming did the LED tracking fail to capture the athlete’s motion. The algorithm was tested in a 2D case with a single LED to illustrate the proof of principle, but should be suitable for implementation in a 3D analysis or multiple LED analysis.  相似文献   

8.
The optimisation of undulatory underwater swimming is highly important in competitive swimming performance. Nineteen kinematic variables were identified from previous research undertaken to assess undulatory underwater swimming performance. The purpose of the present study was to determine which kinematic variables were key to the production of maximal undulatory underwater swimming velocity. Kinematic data at maximal undulatory underwater swimming velocity were collected from 17 skilled swimmers. A series of separate backward-elimination analysis of covariance models was produced with cycle frequency and cycle length as dependent variables (DVs) and participant as a fixed factor, as including cycle frequency and cycle length would explain 100% of the maximal swimming velocity variance. The covariates identified in the cycle-frequency and cycle-length models were used to form the saturated model for maximal swimming velocity. The final parsimonious model identified three covariates (maximal knee joint angular velocity, maximal ankle angular velocity and knee range of movement) as determinants of the variance in maximal swimming velocity (adjusted-r2 = 0.929). However, when participant was removed as a fixed factor there was a large reduction in explained variance (adjusted r2 = 0.397) and only maximal knee joint angular velocity continued to contribute significantly, highlighting its importance to the production of maximal swimming velocity. The reduction in explained variance suggests an emphasis on inter-individual differences in undulatory underwater swimming technique and/or anthropometry. Future research should examine the efficacy of other anthropometric, kinematic and coordination variables to better understand the production of maximal swimming velocity and consider the importance of individual undulatory underwater swimming techniques when interpreting the data.  相似文献   

9.
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10.
To evaluate the propulsive forces in front crawl arm swimming, derived from a three-dimensional kinematic analysis, these values were compared with mean drag forces. The propulsive forces during front crawl swimming using the arms only were calculated using three-dimensional kinematic analysis combined with lift and drag coefficients obtained in fluid laboratories. Since, for any constant swimming speed, the mean propulsive force should be equal to the mean drag force acting on the body of the swimmer, mean values of the calculated propulsive forces were compared with the mean drag forces obtained from measurements on a Measuring Active Drag (MAD) system. The two methods yielded comparable results, the mean difference between them being only 5% (2 N). We conclude that propulsive forces obtained from three-dimensional kinematic analysis provide realistic values. The calculation of the propulsive force appears to be rather sensitive to the point on the hand at which the velocity is estimated and less sensitive to the orientation of the hand.  相似文献   

11.
Undulatory underwater swimming (UUS) occurs in the starts and turns of three of the four competitive swimming strokes and plays a significant role in overall swimming performance. The majority of research examining UUS is comparative in nature, dominated by studies comparing aquatic animals' undulatory locomotion with the UUS performance of humans. More recently, research directly examining human forms of UUS have been undertaken, providing further insight into the factors which influence swimming velocity and efficiency. This paper reviews studies which have examined the hydromechanical, biomechanical, and coordination aspects of UUS performance in both animals and humans. The present work provides a comprehensive evaluation of the key factors which combine to influence UUS performance examining (1) the role of end-effector frequency and body amplitudes in the production of a propulsive waveform, (2) the effects of morphology on the wavelength of the propulsive waveform and its subsequent impact on the mode of UUS adopted, and (3) the interactions of the undulatory movements to simultaneously optimise propulsive impulse whilst minimising the active drag experienced. In conclusion, the review recommends that further research is required to fully appreciate the complexity of UUS and examine how humans can further optimise performance.  相似文献   

12.
In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects’ legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s‐1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s‐1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.  相似文献   

13.
Measurement of active drag during crawl arm stroke swimming   总被引：2，自引：0，他引：2  
In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects' legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s-1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s-1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.  相似文献   

14.
Abstract

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.  相似文献   

15.
Propulsion, one of the most important factors in front crawl swimming performance, is generated from both the upper and lower limbs, yet little is known about the mechanisms of propulsion from the alternating movements of the lower limbs in the flutter kick (FK). The purpose of this systematic review was to review the literature relating to the mechanisms of propulsion from FK in front crawl. There was limited information about the mechanisms of propulsion in FK. Since movements of the lower limbs are similar between FK and the dolphin kick (DK), mechanisms of propulsion from DK were reviewed to better understand propulsion from FK. Recent evidence suggests that propulsion in DK is generated in conjunction with formation and shedding of vortices. Similar vortex structures have been observed in FK. Visualisation and simulation techniques, such as particle image velocimetry (PIV) and computational fluid dynamics (CFD), are non-invasive tools that can effectively model water flow without impacting swimming technique. These technologies allow researchers to estimate the acceleration of water and, consequently, the propulsive reaction forces acting on the swimmer. Future research should use these technologies to investigate propulsion from FK.  相似文献   

16.
靳钢 《湖北体育科技》2012,31(5):617-618,520
青少年游泳运动员作为中国游泳运动队的后备力量,他们的竞技水平将直接影响中国游泳的未来。对加强青少年游泳运动员体能训练的必要性和中国青少年游泳运动员体能训练中存在的弊端进行了分析,为中国青少年游泳运动员体能训练提出了建设性的建议,旨为在全面提高和发展我国游泳运动提供更好的指导和有益的参考。  相似文献   

17.
The purpose of this study was to test the hypothesis that the passive drag acting on a gliding swimmer is reduced if the swimmer adopts an abdominal breathing manoeuvre (expanding the abdominal wall) rather than chest breathing manoeuvre (expanding the rib cage). Eleven male participants participated in this study. A specialised towing machine was used to tow each participant with tension set at various magnitudes and to record time series data of towing velocity. Participants were asked to inhale air by expanding the abdominal wall or the rib cage and to maintain the same body configuration throughout gliding. The steady-state velocity was measured and the coefficient of drag was calculated for each towing trial to compare between the breathing manoeuvres. The results showed that the towing velocity was increased by 0.02 m/s with a towing force of 34.3 N and by 0.06 m/s with a towing force of 98.1 N. The coefficient of drag was reduced by 5% with the abdominal breathing manoeuvre, which was found to be statistically significant (p < 0.05). These results indicate that adopting the abdominal breathing manoeuvre during gliding reduces the passive drag and the hypothesis was supported.  相似文献   

18.
我国优秀游泳运动员途中游速度、划频、划幅变化的研究   总被引：5，自引：0，他引：5  
竞技游泳途中游的速度取决于划频和划幅两个因素。通过实验观测和比较,分析了我国最高水平游泳运动员成绩及途中游速度、划频、划幅的现状与变化情况,并结合身材、动作效率等因素,对如何调控划频、划幅以促进我国游泳运动员水平的进一步提高提出了参考意见。  相似文献   

19.
Active drag force in swimming can be calculated from a function of five different variables: swim velocity, tow velocity, belt force, power output and exponent of velocity. The accuracy of the drag force value is dependent on the accuracy of each variable, and on the contribution of each variable to drag estimation. To calculate uncertainty in drag value, first the derivatives of the active drag equation with respect to each variable were obtained. Second, these were multiplied by the uncertainty of that variable. Twelve national age and open level swimmers were recruited to complete four free swimming and five active drag trials. The uncertainties for the free and the tow swim velocities, and for the belt force, contributed approximately 5–6% and 2–3% error, respectively, in calculation of drag. The result of the uncertainty of the velocity exponent (1.8–2.6) indicated a contribution of about 6% error in active drag. The contribution of unequal power output showed that if a power changed 7.5% between conditions, it would lead to about 30% error in calculated drag. Consequently, if a swimmer did not maintain constant power output between conditions, there would be substantial errors in the calculation of active drag.  相似文献   

20.
We present a new method that combines the use of laser body scans, underwater video footage, software-based animation, and a fully unsteady computational fluid dynamics technique to simulate and examine the hydrodynamics of the dolphin kick. The focus of the current work is to model this particular stroke in all its complexity with minimal ad-hoc assumptions or simplifications. Simulations of one female and one male swimmer (both at about 1.7 m beneath the water surface) at velocities of 0.95 and 1.31 m/s and Strouhal numbers of 1.21 and 1.06 respectively are presented. Vorticity and fluid velocity profiles in the wake are examined in detail for both swimmers. A three-dimensional vortex ring is clearly identified in the wake for one of the cases and a two-dimensional slice through the ring corroborates previous experiments of Miwa et al. (2006). We also find that most of the thrust is produced by the feet and in both cases the down-kick produces much larger thrust than the up-kick.  相似文献   

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