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1.
Flight dynamics of the screw kick in rugby 总被引：1，自引：1，他引：0
This paper describes the aerodynamic forces and the flight trajectory for the screw (spiral) kick in rugby. The screw kick
is defined as that which causes the ball to spin on its longitudinal axis. The aerodynamic forces acting on a rugby ball spinning
on its longitudinal axis were measured in a wind tunnel using a six-component strut type balance. It was found that the drag,
the lift and the pitching moment depend on the angle of attack, while the side force (Magnus force) depends on both the spin
rate and the angle of attack in the range where the wind speed lies between 15 and 30 m s-1 and the spin rate is between 1 and 10 revolutions per second. Moreover, the flight trajectory was obtained by integrating
the full nonlinear six degrees of freedom equations of motion on the basis of aerodynamic data. In a simulation, a ball spinning
on its longitudinal axis tended to hook toward or away from the touchline even if the velocity and angular velocity vectors
were parallel to the touchline. The direction of the hook depends on the direction of the angular velocity vector. The initial
direction of the hook depends on the relationship between the flight path angle and the pitch angle as well as the direction
of the angular velocity vector. 相似文献
2.
The spin-stabilised sports disc, more commonly known as the Frisbee, is used for a variety of recreation and sporting activities.
Frisbees have unique flying characteristics compared to other sports projectiles because they depend on spin for stability
during flight and, at typical launch speeds, aerodynamic lift is greater than or equal to the weight of the disc. In this
paper, a six degree of freedom mathematical model of a spinning disc wing is developed and a simple analytical expression
derived for the disc roll rate in straight and level flight. It is shown that dimensionless disc trajectories will be similar
for similar values of a parameter based on the ratio of the disc static margin to the disc advance ratio. The mathematical
model is implemented as a simulation in Matlab using steady model parameters obtained from wind tunnel tests and unsteady
parameters from flight tests. Simulation results are shown to be in reasonable agreement with limited available experimental
flight data. The effect of launch conditions has been investigated using a series of numerical experiments. It is found that
flight path curvature in the horizontal plane increases with decreasing advance ratio, as expected. Pitch angles at launch
for maximum range and maximum duration are approximately 10° and 20° respectively. Also, the locus of disc landing position
as a function of launch roll angle has been shown to be an ‘S’ shaped curve, with the straightest flight occurring for an
initial roll angle of-6°. Finally, the simulation has been extended to include the effects of hypothetical control inputs,
enabling simulation of novel Frisbee manoeuvres. 相似文献
3.
The aim of this study was to develop a new method for the determination of lift on spinning baseballs. Inertial trajectories of (a) ball surface markers during the first metre of flight and (b) the centre of mass trajectory near home-plate were measured in a pitch using high-speed video. A theoretical model was developed, incorporating aerodynamic Magnus-Robins lift, drag and cross forces, which predicts the centre of mass and marker trajectories. Parameters including initial conditions and aerodynamic coefficients were estimated iteratively by minimizing the error between predicted and measured trajectories. We compare the resulting lift coefficients and spin parameter values with those of previous studies. Lift on four-seam pitches can be as much as three times that of two-seam pitches, although this disparity is reduced for spin parameters greater than 0.4. 相似文献
4.
The aim of this study was to develop a new method for the determination of lift on spinning baseballs. Inertial trajectories of (a) ball surface markers during the first metre of flight and (b) the centre of mass trajectory near home-plate were measured in a pitch using high-speed video. A theoretical model was developed, incorporating aerodynamic Magnus-Robins lift, drag and cross forces, which predicts the centre of mass and marker trajectories. Parameters including initial conditions and aerodynamic coefficients were estimated iteratively by minimizing the error between predicted and measured trajectories. We compare the resulting lift coefficients and spin parameter values with those of previous studies. Lift on four-seam pitches can be as much as three times that of two-seam pitches, although this disparity is reduced for spin parameters greater than 0.4. 相似文献
5.
In this paper, an analytical and numerical study of the three-dimensional equations describing the motion through the air of a spinning ball is presented. The initial analysis involves constant drag coefficients, but is later extended to involve drag varying with the spin ratio. Excellent agreement is demonstrated between numerical, analytical and experimental results. The analytical solution shows explicitly how the ball’s motion depends on parameters such as ball roughness, velocity and atmospheric conditions. The importance of applying three-dimensional models, rather than two-dimensional approximations, is demonstrated. 相似文献
6.
To determine the flight of a ski jumper it is essential to know what aerodynamic forces are acting on the ski jumper. However,
few data on this are available, especially for a V-style ski jumping flight. We have measured the aerodynamic forces during
the free flight phase for a V-style, as well as a parallel-style, ski jump by employing a full-size model in a wind tunnel.
The aerodynamic force data, (drag, lift and pitching moment) were obtained to create an aerodynamic database. These forces
are given in polynomial form as functions of the angle of attack, the body-ski (forward leaning) angle and the ski-opening
(V-style) angle. Using the polynomial form database is a convenient way of obtaining the aerodynamic forces. Moreover, the
wind tunnel was equipped with a ground effect plate to measure the aerodynamic forces during the landing phase. It was found
that the difference between the lift with and without the ground effect plate increases with the ski-opening angle. The longitudinal
stability in the pitching motion of a body-ski combination is also discussed on the basis of the pitching moment data. This
indicates that a stable pitching oscillation of the body-ski combination may arise around an equilibrium point in the angle
of attack, the trim angle of attack, during flight. 相似文献
7.
Masahide Murakami Masato Iwase Kazuya Seo Yuji Ohgi Reno Koyanagi 《Sports Engineering》2014,17(4):217-225
Ski jumping flight posture was analyzed for achieving large flight distance on the basis of high-speed video images of the initial 40 m part of 120-m ski jumping flight. The time variations of the forward leaning angle and the ski angle of attack were measured from the video images, and the aerodynamic forces were calculated from the kinematic data derived from the images. Some correlations were investigated between the initial-speed corrected flight distance and such parameters as the angles of jumper, the initial transition time and the aerodynamic force coefficients. The result indicated that small body angle of attack was a key for large flight distance in the initial phase of flight because of small drag force, and that the most distinctive fault of beginners was too large body angle of attack and ski angle of attack leading to aerodynamic stall. Too small drag force does not give an optimal condition for large flight distance because the lift force is also too small. The ratio of the lift to the drag was larger than 0.95 for advanced jumpers. 相似文献
8.
An overview of cricket ball swing 总被引：1，自引：0，他引：1
Rabindra D. Mehta 《Sports Engineering》2005,8(4):181-192
The aerodynamic properties of a cricket ball have intrigued cricket players and spectators for years, arguably since the advent
of the game itself. The main interest is in the fact that the ball can follow a curved flight path that may not always be
under the control of the bowler. The basic aerodynamic principles responsible for the nonlinear flight or ‘swing’ of a cricket
ball were identified decades ago and many papers have been published on the subject. Over the last 25 years or so, several
empirical investigations have also been conducted on cricket ball swing, which revealed the amount of attainable swing and
identified the parameters that affect it. Those findings are reviewed here with emphasis on phenomena such as late swing and
the effects of humidity on swing. The relatively new concept of ‘reverse swing’, how it can be achieved in practice, and the
role in it of ‘ball tampering’, are also discussed in detail. In particular, the ability of some bowlers to effectively swing
an old ball in the conventional, reverse and the newly termed ‘contrast’ swing mode is addressed. A discussion of the ‘white”
cricket ball used in the 1999 and 2003 World Cup tournaments, which supposedly possesses different swing properties compared
to a conventional red ball, is also included. This is a current overview of cricket ball swing rather than a detailed review
of all research work performed on the topic. The emphasis is on presenting scientific explanations for the various aerodynamic
phenomena that affect cricket ball swing on a cricket ground. 相似文献
9.
A badminton shuttlecock flies in a high-drag, and thus, the sport has been a subject of research from the point of view of aerodynamics. A badminton shuttlecock generates significant aerodynamic drag and has a complex flight trajectory. It also has the smallest ballistic coefficient and exhibits the largest in-flight deceleration of any airborne sporting projectile. The ballistic coefficient of a projectile is a measure of its ability to overcome air resistance in flight and is inversely proportional to deceleration. The primary objectives of this study were to measure the aerodynamic properties of feather shuttlecocks under a range of the wind speed (10–60 m/s) and pitch angle (0°–25°). In particular, measurements of aerodynamic forces were performed at high Reynolds numbers (more than Re = 210,000), and the effect of shuttlecock deformation on aerodynamic properties was also investigated, because it is presumed that the flight dynamics is affected by the deformation of the shuttlecock skirt. A shuttlecock skirt is composed of an array of diverging stems, the ends of which are at the convergent end of the skirt, joined together in an end ring. The shuttlecock rotates about its major axis in actual flight, and thus, the experiments were performed on shuttlecocks with and without rotation (spin). Furthermore, the effect of the flow passing through the gaps between the slots (stiffeners) located at the leg portion of the shuttlecock skirt on aerodynamic characteristics is demonstrated by means of a shuttlecock model without gaps, which was completely covered with cellophane tape. The free rotation rate of a shuttlecock increased with an increase in the Reynolds number, and the drag coefficient gradually decreased above Re = 86,000 for a non-rotating shuttlecock. The reduction of drag can be explained by the deformation of the skirt observed in wind tunnel experiments at high speed. In this study, for a rotating shuttlecock, a reduction of drag was not observed over a whole range of Reynolds numbers, because deformation of the skirt for a rotating shuttlecock becomes smaller than that for a non-rotating shuttlecock. However, there was no significant difference in drag coefficient between rotating and non-rotating shuttlecocks, in contrast to the difference in drag coefficient between shuttlecocks with and without gaps. The drag coefficient for a shuttlecock without gaps was significantly smaller than that for a standard shuttlecock (with gaps). For a standard shuttlecock, the air flowed through the gaps into the shuttlecock skirt, and this flow was related to high aerodynamic drag. 相似文献
10.
When the boundary layer of a sports ball undergoes the transition from laminar to turbulent flow, a drag crisis occurs whereby
the drag coefficient (C
d) rapidly decreases. However, the aerodynamic properties and boundary-layer dynamics of a soccer ball are not yet well understood.
In this study we showed that the critical Reynolds number (Re
crit) of soccer balls ranged from 2.2 × 105 to 3.0 × 105. Wind-tunnel testing, along with visualisation of the dynamics of the boundary layer and the trailing vortex of a ball in
flight, demonstrated that both non-spinning and spinning (curved) balls had lowC
d values in the super-critical region. In addition, theRe
crit values of the soccer balls were lower than those of smooth spheres, ranging from ∼ 3.5 × 105 to 4.0 × 105, due to the effects of their panels. This indicated that the aerodynamic properties of a soccer ball were intermediate between
those of a smooth ball and a golf ball. In a flow visualisation experiment, the separation point retreated and theC
d decreased in a super-critical regime compared with those in a sub-critical regime, suggesting a phenomenon similar to that
observed in other sports balls. With some non-spinning and spinning soccer balls, the wake varied over time. In general, the
high-frequency component of an eddy dissipated, while the low-frequency component increased as the downstream vortex increased.
The causes of the large-scale fluctuations in the vortex observed in the present study were unclear; however, it is possible
that a ‘knuckle-ball effect’ of the non-rotating ball played a role in this phenomenon. 相似文献
11.
Tom Wu Pierre Gervais 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):88-99
Many slo-pitch coaches and players believe that generating spin on a ball can affect its trajectory. The influence of air resistance on a ball that is thrown at a moderate speed and spin is unclear. The aim of this study was to examine the influence of spin on the ball's trajectory in slo-pitch pitching using both experimental results and ball flight simulations. Fourteen pitchers participated in the study, each of whom threw five backspin and topspin pitches each. Data were collected using standard three-dimensional videography. The horizontal velocity, vertical velocity, angular velocity, release height, and horizontal displacement of the backspin pitches were significantly higher than those of the topspin pitches. The ball flight simulations were developed to examine the influence of the ball spin, and it was concluded that the spin of the ball had a significant effect on the ball's vertical and horizontal displacements. Furthermore, our results suggest that a backspin pitch that reaches the maximum height allowable and lands in the front edge of the strike zone has the steepest slope. The present results add to our understanding of projectile motion and aerodynamics. 相似文献
12.
This paper describes the use of Pareto-optimal solutions for the screw kick in rugby. We attempted to optimise the initial
conditions for a screw kick. The optimisation was carried out using an elitist non-dominated sorting genetic algorithm. Distance
achieved in flight is considered as an objective function, as well as the lateral deviation between the ball and the touchline,
or the flight time. Six initial conditions were defined as control parameters: the magnitude of the velocity vector, the flight
path angle, the azimuth angle, the spin rate, the pitch angle and the yaw angle. The results are summarised as follows: it
is impossible for both objective functions to be satisfied simultaneously, although the greatest distance achieved in flight
and the smallest value of the lateral deviation between the ball and the touchline, or the least flight time, is the ideal
situation. This kind of conflicting solution is called a ‘Pareto-optimal solution’. The optimal kick in Pareto-optimal solutions
made by the leg nearest the touchline produces a greater flight distance than the optimal kick in Pareto-optimal solutions
made using the leg furthest from the touchline. The initial pitch angle, which is the angle between the longitudinal axis
of the ball and the horizontal plane, should be comparable to or slightly greater than the initial flight path angle in order
to satisfy the Pareto-optimal solutions. 相似文献
13.
Simon Choppin 《Sports Engineering》2013,16(3):189-194
As a bluff object, a football experiences high aerodynamic drag when flow is laminar due to early boundary layer separation and a large low-pressure region. The length and depth of a football’s seams can influence the separation point by triggering a turbulent boundary layer at lower Reynolds numbers. Football manufacturers can control a football’s behaviour through careful design and material choice. However, assessing the aerodynamic performance of a football can be a lengthy and expensive process, traditionally requiring the use of a suitable wind tunnel. Measuring the drag force at varying Reynolds numbers gives a full aerodynamic profile which determines how the ball will behave during flight. Some studies have attempted to establish the aerodynamic properties of footballs using recorded trajectories, but these only ascertained average properties rather than a full aerodynamic profile. This paper describes a method which uses a series of recorded trajectories to calculate the full aerodynamic properties of a football. To assess the accuracy and robustness of this method, simulated trajectory data were used to which varying degrees of noise and aerodynamic lift were added. The assessment found that random noise does not affect the accuracy of the methodology significantly. At larger magnitudes, random aerodynamic lift makes the methodology ineffective (equivalent to ball spin >100 rpm). Future work will concentrate on assessing the effectiveness of the methodology using ball trajectories recorded using 3D high-speed video techniques. 相似文献
14.
In this study, the flight performance of four models of shuttlecocks, two with feather skirts and two with plastic, is investigated. The aerodynamic forces of each shuttlecock at varying air speed and angle of attack are measured in a subsonic wind tunnel. Empirical correlations derived from these data are then incorporated into an adaptive, shuttlecock-specific numerical trajectory simulation. These simulated trajectories are in good agreement with experimental results, with average and maximum errors of 2.5 and 9.1% in vertical distance travelled. The aerodynamically adaptive trajectory model is used to analyse four common types of badminton shot: serve, net, smash and high clear. From these simulations, it is found that the trajectory paths of the higher quality plastic shuttlecock most closely mimic those of the feather shuttlecock of same speed grade. Results of both aerodynamic testing and trajectory simulation provide quantitative support for players?? preference for the ??feel?? and responsiveness of feather shuttlecocks. It is also observed that plastic shuttlecocks fly faster than do feather shuttlecocks under smash shots, a behaviour explained by a reduction of drag due to skirt deformation observed in wind tunnel experiments at high flight velocity. The results of the study highlight the influence of shuttlecock design and material on shuttlecock flight. 相似文献
15.
This paper describes the results of a numerical study to determine the optimal flight technique for V-style ski jumping. We
attempt to answer the question of how a jumper should fly in order to increase their flight distance in a V-style posture.
The index of performance in this optimization study is the horizontal flight distance, which is mathematically equivalent
to the total flight distance, and the control parameters are the ski-operning angle and the angle of forward lean that the
jumper employs (the body-ski angle). The flight trajectory is simulated on the basis of an aerodynamic database constructed
from wind tunnel test data. It is found that the ski-opening angle should be increased in the first half of the flight, and
then maintained at a constant value during the rest of the jump. Optimal control of the ski-opening angle when there is either
a headwind or tailwind is also discussed. It is found that the jumper needs to control the skiopening angle over a wider range
in the case of a headwind than in the case of a tailwind. The jumper's skill in controlling the ski-opening angle is very
important for increasing the flight distance, especially in the case of a tailwind. 相似文献
16.
Wu T Gervais P 《Sports biomechanics / International Society of Biomechanics in Sports》2008,7(1):88-99
Many slo-pitch coaches and players believe that generating spin on a ball can affect its trajectory. The influence of air resistance on a ball that is thrown at a moderate speed and spin is unclear. The aim of this study was to examine the influence of spin on the ball's trajectory in slo-pitch pitching using both experimental results and ball flight simulations. Fourteen pitchers participated in the study, each of whom threw five backspin and topspin pitches each. Data were collected using standard three-dimensional videography. The horizontal velocity, vertical velocity, angular velocity, release height, and horizontal displacement of the backspin pitches were significantly higher than those of the topspin pitches. The ball flight simulations were developed to examine the influence of the ball spin, and it was concluded that the spin of the ball had a significant effect on the ball's vertical and horizontal displacements. Furthermore, our results suggest that a backspin pitch that reaches the maximum height allowable and lands in the front edge of the strike zone has the steepest slope. The present results add to our understanding of projectile motion and aerodynamics. 相似文献
17.
乒乓球的旋转与速度存在着相对关系,是乒乓球技术中的普遍规律。在论证中提出了相对速度与球心速度之比作为特征准数,将点的运动轨迹分为三类,分别为“螺旋线”“波纹线”和“旋轮线”。从而将复杂的乒乓球技术划分为“旋转型”“速度型”和“综合型”三种基本类型。运动员击球的点在第二轨迹不同的位置上合成速度不相等。因此,运动员在第二轨迹的不同阶段击球手感旋转不相同,而且该点的合成速度矢量决守乒乓球技术的打法特征。根据高吊弧圈球与前冲弧圈球的特征准数不同,说明了运动员对这两种球型接球手感旋转不同的原因。 相似文献
18.
Direction of spin axis and spin rate of the pitched baseball 总被引：1，自引：0，他引：1
Jinji T Sakurai S 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(2):197-214
In this study, we aimed to determine the direction of the spin axis and the spin rate of pitched baseballs and to estimate the associated aerodynamic forces. In addition, the effects of the spin axis direction and spin rate on the trajectory of a pitched baseball were evaluated. The trajectories of baseballs pitched by both a pitcher and a pitching machine were recorded using four synchronized video cameras (60 Hz) and were analyzed using direct linear transform (DLT) procedures. A polynomial function using the least squares method was used to derive the time-displacement relationship of the ball coordinates during flight for each pitch. The baseball was filmed immediately after ball release using a high-speed video camera (250 Hz), and the direction of the spin axis and the spin rate (omega) were calculated based on the positional changes of the marks on the ball. The lift coefficient was correlated closely with omegasinalpha (r = 0.860), where alpha is the angle between the spin axis and the pitching direction. The term omegasinalpha represents the vertical component of the velocity vector. The lift force, which is a result of the Magnus effect occurring because of the rotation of the ball, acts perpendicularly to the axis of rotation. The Magnus effect was found to be greatest when the angular and translational velocity vectors were perpendicular to each other, and the break of the pitched baseball became smaller as the angle between these vectors approached 0 degrees. Balls delivered from a pitching machine broke more than actual pitcher's balls. It is necessary to consider the differences when we use pitching machines in batting practice. 相似文献
19.
In time trial cycling stage, aerodynamic properties of cyclists are one of the main factors that determine performances. Such
aerodynamic properties are strongly dependent on the cyclist ability to get into the most suitable posture to have minimal
projected frontal area facing the air. The accurate knowledge of the projected frontal area (A) is thus of interest to understand the performance better. This study aims for the first time at a model estimating accurately
A as a function of anthropometric properties, postural variations of the cyclist and the helmet characteristics. From experiments
carried out in a wind tunnel test-section, drag force measurements, 3D motion analysis and frontal view of the cyclists are
performed. Computerized planimetry measurements of A are then matched with factors related to the cyclist posture and the helmet inclination and length. Data show that A can be fully represented by a rate of the cyclist body height, his body mass, inclination and length of his helmet. All the
above-mentioned factors are thus taken into account in the present modelling and the prediction accuracy is then determined
by comparisons between planimetry measurements and A values estimated using the model. 相似文献
20.
This study involved a theoretical and an experimental investigation of the direct free kick in soccer. Our aim was to develop a mathematical model of the ball's flight incorporating aerodynamic lift and drag forces to explore this important 'set-play'. Trajectories derived from the model have been compared with those obtained from detailed video analysis of experimental kicks. Representative values for the drag and lift coefficients have been obtained, together with the implied orientation of the ball's spin axis in flight. The drag coefficient varied from 0.25 to 0.30 and the lift coefficient from 0.23 to 0.29. These values, used with a simple model of a defensive wall, have enabled free kicks to be simulated under realistic conditions, typical of match-play. The results reveal how carefully attackers must engineer the dynamics of a successful kick. For a central free kick some 18.3 m (20 yards) from goal with a conventional wall, and initial speed of 25 m·s?1, the ball's initial elevation must be constrained between 16.5° and 17.5° and the ball kicked with almost perfect sidespin. 相似文献