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1.
2.
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
3.
Chase M. Pfeifer Timothy J. Gay Jeff A. Hawks Shane M. Farritor Judith M. Burnfield 《Sports Engineering》2018,21(2):95-102
A mechanical field-goal kicking machine was used to investigate toppling ball flight in American football place-kicking, eliminating a number of uncontrollable impact variables present with a human kicker. Ball flight trajectories were recorded using a triangulation-based projectile tracking system to account for the football’s 3-dimensional position during flight as well as initial launch conditions. The football flights were described using kinematic equations relating to projectile motion including stagnant air drag and were compared to measured trajectories as well as projectile motion equations that exclude stagnant air drag. Measured football flight range deviations from the non-drag equations of projectile motion corresponded to deficits between 9 and 31%, which is described by a football toppling compound drag coefficient of 0.007 ± 0.003 kg/m. Independent variables including impact location and impact angle orientation resulted in 15 impact conditions. We found that an impact location of 5.5 cm from the bottom of the ball maximized trajectory height and distance. At the 5.5-cm impact location, alterations in impact angle produced minimal change in football trajectory, including launch angle (range = 1.96 deg), launch speed (range = 1.06 m/s), and range (range = 0.94 m). 相似文献
4.
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
5.
Flight dynamics of an American football in a forward pass 总被引：2，自引：2，他引：0
The motion of an American football in a forward pass is discussed in this paper. It was investigated by using wind-tunnel
aerodynamic data in a numerical integration of the full nonlinear equations of motion, and by application of the small-angle
theory for the atmospheric motion of an axisymmetric spinning body. The numerical simulations agree with certain observed
features such as the range, flight duration, and ratio of the spin and precession frequencies. The analytic results reveal
functional dependences of the flight parameters on the aerodynamics and give insights into the physical effects that occur.
Both approaches show a feature that is known as ‘drift’ in the science of ballistics, namely that a long, highly arched trajectory
of a spinning body does not lie in a vertical plane, but rather turns slightly to the left or right, depending on the direction
of the spin vector and on the magnitudes of the aerodynamic loads. 相似文献
6.
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
7.
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
8.
Sasakawa K Sakurai S 《Sports biomechanics / International Society of Biomechanics in Sports》2008,7(3):311-321
Joint angles of the throwing limb were examined from the acceleration phase up until release for the sidearm throwing motion when using a flying disc. 17 individuals (ten skilled, seven unskilled) threw a disc as far as possible ten times. Throwing motions were recorded using three-dimensional high-speed videography. The initial condition of disc release and joint angle kinematics of the upper limb during the throwing motion were obtained. Mean (+/- standard deviation) throwing distance and disc spin rate were significantly greater for skilled throwers (51.4 +/- 6.6 m, 12.9 +/- 1.3 rps) than for unskilled throwers (29.5 +/- 7.6 m, 9.4 +/- 1.3 rps), although there was no significant difference in initial velocity of the disc between the two groups (skilled: 21.7 +/- 1.7m/s; unskilled: 20.7 +/- 2.5m/s). A marked difference in motion of supination/pronation of the forearm before disc release was identified, with the forearm supinated in the final acceleration phase leading up to disc release for the unskilled participants, while the forearm was pronated in the same phase for the skilled participants. These differences in joint kinematics could be related to differences in disc spin rate, and thus led to the substantial differences in throwing distance. 相似文献
9.
A 3D predictive golfer model can be a valuable tool for investigating the golf swing and designing new clubs. A forward dynamic model, which includes a four degree of freedom golfer model, a flexible shaft based on Rayleigh beam theory, an impulse-momentum impact model and a spin rate dependent aerodynamic ball model, is presented. The input torques for the golfer model are provided by parameterized joint torque generators that have been designed to mimic muscle torque production. These joint torques are optimized to create swings and launch conditions that maximize carry distance. The flexible shaft model allows for continuous bending in the transverse directions, axial twisting of the club and variable shaft stiffness as a function of the length. The completed four-part model with the default parameters is used to estimate the ball carry of a golf swing using a particular club. This model will be useful for experimenting with club design parameters to predict their effect on the ball trajectory and carry distance. 相似文献
10.
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
11.
Kei Sasakawa Shinji Sakurai 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):311-321
Joint angles of the throwing limb were examined from the acceleration phase up until release for the sidearm throwing motion when using a flying disc. 17 individuals (ten skilled, seven unskilled) threw a disc as far as possible ten times. Throwing motions were recorded using three-dimensional high-speed videography. The initial condition of disc release and joint angle kinematics of the upper limb during the throwing motion were obtained. Mean ( ± standard deviation) throwing distance and disc spin rate were significantly greater for skilled throwers (51.4 ± 6.6 m, 12.9 ± 1.3 rps) than for unskilled throwers (29.5 ± 7.6 m, 9.4 ± 1.3 rps), although there was no significant difference in initial velocity of the disc between the two groups (skilled: 21.7 ± 1.7 m/s; unskilled: 20.7 ± 2.5 m/s). A marked difference in motion of supination/pronation of the forearm before disc release was identified, with the forearm supinated in the final acceleration phase leading up to disc release for the unskilled participants, while the forearm was pronated in the same phase for the skilled participants. These differences in joint kinematics could be related to differences in disc spin rate, and thus led to the substantial differences in throwing distance. 相似文献
12.
空气作用力对推铅球和跳远成绩的影响 总被引：4，自引：0，他引：4
本文以铅球和跳远为例,计算空气作用力对推铅球和跳远成绩的影响,为寻找减小阻力的方法提供依据。同时,本文的计算公式也可用于其它有类似运动轨迹的体育项目,如链球等 相似文献
13.
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
14.
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
15.
A completely general three-dimensional dynamic model is presented for the motion of basketball shots that may contact the rim, the backboard, the bridge between the rim and board, and possibly the board and the bridge simultaneously. Non-linear ordinary differential equations with six degrees of freedom describe the ball angular velocity and ball centre position. The model includes radial ball compliance and damping and contains five sub-models: purely gravitational flight, and ball-rim, ball-bridge, ball-board, and ball-bridge-board contact. Each contact sub-model has both slipping and non-slipping motions. Switching between the sub-models depends on the reaction force at, and velocity of, the contact point. Although the model can be used to study shots from any point on the court, we here use it to study the sets of free throw release angle, velocity, angular velocity, and lateral deviation angle that result in success (capture), as well as underhand free throws and those using an under-inflated ball. Free throw shots with larger backspin, lower inflation pressures, and underhand release conditions are shown to result in larger capture percentages. 相似文献
16.
A dynamic model for motion of a basketball on the rim is derived. The model is used to investigate shot success sensitivity
to initial conditions and to search for initial conditions that lead to long rim contact times. Nonlinear ordinary differential
equations describe three components of ball angular velocity and contact point position on the toroidal rim. The model includes
radial ball compliance and dissipation and contains three sub-models describing slipping contact, nonslipping contact and
purely gravitational flight. Switching between the three sub-models depends on contact point velocity and friction forces.
Equivalent radial stiffness and damping constants are estimated using experimental ball force-deflection hysteresis data.
General initial conditions almost always involve slip of the ball on the rim. Bouncing on the rim can also occur. After contact
it is possible for the ball to enter the rim with its centre passing significantly below the rim plane before rising and ultimately
escaping. Exotic quasi-equilibrium periodic circular trajectories exist inside but below the rim plane, relying for their
existence on a combination of centripetal force, friction and gyroscopic precession of radial spin about the contact point.
Trajectories, and consequent ball capture or escape, are extremely sensitive to initial conditions, especially rim contact
position and backspin angular velocity. Backspin aids capture on longrolling trajectories. 相似文献
17.
M. C. Jermy A. Burgess C. Feasey M. Lensen C. Willis A. S. Tucker R. W. G. Syme 《Sports Engineering》2014,17(3):151-164
The maximum distance a hammer can be thrown depends on its mass, length and aerodynamic drag, meaning that record hammer throws performed before and after a rule change (for example, if the minimum mass is changed) cannot be compared directly. However, if all factors affecting the flight of a hammer are fully understood, and the range travelled by a hammer thrown with a given initial speed, angle and release height can be predicted, records thrown under different rules can be compared. In this work, a numerical model is developed, which includes the effects of atmospheric pressure, altitude, Coriolis Effect, gravitational variation, wind speed, ambient temperature, linear drag, torsional drag, hammer size and hammer orientation. It is based on the model of Mizera and Horvath (J Biomech 35:785–796, 2002). Two refinements are made: the drag coefficient varies with Reynolds number, and the hammer is represented as a spatially extended object with nonzero moment of inertia. New wind tunnel data on the drag of the three main components of the hammer (ball, cable and handle) are presented. This data are incorporated into the model which is then used to predict throws made at the IAAF 2011 World Athletics Championships (Daegu, Korea). The model is shown to be capable of predicting to within 1 % the distance of hammer throws where the air density, latitude, release height, release angle and release velocity are known. It is more accurate than numeric and analytic models which assume a constant drag coefficient. This may be because it does not require the user to choose the drag coefficient and automatically uses an appropriate drag coefficient regardless of conditions. With a good biomechanical model or good assumptions about release speeds, throws with different implements can be compared to compare records thrown before and after rule changes. Further work is needed to develop a biomechanical model capable of predicting the release speed an athlete can achieve with a range of different implements. 相似文献
18.
The aim of this study was to determine if adults spontaneously exploit the laws of physics to achieve better accuracy when throwing at various distances. Eight adults performed 25 underarm throws at five horizontal circular targets located 4, 5, 6, 7 and 8 m away with a constant 5% relative accuracy requirement. Angle and speed of the ball at release were found to increase with throwing distance, while the coordinates of the release point did not change significantly. These results support the idea that people minimize the variability in impact distance by adapting both the angle and the speed at ball release following a mechanical optimum predicted by the laws of physics. Moreover, variability in distance was found to be less than expected because of independent variations in the angle and speed at ball release. Hence, the control of precision throwing seems to imply compensatory variability, as frequently reported in the control of skilled actions. 相似文献
19.
The aim of this study was to determine if adults spontaneously exploit the laws of physics to achieve better accuracy when throwing at various distances. Eight adults performed 25 underarm throws at five horizontal circular targets located 4, 5, 6, 7 and 8 m away with a constant 5% relative accuracy requirement. Angle and speed of the ball at release were found to increase with throwing distance, while the coordinates of the release point did not change significantly. These results support the idea that people minimize the variability in impact distance by adapting both the angle and the speed at ball release following a mechanical optimum predicted by the laws of physics. Moreover, variability in distance was found to be less than expected because of independent variations in the angle and speed at ball release. Hence, the control of precision throwing seems to imply compensatory variability, as frequently reported in the control of skilled actions. 相似文献
20.
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