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1.
数学计算的结果如果在所有冲角下,阻力和升力系数,俯仰和横滚力矩和铁饼旋转的阻滞转矩都有可靠的测量数据的话,如果八个初始条件已知——这八个初始条件是:铁饼初始的旋转速率和方向矢量(三个变量);初始投出速度(如果投掷的方位沿着X轴则有两个变量);脱手高度(一个变量)和风速(如果假设只有水平方向的风,有两个高量),——那末就有可能编成计算机程序,来计算铁饼的轨道。实际上,对于研究来说,为了得到这八个变量的最佳配合,这个方法是不切实际的,特别是因为旋转力矩尚未有测量过由于这个原因,为了简化计算,必须作出一系列的简化假设。此外,在所有的计算中,已经假设了 相似文献
2.
《西安体育学院学报》2014,(1):121-128
运用文献资料调研、录像解析、比较分析与数理统计等方法,对第32届世界跳伞锦标赛女子定点跳伞比赛的前8名运动员低空操纵技术特征进行分析。结果表明:(1)低空操纵技术随着风速的变化而变化。静风天和12 m风速采用的修正技术较多,32 m风速采用的修正技术较多,35 m风速多采用双手同时压棒技术,55 m风速多采用双手同时压棒技术,57 m风速采用小动量的修正技术。(2)五边飞行的时间控制在147 m风速采用小动量的修正技术。(2)五边飞行的时间控制在1416 s之间较适宜。(3)低空修正频率随着风速的改变而改变。316 s之间较适宜。(3)低空修正频率随着风速的改变而改变。35 m风速修正次数在45 m风速修正次数在46次,静风天和1-2 m风速修正次数86次,静风天和1-2 m风速修正次数810次,510次,57 m风速修正的次数多为10次以上。影响跳伞运动员低空操纵技术的主要因素有空中航线的设计能力、不同的风速风向运动员五边的控伞时间、个人控伞能力、修正偏差的频率。 相似文献
3.
470级帆船是奥运会双人操控的帆船级别,为了优化船体与稳向板操控策略,利用数值模拟方法开展了470级帆船船体与稳向板相互影响时船体系统的水动力性能特性研究,得到了阻力随航速(2 m/s、4 m/s、6 m/s、8 m/s、10 m/s)变化的规律,数值模拟控制方程为RANS方程和连续方程,模拟中采用RNG eke-湍流模型。研究发现:稳向板和船体水动力会相互影响,两者配合时阻力特性相比单独时发生改变;不同航速下对水动力影响程度不相同,在较低航速时,稳向板对船体阻力影响程度较明显;航速越高船体对稳向板的阻力影响程度越大。因此,稳向板对470级帆船船体阻力的影响不可忽略;由于470级帆船是双人操控,在比赛过程中运动员可以根据实际需要适当调节稳向板,减小船体总阻力从而改变船体的航速,提高比赛成绩。 相似文献
4.
田径规则规定当风速超过2m/s时,创造的世界纪录不予认可,因此体育场设计过程中应重视外部环境对体育场内场风的影响.造成体育场内场风速变化的影响因素较多,其中建筑物的结构形式是一个很重要的影响因素.本文选取某市奥体中心体育场建筑施工图原图建模,运用数字化手段对挑棚样式进行优化,采用数值模拟的方法对不同挑棚样式对体育场内场风的影响进行了研究,得出了不同挑蓬样式的内场风风等值线图和速度矢量图,显示了内场风场的变化,提出了风影响预报,为体育场设计及使用过程中引入环境风分析提供了依据. 相似文献
5.
目的:讨论一种在赛艇训练中增加训练阻力同时又不影响运动员技术动作的设备,即赛艇阻力器,在不同攻角、不同速度状态下,阻力、压力的变化,阻力与速度之间的关系以及增阻效果分析。方法:运用CFD软件FLUENT 6.2版本进行数值模拟。结果:速度不同,攻角相同状态下的阻力系数是相等的,阻力随速度和攻角的增大而增大,速度变化对阻力板阻力及压力的影响要大于角度的变化所产生的影响,阻力大小与速度的平方成正比,而阻力系数是常数。以155kg和175kg赛艇,阻力板攻角90°,赛艇划行速度5m/s为例,当无风状态时,安装阻力板的155kg赛艇增加的阻力(20.58N)比增加20kg重量(175kg)的阻力值(7.25N)大13.33N,增加的阻力值接近2倍。当顺风风速为3m/s时,阻力板增加的阻力为3.26N,比增加20kg重量的阻力值小3.99N,当逆风风速为3m/s时,阻力板增加的阻力为51.94N,比增加20kg重量增加的阻力值大44.69N,增加的阻力值近6倍多。结论:FLUENT软件对赛艇阻力板阻力计算是准确的,模拟的结果可以应用于具体的实际问题中。90°攻角状态下使用阻力板增加的阻力要优于由于赛艇艇重增加所达到的增阻效果。当处于顺风训练时,风速使阻力板增加的阻力值减小,减弱增阻效果,而逆风训练时,风速使阻力板产生的阻力值增大,加大了增阻效果。因此,采用阻力板训练,可以不改变赛艇的吃水和重心,保证运动员技术的完整性和连贯性,并且增加训练的强度,提高了训练的科学化水平。 相似文献
6.
关于男子低重心标枪出手条件的分析 总被引：2，自引：0，他引：2
在标枪风洞测力实验基础上,建立标枪飞行数理模型进行计算机优化,得到了有规律的结论,结合投掷实践分析了标枪出手适宜条件。出手初速在25m/s～30m/s的范围内,最佳出手条件是:投掷角为40°,迎角为-11°。就投掷成绩而言,负攻角比零攻角好,零攻角又比正攻角好。低重心标枪俯仰力矩值比旧标枪大,低重心标枪出手条件不好,投掷成绩下降幅度比旧标枪大。一般情况下投掷角不能小,攻角绝对值不能大,这样相应成绩更好些。投掷标枪不能沿纵轴用力,也不可能沿纵轴用力。标枪以不为零的攻角出手是获得空气动力效率的充分必要条件。 相似文献
7.
目的得到航速对于470级帆船船体的阻力大小影响的系列规律,增加运动员对帆船船体水动力性能认识,更加高效操纵帆船。方法利用计算流体动力学方法,湍流模式采用RNG k-ε湍流模型,运用SIMPLE算法进行求解,空间离散格式采用二阶迎风格式,边界条件均设置为速度入口、压力出口,数值模拟了速度为2 m/s、4 m/s、6 m/s、8 m/s、10 m/s等5种工况下帆船船体水动力性能,分析不同航速条件下船体的阻力和压力分布。结果船体受到的阻力随航速的增大而增大,在阻力增大趋势线中低航速条件下阻力变化斜率较小、高航速条件下阻力斜率较大。根据趋势线确定阻力与航速的乘幂公式,可以预测不同航速条件下船体在不考虑兴波条件下的船体所受到的阻力大小。研究中不同航速对船体压力分布的规律基本一致,造成的影响主要体现在船体不同部位受力的值上,不同航速对船体船首局部压力造成的影响差异很大。船体考虑兴波时压力分布规律影响差异较大,在不考虑兴波时航速对船体压力分布规律影响较小。结论航速对于船体的阻力大小影响较大,船体阻力随航速的增大而增大;船体阻力随航速变化可以用乘幂公式拟合;船体的兴波对船体阻力分布规律影响不可忽略。 相似文献
8.
9.
《西安体育学院学报》2017,(5):520-525
体育馆室内合理热环境既要满足人体需求,也是满足合理地使用与节约能源的需要。利用CFD技术对大型体育馆气流组织进行模拟和预测,得到体育馆室内空气的速度、温度等物理量分布情况。研究发现:处于送风口双重影响区域的位置风速较大,影响观众的热舒适性;体育馆比赛区域上方四周环绕式送风形成的速度场分布均匀,处于0~0.5 m/s之间,可满足比赛要求;四周环绕送风方式可在入场观众较少时通过安排观众集中就坐,达到节能减排的目的。空调机组对体育馆室内热环境营造研究结果将为体育场馆非均匀热环境研究打下基础,为体育馆节能措施提供理论支持。 相似文献
10.
本文运用文献资料法、二位录像简析法、数理统计法、对比分析法等研究方法,以第18届俄勒冈田径世锦赛男子百米冠军Fred Kerley关键技术环节运动学特征为研究对象,全面分析和掌握Fred Kerley在世锦赛男子100米比赛中的关键运动技术表现特征,以期揭示世界级百米运动员的竞技特征,为提升我国短跑整体水平、了解该项目的竞技规律提供参考。研究结果：(1)在选取Kerley四场比赛中,步频指数达到8.50成绩便突破9.80s,两次破9.80s的比赛均是如此。对于身材高大的运动员都是提高步频来寻求成绩上的突破,我国优秀百米运动员亦是如此,并不能盲目追求步长来提高成绩。(2)在纵向对比运动员成绩时,风速因素也可考虑进去。世锦赛百米决赛如果风速在顺风0.9m/s的有利情况下,Kerley百米成绩甚至可以达到9.73s-9.74s。(3)Kerley百米跑步频指数与Bolt已极为接近,以稳定步频略微提升步长为主要练习方向,追求步长指数也趋于“博尔特化”,有望突破百米最佳成绩。(4)Kerley最大速度能力已达到世界顶级水平,百米全程最大速度出现在47-55.5米之间,为12.687m/s,最大速... 相似文献
11.
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
12.
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
13.
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
14.
Fluid forces on kayak paddle blades of different design 总被引：1，自引：1，他引：0
Three kayak paddle blades of different design (Conventional, Norwegian, Turbo) were tested in a low-speed wind tunnel at a
maximum chord Reynolds number of Re = 2.2–2.7 × 105 (corresponding to speed through water of ≈1 m/s). The mean drag force and side force acting on each blade were measured,
as the yaw and pitch angles were varied. The results were compared with those recorded for a finite rectangular flat plate
of similar area and aspect ratio. For zero pitch angle of the blades, the results indicate that the drag coefficient was mostly
independent of the blade design as the yaw angle was varied between ± 20°, with only the Norwegian blade design displaying
a marginally higher drag coefficient than either of the other two blades or the flat plate. Increasing the pitch angle to
30°, while maintaining the yaw angle at zero, resulted in a 23% reduction of the drag coefficient for the flat plate, but
only a 15% reduction of the drag coefficients for the three blades. For all designs, the drag coefficient reduction followed
a simple cosine relationship as the pitch angle or yaw angle was increased. The wind tunnel experiments revealed that the
side force coefficients for all three paddle blade designs were entirely independent of the blade design and were indistinguishable
from those recorded for a flat plate. In summary, the study showed that the nondimensional force coefficients are largely
independent of the paddle blade design. 相似文献
15.
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
16.
Aerodynamic efficiency is one of the important criteria for racing bicycle helmets, especially in time trial event. The physical characteristics of a bicycle helmet especially its venting geometry, position and number of vents play a crucial role in the aerodynamic efficiency of the helmet. Despite the importance of this, little information on aerodynamic behaviour of racing bicycle helmets is available. In this study, a series of commercially available time trial helmets were investigated in a wind tunnel environment over a range of wind speeds, and yaw and pitch angles to understand their aerodynamic behaviour. In order to obtain as realistic a data as possible, an instrumented mannequin was used in the wind tunnel testing. The experimental findings indicate that the aerodynamic performance of current production time trial helmets varies significantly. The results also show that helmet length as well as vent geometry and vent area have significant effects on aerodynamic drag of a time trial helmet. A time trial helmet having longer length and smooth vents with minimum vent area can reduce aerodynamic drag significantly. 相似文献
17.
Measurements are presented of drag and lift on new tennis balls in flight. Two video cameras were used to measure the velocity and height of the balls at two positions separated horizontally by 6.4 m. The balls were fired from a ball launcher at speeds between 15 and 30 m/s and with topspin or backspin at rates up to 2,500 rpm. Significant shot-to-shot variations were found in both the drag and lift coefficients. The average drag coefficient was 0.507 ± 0.024, independent of ball speed or spin, and lower than the value usually observed in wind tunnel experiments. The lift coefficient increased with ball spin, on average, but significant lift was observed even at very low spin. The latter effect can be attributed to a side force arising from asymmetries in the ball surface, analogous to the side force responsible for the erratic path of a knuckleball in baseball. 相似文献
18.
Modelling the flight of a soccer ball in a direct free kick 总被引：2，自引：0，他引：2
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 x s(-1), the ball's initial elevation must be constrained between 16.5 degrees and 17.5 degrees and the ball kicked with almost perfect sidespin. 相似文献
19.
Mikko Virmavirta Juha Kivekäs 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):358-369
The special wind compensation system recently adopted by Fédération Internationale de Ski (FIS; International Ski Federation) to consider the effects of changing wind conditions has caused some controversy. Here, the effect of wind on jumping distance in ski jumping was studied by means of computer simulation and compared with the wind compensation factors used by FIS during the World Cup season 2009/2010. The results showed clearly that the effect of increasing head/tail wind on jumping distance is not linear: +17.4 m/ ? 29.1 m, respectively, for a wind speed of 3 m/s. The linear formula used in the trial period of the wind compensation system was found to be appropriate only for a limited range of jumping distances as the gradient of the landing slope slows down the rate of distance change in long jumps. 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