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1.
Abstract The purpose of this investigation was to examine the fluid dynamic characteristics of the two most commonly used oar blades: the Big Blade and the Macon. Scaled models of each blade, as well as a flat Big Blade, were tested in a water flume using a quasi-static method similar to that used in swimming and kayaking research. Measurement of the normal and tangential blade forces enabled lift and drag forces generated by the oar blades to be calculated over the full range of sweep angles observed during a rowing stroke. Lift and drag force coefficients were then calculated and compared between blades. The results showed that the Big Blade and Macon oar blades exhibited very similar characteristics. Hydraulic blade efficiency was not therefore found to be the reason for claims that the Big Blade could elicit a 2% improvement in performance over the Macon. The Big Blade was also shown to have similar characteristics to the flat plate when the angle of attack was below 90°, despite significant increases in the lift coefficient when the angle of attack increased above 90°. This result suggests that the Big Blade design may not be completely optimized over the whole stroke. 相似文献
2.
The purpose of this investigation was to examine the fluid dynamic characteristics of the two most commonly used oar blades: the Big Blade and the Macon. Scaled models of each blade, as well as a flat Big Blade, were tested in a water flume using a quasi-static method similar to that used in swimming and kayaking research. Measurement of the normal and tangential blade forces enabled lift and drag forces generated by the oar blades to be calculated over the full range of sweep angles observed during a rowing stroke. Lift and drag force coefficients were then calculated and compared between blades. The results showed that the Big Blade and Macon oar blades exhibited very similar characteristics. Hydraulic blade efficiency was not therefore found to be the reason for claims that the Big Blade could elicit a 2% improvement in performance over the Macon. The Big Blade was also shown to have similar characteristics to the flat plate when the angle of attack was below 90 degrees , despite significant increases in the lift coefficient when the angle of attack increased above 90 degrees . This result suggests that the Big Blade design may not be completely optimized over the whole stroke. 相似文献
3.
Abstract Our aim was to present a mathematical model of rowing and sculling that allowed for a comparison of oar blade designs. The relative movement between the oar blades and water during the drive phase of the stroke was modelled, and the lift and drag forces generated by this complex interaction were determined. The model was driven by the oar shaft angular velocity about the oarlock in the horizontal plane, and was shown to be valid against measured on-water mean steady-state shell velocity for both a heavyweight men's eight and a lightweight men's single scull. Measured lift and drag force coefficients previously presented by the authors were used as inputs to the model, whichs allowed for the influence of oar blade design on rowing performance to be determined. The commonly used Big Blade, which is curved, and it's flat equivalent were compared, and blade curvature was shown to generate a 1.14% improvement in mean boat velocity, or a 17.1-m lead over 1500 m. With races being won and lost by much smaller margins than this, blade curvature would appear to play a significant role in propulsion. 相似文献
4.
Abstract The aim of the present study was to find a more optimal blade design for rowing performance than the Big Blade, which has been shown to be less than optimal for propulsion. As well as the Big Blade, a flat Big Blade, a flat rectangular blade, and a rectangular blade with the same curvature and projected area as the Big Blade were tested in a water flume to determine their fluid dynamic characteristics at the full range of angles at which the oar blade might present itself to the water. Similarities were observed between the flat Big Blade and rectangular blades. However, the curved rectangular blade generated significantly more lift in the angle range 0 – 90° than the curved Big Blade, although it was similar between 90 and 180°. This difference was attributed to the shape of the upper and lower edges of the blade and their influence on the fluid flow around the blade. Although the influence of oar blade design on boat speed was not investigated here, the significant increases in fluid force coefficients for the curved rectangular blade suggest that this new oar blade design could elicit a practically significant improvement in rowing performance. 相似文献
5.
Our aim was to present a mathematical model of rowing and sculling that allowed for a comparison of oar blade designs. The relative movement between the oar blades and water during the drive phase of the stroke was modelled, and the lift and drag forces generated by this complex interaction were determined. The model was driven by the oar shaft angular velocity about the oarlock in the horizontal plane, and was shown to be valid against measured on-water mean steady-state shell velocity for both a heavyweight men's eight and a lightweight men's single scull. Measured lift and drag force coefficients previously presented by the authors were used as inputs to the model, whichs allowed for the influence of oar blade design on rowing performance to be determined. The commonly used Big Blade, which is curved, and it's flat equivalent were compared, and blade curvature was shown to generate a 1.14% improvement in mean boat velocity, or a 17.1-m lead over 1500 m. With races being won and lost by much smaller margins than this, blade curvature would appear to play a significant role in propulsion. 相似文献
6.
Pascal Hémon 《Sports Engineering》2018,21(3):189-197
We present a study of the hydrodynamic characteristics of sea kayak paddles without taking into account the kayaker. We focus on traditional paddles used in the Arctic, one from Greenland and one from the Aleutian Islands. A basic modern European paddle is included in the study for comparison. First the paddle stroke parameters specific to sea kayaking are identified because previous studies were devoted to a competition context. The hydrodynamic force generated by the blade motion is detailed: two terms are identified, one involving the inertia of the water surrounding the blade at the beginning of its motion, and the second term is the classical drag/lift force. Drag and lift force coefficients were measured in a wind tunnel. The data allow computation of the hydrodynamic force during a paddle stroke. The European paddle was shown to be more efficient than the traditional paddles because of its shorter length to width ratio which contributed to a larger inertia effect. However, the force obtained with the traditional paddles better follows the imposed motion by the kayaker so that they are more comfortable and less tiring in the context of long distance trips, as those practiced in sea kayaking. 相似文献
7.
Abstract In ice hockey, skating performance depends on the skill and physical conditioning of the players and on the characteristics of their equipment. CT Edge have recently designed a new skate blade that angles outward near the bottom of the blade. The objective of this study was to compare the frictional characteristics of three CT Edge blades (with blade angles of 4°, 6°, and 8°, respectively) with the frictional characteristics of a standard skate blade. The friction coefficients of the blades were determined by measuring the deceleration of an aluminium test sled equipped with three test blades. The measurements were conducted with an initial sled speed of 1.8 m · s?1 and with a load of 53 kg on each blade. The friction coefficient of the standard blades was 0.0071 (s=0.0005). For the CT Edge blades with blade angles of 4°, 6°, and 8°, friction coefficients were lower by about 13%, 21%, and 22%, respectively. Furthermore, the friction coefficients decreased with increasing load. The results of this study show that widely accepted paradigms such as “thinner blades cause less friction” need to be revisited. New blade designs might also be able to reduce friction in speed skating, figure skating, bobsledding, and luge. 相似文献
8.
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
9.
Badminton synthetic shuttlecocks are known to have significantly different aerodynamic behaviours compared to feathered shuttlecocks due to the difference in designs and use of materials. Given the fragility of avian feathers used for feathered shuttlecocks and the constantly increasing cost of purchase, the interest to assess the current synthetic shuttlecock design as a feasible alternative has re-emerged. The single-piece injection-moulded synthetic shuttlecock has been the mainstream design for the past 50 years; however, little evidence has supported that the design mimics the aerodynamics of feathered shuttlecocks. Recently, a two-part skirt design has emerged proclaiming to have surpassed its synthetic predecessor in regard to matching the aerodynamics of feathered shuttlecocks. In the current study, two different synthetic designs (injection-moulded vs two-part skirt) were benchmarked against a feathered shuttlecock. A wind tunnel test was conducted between 30 and 145 km/h. The drag coefficients of both synthetic shuttlecocks were similar to the feathered shuttlecock up to 105 km/h. Thereafter, the drag coefficient of the injection-moulded design dropped from 0.62 to 0.5 and showing no signs of levelling at speeds over 105 km/h, while the coefficient for two-part skirt design stabilised at approximately 0.55. It was concluded that the two-part skirt design better mimicked the aerodynamics of the feathered shuttlecock. 相似文献
10.
The aim of the present study was to find a more optimal blade design for rowing performance than the Big Blade, which has been shown to be less than optimal for propulsion. As well as the Big Blade, a flat Big Blade, a flat rectangular blade, and a rectangular blade with the same curvature and projected area as the Big Blade were tested in a water flume to determine their fluid dynamic characteristics at the full range of angles at which the oar blade might present itself to the water. Similarities were observed between the flat Big Blade and rectangular blades. However, the curved rectangular blade generated significantly more lift in the angle range 0-90 degrees than the curved Big Blade, although it was similar between 90 and 180 degrees. This difference was attributed to the shape of the upper and lower edges of the blade and their influence on the fluid flow around the blade. Although the influence of oar blade design on boat speed was not investigated here, the significant increases in fluid force coefficients for the curved rectangular blade suggest that this new oar blade design could elicit a practically significant improvement in rowing performance. 相似文献
11.
Ice friction of flared ice hockey skate blades 总被引：2，自引：0，他引：2
In ice hockey, skating performance depends on the skill and physical conditioning of the players and on the characteristics of their equipment. CT Edge have recently designed a new skate blade that angles outward near the bottom of the blade. The objective of this study was to compare the frictional characteristics of three CT Edge blades (with blade angles of 4 degrees, 60, and 8 degrees, respectively) with the frictional characteristics of a standard skate blade. The friction coefficients of the blades were determined by measuring the deceleration of an aluminium test sled equipped with three test blades. The measurements were conducted with an initial sled speed of 1.8 m s(-1) and with a load of 53 kg on each blade. The friction coefficient of the standard blades was 0.0071 (s = 0.0005). For the CT Edge blades with blade angles of 4 degrees, 6 degrees, and 8 degrees, friction coefficients were lower by about 13%, 21%, and 22%, respectively. Furthermore, the friction coefficients decreased with increasing load. The results of this study show that widely accepted paradigms such as "thinner blades cause less friction" need to be revisited. New blade designs might also be able to reduce friction in speed skating, figure skating, bobsledding, and luge. 相似文献
12.
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
13.
Pascual Marqués-Bruna 《Sports Engineering》2011,13(4):195-204
This study examined aerodynamic properties and boundary layer stability in five cambered airfoils operating at the low Reynolds
numbers encountered in motor racing. Numerical modelling was carried out in the flow regime characterised by Reynolds numbers
0.82–1.29 × 106. The design Reynolds number of 3 × 106 was used as a reference. Aerodynamics variables were computed using AeroFoil 2.2 software, which uses the vortex panel method
and integral boundary layer equations. Validation of AeroFoil 2.2 software showed very good agreement between calculated aerodynamic
coefficients and wind tunnel experimental data. Drag polars, lift/drag ratio, pitching moment coefficient, chordwise distributions
(surface velocity ratio, pressure coefficient and boundary layer thickness), stagnation point, and boundary layer transition
and separation were obtained at angles of attack from −4° to 12°. The NASA NLF(1)-0414F airfoil offers versatility for motor
racing with a wide low-drag bucket, low minimum profile drag, high lift/drag ratio, laminar flow up to 0.7 chord, rapid concave
pressure recovery, high resultant pressure coefficient and stall resistance at low Reynolds numbers. The findings have implications
for the design of race car wings. 相似文献
14.
The speed attained by a track cyclist is strongly influenced by aerodynamic drag, being the major retarding force in track events of more than 200 m. The aims of this study were to determine the effect of changes in shoulder and torso angles on the aerodynamic drag and power output of a track cyclist. The drag of three competitive track cyclists was measured in a wind tunnel at 40 kph. Changes in shoulder and torso angles were made using a custom adjustable handlebar setup. The power output was measured for each position using an SRM Power Meter. The power required by each athlete to maintain a specific speed in each position was calculated, which enabled the surplus power in each position to be determined. The results showed that torso angle influenced the drag area and shoulder angle influenced the power output, and that a low torso angle and middle shoulder angle optimised the surplus power. However, the lowest possible torso angle was not always the best position. Although differences between individual riders was seen, there was a strong correlation between torso angle and drag area. 相似文献
15.
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
16.
目的:探讨环境风对跳台滑雪空中飞行气动特性的影响。方法:通过计算流体力学(computational fluid dynamics,CFD)方法数值模拟预测了不同环境风下跳台滑雪空中飞行空气动力学特性,并探究了水平方向环境风、竖直方向环境风以及侧向环境风对气动特性的影响。将跳台滑雪运动员与滑雪板看成一个多体系统,建立在空中飞行某一种普遍姿态下此多体系统的精细化三维几何模型与网格模型,采用部分时均(partially averaged Navier-Stokes,PANS)湍流模型进行数值模拟,提取多体系统的受力及力矩情况,直观地显示多体系统周围的流场信息。数值预测涉及的水平方向风风速包括-4 m/s、-2.5 m/s、-1 m/s、0 m/s、1 m/s、2.5 m/s、4 m/s等工况;竖直方向风风速包括-8 m/s、-4 m/s、-2.5 m/s、-1 m/s、0 m/s、1 m/s、2.5 m/s、4 m/s、8 m/s等工况;侧向风风速包括1.5 m/s、3.0 m/s、4.5 m/s、7.5 m/s、10.5 m/s、13.5 m/s等工况。结果:1)水平方向环境风下多体系统升力、阻力以及俯仰力矩变化明显,与风速呈现近似线性关系,同时水平逆风情况下力学特性数值结果的增长速度大于水平顺风情况下力学特性数值结果的减小速度;2)在竖直方向风速较小时(小于2.5 m/s),升力、阻力以及俯仰力矩增加缓慢,在竖直方向风速较大时(大于4 m/s),升力、阻力以及俯仰力矩开始相对快速增加,同时,竖直向上环境风使得升力、阻力、俯仰力矩增大,竖直向下环境风使得升力、阻力以及俯仰力矩减小,而且竖直向上环境风情况下增长幅度明显小于竖直向下环境风情况下减少幅度;3)侧向环境风产生偏航力、偏航力矩、翻滚力矩,同时,侧向环境风对运动员的升力、阻力以及俯仰力矩产生影响。在风速较小(小于3 m/s)时,这些力和力矩很小,在风速较大(大于4.5 m/s)时,比较明显。结论:1)水平方向环境风对跳台滑雪空中飞行气动特性的影响非常明显,相较而言,竖直方向环境风和侧向环境风对空中飞行气动特性的影响小很多,但侧向环境风的影响情况较为复杂,对多体系统产生较为明显的偏航力、偏航力矩、翻滚力矩;2)环境风对跳台滑雪空中飞行气动特性的影响机理能够为比赛临场预判与决策提供有效的辅助支持,也为运动员空中飞行稳定性控制与技术训练提供科学指导。 相似文献
17.
The highly unsteady flow around a rowing blade in motion is examined using a three-dimensional computational fluid dynamics
(CFD) model which accounts for the interaction of the blade with the free surface of the water. The model is validated using
previous experimental results for quarter-scale blades held stationary near the surface in a water flume. Steady-state drag
and lift coefficients from the quarter-scale blade flume simulation are compared to those from a simulation of the more realistic
case of a full-scale blade in open water. The model is then modified to accommodate blade motion by simulating the unsteady
motion of the rowing shell moving through the water, and the sweep of the oar blade with respect to the shell. Qualitatively,
the motion of the free surface around the blade during a stroke shows a realistic agreement with the actual deformation encountered
during rowing. Drag and lift coefficients calculated for the blade during a stroke show that the transient hydrodynamic behaviour
of the blade in motion differs substantially from the stationary case. 相似文献
18.
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
19.
Abstract In rowing, power is inevitably lost as kinetic energy is imparted to the water during push-off with the blades. Power loss is estimated from reconstructed blade kinetics and kinematics. Traditionally, it is assumed that the oar is completely rigid and that force acts strictly perpendicular to the blade. The aim of the present study was to evaluate how reconstructed blade kinematics, kinetics, and average power loss are affected by these assumptions. A calibration experiment with instrumented oars and oarlocks was performed to establish relations between measured signals and oar deformation and blade force. Next, an on-water experiment was performed with a single female world-class rower rowing at constant racing pace in an instrumented scull. Blade kinematics, kinetics, and power loss under different assumptions (rigid versus deformable oars; absence or presence of a blade force component parallel to the oar) were reconstructed. Estimated power losses at the blades are 18% higher when parallel blade force is incorporated. Incorporating oar deformation affects reconstructed blade kinematics and instantaneous power loss, but has no effect on estimation of power losses at the blades. Assumptions on oar deformation and blade force direction have implications for the reconstructed blade kinetics and kinematics. Neglecting parallel blade forces leads to a substantial underestimation of power losses at the blades. 相似文献
20.
Nicholas P. Linthorne James E. Cooper 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):175-185
This study investigated the effect of the coefficient of friction of a running surface on an athlete's sprint time in a sled-towing exercise. The coefficients of friction of four common sports surfaces (a synthetic athletics track, a natural grass rugby pitch, a 3G football pitch, and an artificial grass hockey pitch) were determined from the force required to tow a weighted sled across the surface. Timing gates were then used to measure the 30-m sprint time for six rugby players when towing a sled of varied weight across the surfaces. There were substantial differences between the coefficients of friction for the four surfaces (μ = 0.21–0.58), and in the sled-towing exercise the athlete's 30-m sprint time increased linearly with increasing sled weight. The hockey pitch (which had the lowest coefficient of friction) produced a substantially lower rate of increase in 30-m sprint time, but there were no significant differences between the other surfaces. The results indicate that although an athlete's sprint time in a sled-towing exercise is affected by the coefficient of friction of the surface, the relationship relationship between the athlete's rate of increase in 30-m sprint time and the coefficient of friction is more complex than expected. 相似文献