著者

伊藤 慎一郎 加瀬 光輝

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2013 (ISSN:24242896)

巻号頁・発行日

pp._G1104-01_-_G1104-03_, 2013-11-09 (Released:2017-06-19)

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A flying disc can fly through the air because of the combination of the lift and drag forces by the oncoming air flow. Actual fight conditions were confirmed to perform the wind tunnel experiment beforehand. In order to clarify the mechanism of flight of flying discs, the flow field structure and the fluid force were investigated on non-spinning and spinning conditions. In the fluid force measurement, lift and drag forces were taken by varying wind speeds, spin speeds, and angle of attack. Drag and lift forces were found to increase as spin increased. The angle of attack on the maximum range of lift-drag ratio or glide ratio was found to be wide from 6 to 13 degrees which was suitable for a long distance throwing. Using a smoke wind tunnel, flow visualization around the disc was performed in order to understand the effect of disc spin. It was found that spin enhances lift force by attracting the Coanda effect on the trailing edge.

著者

伊藤 慎一郎

出版者

バイオメカニズム学会

雑誌

バイオメカニズム学会誌 (ISSN:02850885)

巻号頁・発行日

vol.34, no.3, pp.203-206, 2010 (Released:2016-04-15)

参考文献数

1

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水棲生物を系統樹から形態学的に分類すると彼らの遊泳運動メカニズムが大まかに分類できてくる.さらに生活形態を見ると運動形態が自ずと定まってくる.彼らの運動メカニズムは大きく揚力推進メカニズムと抗力推進メカニズムとに二分できる.前者は恒常的に遊泳するもの,後者は逆に常日頃は不活発であるが,非常時には瞬発力を発揮できるものである.生活形態が中心となって,自然淘汰によって生活に関わるエネルギーが最小になるように運動モードが決定しているようである.本解説ではそれぞれのメカニズムを述べると共に,さらに分類できるものは具体例を挙げて詳細な運動メカニズムを述べている.

著者

多田 海斗 平塚 将起 伊藤 慎一郎 瀬尾 和哉

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.89, no.924, pp.23-00045, 2023 (Released:2023-08-25)

参考文献数

15

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The paper describes the critical Reynolds number of soccer balls as a function of the total groove volume on the ball surface. In this study, the aerodynamic drag and separation point of 6 soccer balls with different panel orientations were measured in a wind tunnel. Moreover, the total volume of grooves on the ball’s surface was measured by One shot 3D measuring machine. It was found that the drag coefficient in the supercritical region and the critical Reynolds number depend on the design of the ball surface (shape, number of panels, surface roughness). A negative correlation exists between the total groove volume on the surface and the critical Reynolds number. When the total groove volume is large, the drag in the supercritical region increases. The position of the separation point does not change in the subcritical and supercritical regions even if the orientation of the panel is changed. However, when the groove width is wider, the panel orientation dependence becomes significant in the supercritical region. In the transition region, the position of the separation point differs depending on the panel's orientation.

著者

伊藤 慎一郎

出版者

一般社団法人日本機械学会

雑誌

ジョイント・シンポジウム講演論文集 : スポーツ工学シンポジウム : シンポジウム:ヒューマン・ダイナミックス : symposium on sports engineering : symposium on human dynamics

巻号頁・発行日

vol.2008, pp.181-184, 2008-11-05

被引用文献数

2

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25 world records were born in the swimming races of the 2008 Olympic Games in Beijing. The swimmer's wear rate of Lazer Racer, a drag reduction swim suit, among the gold medalists was 94%. The effectiveness of the swimsuit was quite apparent The reason of the drag reduction was to reduce the surface viscous friction drag and to reduce the projection cross-sectional area due to its compression effectiveness. Before Beijing Olympic started, expecting new records by these gold medalists with LZR Racer were calculated by dividing a race into two phases, a start & turn phase and a steady propulsive phase, on the assumption that theses gold medalists had the same swimming techniques of the previous world record holders. Although the drag reduction rate used in this calculation was modified according to one of the manufacturer announcement, each expecting new records was an approximate value of the new world records in Beijing Olympics. It was found that the speed increase effect by the swimsuit

著者

伊藤 慎一郎

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.73, no.734, pp.1975-1980, 2007-10-25 (Released:2011-03-03)

参考文献数

7

被引用文献数

2 8

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A slipstream is a region of reduced pressure or even suction (negative pressure) formed behind an object in downstream. Even in a marathon event, it is possible to use preceding runners as a shield to reduce aerodynamic drag and to carry out physical strength presservation. These preceding runners are called pacemakers, who maintain a lap time of an main runner. In this research, to confirm the effect of pacemakers' slipstream and to find a suitable arrangement of pacemakers, drag of the main runner was measured using 3 component load cells in a wind tunnel. And the factor of drag reduction was studied by grasping the flow field using a smoke tunnel. Numerical calculations were also carried out in a real Reynolds number and compared with experiments concerning drag and flow field.

著者

伊藤 慎一郎 三谷 曜子 佐藤 克文 内藤 靖彦

出版者

日本流体力学会

雑誌

日本流体力学会年会講演論文集 (ISSN:13428004)

巻号頁・発行日

vol.2006, 2006-09-05

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The authors found that bodies of seals had natural oscillation in pitching and rolling motions in drift dive phase by data loggers. The phenomenon is periodically oscillated at a low frequency not by flippering movement. Model experiments were performed in a circulating water channel and in a wind tunnel. The result shows clearly that the oscillatory motion of the bodies of seals during the drift dive was caused by flow induced vibration.

著者

中島 知浩 伊藤 慎一郎 平塚 将起

出版者

一般社団法人 日本機械学会

雑誌

シンポジウム: スポーツ・アンド・ヒューマン・ダイナミクス講演論文集 2017 (ISSN:24329509)

巻号頁・発行日

pp.B-12, 2017 (Released:2018-05-25)

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The structure of the current tennis ball is covered with a uniform felt fabric on the outer surface made of hard rubber. The inside of the ball is filled with air about 1.8 atm. The seam is filled with adhesive or resin. The seams are filled with glue or resin. The ball in tennis is always struck with rotation. Rotational speed of the serve ball is about 5,500 rpm maximum. It is up to about 4,700 rpm for the stroke. As the ball continues to hit, the surface felt wears. Also, air leaks out through the structure inside. These factors cause a difference in the aerodynamic characteristics of new and used balls.In general it is a new ball to use in the game, but the one used in practice is a used ball. Worn out changes the hydrodynamic properties of the ball, and the trajectory of the ball also changes. Therefore, the performance difference between the new tennis ball and the used tennis ball should be confirmed by measuring the fluid force.In this research, the aerodynamic characteristics of the old and new tennis balls rotating were investigated and the PIV results of the flow around the ball due to the wear of the felt producing these characteristics. For the four types of tennis balls tested, used balls showed higher in drag coefficient than new balls, and new balls tended to be higher than used ball in lift coefficient. It is believed that deformation due to deterioration of ball rubber brings about a change in drag coefficient, which causes a change in lift coefficient due to wear of the surface felt. In the new ball, feltfluff stands, which indicates that the wake flow is large and inclined diagonally backward compared to the used ball, and the air around the ball is found to be caught by the felt fluff.

著者

伊藤 慎一郎 鎌田 真輝 浅井 武 瀬尾 和哉

出版者

一般社団法人 日本機械学会

雑誌

シンポジウム: スポーツ・アンド・ヒューマン・ダイナミクス講演論文集

巻号頁・発行日

vol.2011, pp.23-26, 2011

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The configuration of soccer balls has closely approached a perfect round shape by not only reducing a number of panels but also by eliminating roughness of the panel joints by thermal bonding process recently. Therefore, in a non-rotating or low-rotating moving shot, a soccer ball drops and curves by the change of wake flow, which is called a knuckle ball effect. It is said that the cause of the swerving ball on no rotating shoot of the soccer ball depends on the outbreak of the vortex occurred in the wake. However, it is not grasped the timing among the vortex outbreak and the swerving of balls. In this study, the velocity fluctuation of the ball wake was measured with hot wire probe and the oscillation of the ball was measured with three components load cell. And also the asymmetric configuration of the ball panel against moving direction was investigated as a factor to bring unexpected change of the ball orbit. The results show that the position change of the tail of vortex ring affects the swerving of the balls and that the low-rotating ball changes its face against the moving direction and it produces irregular lateral force.