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Research Papers

Aerodynamics of a Rugby Ball

[+] Author and Article Information
A. J. Vance, J. M. Buick

Department of Mechanical and Design Engineering, Anglesea Road, Anglesea Building,  The University of Portsmouth, Portsmouth PO1 3DJ, United Kingdom

J. Livesey

 Defence College of Aeronautical Engineering (Gosport), in partnership with VT Flagship, Royal Naval Air Engineering and Survival School, HMS Sultan, Gosport PO12 3BY, United Kingdom

J. Appl. Mech 79(2), 021020 (Feb 24, 2012) (5 pages) doi:10.1115/1.4005562 History: Received February 15, 2011; Accepted October 26, 2011; Posted January 31, 2012; Published February 16, 2012; Online February 24, 2012

This paper describes the aerodynamic forces on a rugby ball traveling at speeds between 5 and 15 ms−1 . This range is typical of the ball speed during passing play and a range of kicking events during a game of rugby, and complements existing data for higher velocities. At the highest speeds considered here, the lift and drag coefficients are found to be compatible with previous studies at higher velocities. In contrast to these higher speed investigations, a significant variation is observed in the aerodynamic force over the range of velocities considered. Flow visualizations are also presented, indicating how the flow pattern, which is responsible for the aerodynamic forces, changes with the yaw angle of the ball. This flow and, in particular, the position of the separation points, is examined in detail. The angular position of the separation point is found to vary in a linear manner over much of the surface of the rugby ball; however, this behavior is interrupted when the separation point is close to the ‘tip’ of the ball.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

The measured drag coefficient (open symbols) as a function of the Reynolds number for yaw angles between 0 deg and 60 deg. Also shown are the measured drag coefficient (×) and the literature values [21] for a sphere. The experimental results of Alam (2009) [9] and Seo (2004) [6] are also shown as black and gray filled symbols, respectively.

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Figure 2

The measured lift coefficient (open symbols) as a function of the Reynolds number for yaw angles between 10 deg and 60 deg. The experimental results of Alam [9] and Seo [6] are also shown as black and gray filled symbols, respectively.

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Figure 3

The lift to drag ratio L/D as a function of the yaw angle, α

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Figure 4

Smoke visualizations of the air flow around the rugby ball at yaw angles of (a) 0 deg, (b) 10 deg, (c) 20 deg, (d ) 30 deg, (e) 40 deg, (f ) 50 deg, (g) 60 deg, (h) 70 deg, (i ) 80 deg, and ( j ) 90 deg

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Figure 5

The positions of the separation point at the top θ and the bottom φ of the ball with respect to the longitudinal axis of the ball (subscript b) and the air direction (subscript a). The solid lines indicate the best-fit straight lines through selected points and the dashed line is 180 deg minus the yaw angle, representing the position of the ‘back’ tip of the ball, tip Y, with respect to the incoming air flow.

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Figure 6

The position of the upper and lower separation points and the angles they make with respect to the air flow and the longitudinal axis of the ball. Tips X and Y are labeled such that at a yaw angle of 0 deg tip X points directly upwind and tip Y, correspondingly, points downwind.

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