An aerodynamic analysis of recent FIFA world cup balls

Kiratidis, Adrian L.; Leinweber, Derek B.

doi:10.1088/1361-6404/aaa888

Cited by 9 publications

(11 citation statements)

References 26 publications

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“…This larger total volume of the grooves has affected the drag crisis and drag coefficient. The changes in the drag coefficient of the other balls were consistent with the trends shown in previous studies [8,9,12,[21][22][23]. Thus, the drag coefficient dropped rapidly from about 0.5 to 0.2 in the Reynolds numbers range from 1.0 × 10 5 to 2.4 × 10 5 .…”

Section: Fluid Force Experimentssupporting

confidence: 90%

Effect of Soccer Ball Panels on Aerodynamic Characteristics and Flow in Drag Crisis

2020

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The panel patterns of soccer balls that change with each World Cup have a significant impact on the balls’ aerodynamic and flight characteristics. In this study, the aerodynamic forces of eleven types of soccer ball with different panel patterns were measured in a wind tunnel experiment. We characterized the panel shapes of soccer balls by the length, cross-sectional area, and the panel grooves’ volume. The results confirmed that the drag and drag crisis characteristics are dependent on the groove length and volumes. Flow separation points were visualized by an oil film experiment and particle image velocimetry (PIV) measurement to understand the drag crisis of the soccer balls. The results showed that the panel shape of the ball significantly changes the position of the separation point near the critical region, where the drags crisis occurs. In the critical region, laminar and turbulent flows coexist on the ball. On the other hand, the effect of panel shape on the separation point position is small in subcritical and supercritical states.

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Section: Fluid Force Experimentssupporting

confidence: 90%

Effect of Soccer Ball Panels on Aerodynamic Characteristics and Flow in Drag Crisis

2020

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“…The value of C D in the transition region is in agreement with previous studies on Brazuca, Teamgeist, and Tango12. [19][20][21][22][23][24] This number is very closely linked with the volume of the groove. Figure 8 shows the relation between the Reynolds number of the transition region and the measured volume of the grooves in the balls.…”

Section: Resultsmentioning

confidence: 99%

Stereo three-dimensional particle image velocimetry measurement and aerodynamic force analysis of non-spinning soccer balls

Hiratsuka

Ito

Miyasaka

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part P:

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A knuckle shot, resulting from non-spinning kicking, is an essential technique in soccer. The irregular flight path of the knuckle shot is caused by the aerodynamic force from the three-dimensional twin vortices generated in the wake behind the ball. However, the detailed behavior of the twin vortices and relation between the jet flow and the acting forces on the balls is still not understood. In addition, a more thorough understanding of the effect of ball panels on the formation of twin vortices and jet flow is important to develop balls with high controllability. To study the effect of the ball panel shape on the flight path, stereo three-dimensional particle image velocimetry wake flow measurements and synchronized force measurements were performed on various soccer balls. It was confirmed that the aerodynamic force on the ball is produced by the jet flow generated by the vortices in the wake flow. The directions of the force followed the changes of the jet flow, and the magnitude of the force was strongly associated with the flow rate of the jet. Moreover, the shape of the ball panels, especially the groove volume, determines the critical Reynolds number and the fluttering of the balls.

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“…here, the parameter ∂ is chosen as 2.5 × 10 −4 , and β is 0.83 (Kiratidis and Leinweber, 2018). The spin parameter is S p = rω v , where ω = |ω| and v = |v|.…”

Section: Experimental Model: Aerodynamic Model Of Football With Param...mentioning

confidence: 99%

“…As the whole process contains only one state transition from take-off to end and its action, i.e., the football's initial velocity, is continuous, football flight is an atypical MDP case with continuous action space. Meanwhile, the aerodynamic model of football is strongly non-linear and has no analytical solutions (Myers and Mitchell, 2013 ; Javorova and Ivanov, 2018 ), which involves many complex physical laws (Horowitz and Williamson, 2010 ; Norman and McKeon, 2011 ; Javorova and Ivanov, 2018 ; Kiratidis and Leinweber, 2018 ). It is difficult for the traditional control method to control football flight (Hou and Wang, 2013 ; Hou et al, 2016 ).…”

Section: Introductionmentioning

confidence: 99%

An immediate-return reinforcement learning for the atypical Markov decision processes

et al. 2022

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The atypical Markov decision processes (MDPs) are decision-making for maximizing the immediate returns in only one state transition. Many complex dynamic problems can be regarded as the atypical MDPs, e.g., football trajectory control, approximations of the compound Poincaré maps, and parameter identification. However, existing deep reinforcement learning (RL) algorithms are designed to maximize long-term returns, causing a waste of computing resources when applied in the atypical MDPs. These existing algorithms are also limited by the estimation error of the value function, leading to a poor policy. To solve such limitations, this paper proposes an immediate-return algorithm for the atypical MDPs with continuous action space by designing an unbiased and low variance target Q-value and a simplified network framework. Then, two examples of atypical MDPs considering the uncertainty are presented to illustrate the performance of the proposed algorithm, i.e., passing the football to a moving player and chipping the football over the human wall. Compared with the existing deep RL algorithms, such as deep deterministic policy gradient and proximal policy optimization, the proposed algorithm shows significant advantages in learning efficiency, the effective rate of control, and computing resource usage.

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An aerodynamic analysis of recent FIFA world cup balls

Cited by 9 publications

References 26 publications

Effect of Soccer Ball Panels on Aerodynamic Characteristics and Flow in Drag Crisis

Effect of Soccer Ball Panels on Aerodynamic Characteristics and Flow in Drag Crisis

Stereo three-dimensional particle image velocimetry measurement and aerodynamic force analysis of non-spinning soccer balls

An immediate-return reinforcement learning for the atypical Markov decision processes

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