Effects of Dimple on Soccer Ball Aerodynamics

Sungchan Hong

and Takeshi Asai

Advanced Research Initiative for Human High Performance (ARIHHP), University of Tsukuba,

1-1-1 Tennoudai, Tsukuba, Japan

Faculty of Health and Sports Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Japan

Keywords: Aerodynamics, Dimple, Soccer Ball.

Abstract: Typically, soccer balls are constructed with 32 pentagonal and hexagonal panels. More recently Teamgeist

and Jabulani balls have 14 and 8 panels, respectively, with dramatically different panel shapes and designs

from conventional balls. The latest model called Beau Jeu, made with 6 panels, has been adopted by many

soccer leagues. However, there are few studies on the aerodynamic characteristics of these balls. This study

examined the trajectory and aerodynamic characteristics of soccer balls constructed with different numbers

and shapes of panels. Results of wind tunnel tests indicated that the aerodynamic forces varied significantly

according to the surface forms. The results showed that the ball trajectory changes according to surface form,

suggesting that surface form has significant effects on the flight of the balls.

1 INTRODUCTION

The pattern of the official ball of the recently

concluded World Cup Soccer is significantly

different from that of the conventional soccer ball

(having 32 pentagonal and hexagonal panels) as

several changes have been made in the design such

as the number of panels making up the ball or its

surface form. Further, it is said that the aerodynamic

force applied on the ball changes depending on the

number of different panels and their orientation,

which in turn changes the trajectory of the ball (Goff

et al., 2014; Hong & Asai, 2014; Hong et al., 2015).

However, the surface form of the soccer ball is a

complex combination of various types of ball panels

and seams and not much is known about the impact

of these surface forms on the aerodynamics of the

ball. Therefore, in the present study, 6 soccer balls,

each with a different number of panels and surface

design (such as the presence or absence of dimples)

were produced and their aerodynamic properties

were studied by wind tunnel experiments.

In addition, the comparison of the official balls

of the 2014 World Cup and the 2016 EURO Cup

that had different kinds of roughness revealed that

even when the balls had the same number and

shapes of panels, the aerodynamic force acting on

the balls varied greatly depending on the surface

form of the of the ball. Besides making clear the

aerodynamic characteristics of the latest soccer ball,

the present study also shows that it is possible to

predict, to some extent, the flight trajectory of the

soccer balls that will be developed in future.

2 METHODS

Wind Tunnel Experiment

The circulating type low speed low turbulence wind

tunnel located in the University of Tsukuba (San

Technologies Co., LTD) (Figure 1) was used in this

experiment. The maximum wind speed was 55 m/s,

blow off size 1.5 m × 1.5 m, wind speed distribution

within ± 0.5%, degree of turbulence less than 0.1 %,

and the blow cage of the measured soccer ball was

within 5% of the blow off size. Using this wind

tunnel, experiments were carried out using 6 types of

balls in all: balls with dimples and without dimples

in each of 32, 12 and 6 panel type of balls.

Figure 1: Set-up wind tunnel test.

Hong, S. and Asai, T.

Effects of Dimple on Soccer Ball Aerodynamics.

In Extended Abstracts (icSPORTS 2016), pages 5-7

The force acting on the soccer ball was measured by

the Sting-type 6-component force detector (LMC-

61256, Nissho Electric Works). The aerodynamic

force measured in this experiment was converted

into the drag coefficient (C

), lift coefficient (C

) and

side force coefficient (C

) as shown in equations (1),

(2) and (3).





=









(1)





 = 









(2)





 = 









(3)

Here, the density of air was taken to be ρ = 1.2

kg/m

, U is the flow velocity and the projected area

of the soccer ball was taken as A = π × 0.112 =

0.038m

3 RESULTS

Figure 2: Change in Cd values for the 6 types of soccer

balls having different surface forms.

Figure 2 shows the drag characteristic curve of the

ball for soccer balls consisting of 32, 12 and 6

panels. From the aerodynamic coefficients of the

balls it is seen that the aerodynamic drag tends to

drop faster in the case of the dimple type soccer

balls than in the case of the no dimple type. Further,

the 32 panel dimple type soccer ball showed the

smallest value of about 0.10 (Re = 2.3 × 10

) for the

supercritical drag coefficient and the 12 panel

dimple type ball showed a value of about 0.15 (Re =

2.1 × 10

). In the case of the no dimple type ball, the

value for the 32 panel ball was about 0.13 (Re = 3.5

× 10

) and for the 12 panel ball it was about 0.12 (Re

= 3.5 × 10

). The 6 panel ball without dimples

showed a value of about 0.12 (Re = 3.4 × 10

Figure 3: Force variation in lift and side forces due to

wind speed (30 m/s).

In a powerful shot at wind speed as high as 30 m/s

(Figure 3), the variation in lift force and side force in

the case of the 32 panel no dimple type ball is 2.5 N

and 2.6 N respectively, while it is 1.3 N and 1.7 N in

the case of the 32 panel dimple type ball. Thus, the

value is smaller for the dimple type than the no

dimple type ball and is believed to provide a

relatively greater sense of stability. Further, the

variation in lift force and side force is smaller for the

12 panel type of ball compared to other types,

showing relatively greater stability.

4 DISCUSSION

First, with regard to the impact of dimples on the

drag of the soccer ball, it was found that the drag

acting on the ball changed depending on the wind

speed interval (Figure 2). In the intermediate speed

interval (10 m/s ~ 20 m/s), the dimple type of soccer

ball has a relatively smaller drag (resistance)

compared with the no dimple type and therefore the

dimple type ball is perceived to be faster. On the

contrary, in the high speed interval (25 m/s ~ 35

m/s) such as while taking a shot, the no dimple type

showed a smaller drag value. Thus it is conceivable

that the dimple type ball flies faster in the

intermediate speed and the no dimple type flies

relatively faster in the high speed interval. Further,

with regard to the impact of dimples on the lift and

side forces of the ball, the dimple type ball was

observed to have relatively less force variation than

the no dimple type (Figure 3). In particular, this

study has made clear the fact that changing the

texture of the ball surface changes the aerodynamic

characteristics of the ball. This suggests that, by

considering the change in aerodynamic

characteristics obtained thus far by modifying the

number and shape of the panels together with the

modification in the surface form, soccer balls with

even more diverse aerodynamic characteristics can

be developed.

icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support

REFERENCES

Goff, J.E., Asai, T. and Hong, S., 2014. A comparison of

Jabulani and Brazuca non-spin aerodynamics.

Proceedings of the Institution of Mechanical

Engineers, Part P: Journal of Sports Engineering and

Technology, 228: 188-194.

Hong, S. and Asai, T., 2014. Effect of panel shape of

soccer ball on its flight characteristics. Scientific

Reports 4: 5068.

Hong, S., Asai, T. and Seo, K., 2015. Visualization of air

flow around soccer ball using a particle image

velocimetry. Scientific Reports 5: 15108.

Effects of Dimple on Soccer Ball Aerodynamics