Effect of seam characteristics on critical Reynolds number in footballs

Abstract

In recent years, the design of footballs, including the number and shape of the panels forming the surface of footballs, has undergone a significant change. However, panels of varied shapes and seams are combined in complex ways to form the surface shape of footballs, and almost nothing is known about the effect of these surface shapes on the football drag characteristics. The present study used a wind tunnel to study the relationship between the critical Reynolds number and the length, depth, and width of the panel joints (seams) of 10 most recent football types used in matches in recent years. The results show the tendency that the drag coefficient in the super-critical regime (30 m/s) of a football increases as the panel joint length increases. Moreover, the depth of the panel joint indicates the highest correlation with the critical Reynolds number (r = -0.71, p < 0.01) and is considered to be a strong and convenient indicator that expresses the roughness (large scale) of the football surface. This study reveals the drag characteristics of the latest footballs and enables some degrees of prediction of the critical Reynolds number for the latest football types and those that will be developed in the future.

Effect of a soccer ball’s seam geometry on its aerodynamics and trajectory

“…30 A slightly stronger correlation between critical Reynolds number and seam depth has been seen in other work on soccer balls. 32 The work presented in this article not only extends that previous research, it greatly expands the look at how a wide range of trajectories are influenced by the aerodynamic coefficients. Having teased out how a ball's aerodynamic properties are influenced by panel texturing and seam geometry, the authors of this work will focus on spinning balls next.…”

“…A strong correlation between critical Reynolds number and seam depth has been seen in other work on soccer balls. 32 That work used three balls, different from those used in this study, and that work not only had significantly less trajectory modeling than the present study, it had an error in the equations of motion the authors solved. The work presented in this article not only extends that previous research, it greatly expands the look at how a wide range of trajectories are influenced by the aerodynamic coefficients.…”

On the Aerodynamic Forces on a Baseball, With Applications

“…Data shown in Frohlich [22] and Cross [23] fit to such model. On the other hand, from the famous curve of Adair [7] to the recent data obtained by Naito [24], most of the experimental measures suggest a model without drag crisis [6,17,25,26]. This predominance maintains for other sphere balls [23,[27][28][29] and gives rise to most of the used models to compute the drag force without including the drag crisis phenomenon.…”

Serve Ball Trajectory Characteristics of Different Volleyballs and Their Causes

“…This decrease in the drag coefficient due to the change in flow is called drag crisis, and it plays an important role in volleyball because the ball decelerates in flight to a speed range where the drag crisis occurs [11][12][13][14]. The fluid force characteristics of a ball vary depending on the type of ball and the panel surface [15][16][17][18][19][20][21][22][23][24][25][26][27]. Measurements using a wind tunnel showed that the drag coefficient, the magnitude of lateral force, and the speed range at which drag crisis occurs differs depending on the type of ball and the panel surface.…”