A study of spin effects on tennis ball aerodynamics

The aerodynamic behaviour of a tennis ball is very complex and significantly differs from other sports balls due to its surface structures (fuzz, seam orientation etc). Relatively high rotational speeds (spin) make the aerodynamic properties of tennis balls even more complex. Although several studies have been conducted on drag and lift in steady state condition (no spin involved) by the author and others, little or no studies have been conducted on spin effects. The so called Magnus effect on a sphere is well known in fluid mechanics. It is believed that the spinning can affect aerodynamic drag and lift of a tennis ball thus the motion and flight path of the ball. Therefore, the primary objectives of this work are to study the spin effects using both experimental and computational methods. In order to achieve these objectives, a series of tennis balls were used to measure their aerodynamics forces as a function of wind speeds, seam orientation and spins. The experimental study was conducted in the RMIT Industrial Wind Tunnel. A computational study of a simplified tennis ball was also studied using commercial software 'FLUENT'. The CFD results were compared with the experimental findings. Flow around the ball was visualised with smoke.

The Journal of Engineering and Exact Sciences

In this study, tennis balls were analyzed experimentally through the use of a wind tunnel with speed ranging from 1m/s to 14 m/s, which is a variation in the Reynolds number (10,000 < Re < 60,000). In this context, aerodynamic aspects of the balls were evaluated, including the position of the seam and the degree fuzz, i.e., with and without fuzz. It was possible to analyze the effect of drag on the diameter, in the investigation of the relationship between the drag coefficient (CD) and the Reynolds number (Re) for new and used balls. Graphics were generated using the Reynolds number and the Drag Coefficient in order to assess the (non) dependency of these parameters. In the measurements performed, the static balls inside the wind tunnel were considered, i.e., without rotation. Therefore, no discussions about the Magnus force are presented. The results obtained, ? 3 to ? 0.60, were consistent for the range of the Reynolds number investigated. High values are expected for the ...

Procedia Engineering, 2012

Currently, serving becomes a dominant factor in tennis tournament as the ball travels faster and sometimes the returning player and spectators are unable to follow the track of the ball. As a result, the game becomes boring causing the spectator to lose passion for the game. The reduced speed of the ball can make the game more enjoyable. The understanding of aerodynamic behaviour of tennis balls is important in helping to design and develop a ball that can slow down the game. The complex surface texture of a tennis ball may affect its aerodynamic behaviour as well. As limited information on aerodynamic behaviour of contemporary tennis balls are available, a study was undertaken to investigate the effects of seam and surface texture of a range of commercially manufactured tennis balls. The drag coefficients were analysed and compared. The surface texture and seam orientation showed a noticeable variation in drag coefficients among these balls.

2012

The purpose of this study was to examine the function of spin on shot trajectory during flight in table tennis. Using film images of an actual match, we computed the 3D coordinates of a ball to analyze the shot trajectories. The theoretical spin-free (TSF) ball trajectories, obtained using a similar approach to Jinji and Sakurai (2006), were compared with the observed shot trajectories. For drive shots, the shot length in the TSF ball was significantly longer than in the observed shots. However, for push shots, among the 30 shots analyzed, 17 of the TSF balls traveled a shorter distance than the observed shots, though difference between them was found not to be significant. The work done by Magnus effect on the ball was estimated by the amount of deflection in vertical direction during flight.

The Engineering of Sport 7, 2008

The ability to understand and predict the flight trajectory of a sports ball is important in many fields of sports engineering. The aerodynamic coefficients of sports balls have been studied in detail and yet aerodynamic models generally assume that spin rates are constant during flight. This study examines the spin decay of sports balls in flight in order to improve the accuracy of aerodynamic models. Several types of sports ball (tennis ball, worn tennis ball, football, oversize tennis ball) were launched in a sports hall using artificial bowlers at various speeds and spin rates. The start and end of the trajectories were filmed using two high speed video cameras and the resulting measurements were used to assess the spin decay of each ball as well as the factors affecting spin decay. The data shows a strong linear relationship between spin decay and the product of initial spin and speed for all the different sports balls tested. However, the constant in this linear relationship was found to be different for each of the different balls and was assumed to be dependent on the physical attributes of the different balls. Dimensionless parameters were derived such that the differences between the sports ball spin characteristics could be more easily identified. It was found that the rate of spin decay is largely dependent on the balls moment of inertia; however, its surface roughness and its boundary layer flow regime are also of importance.

Procedia Engineering, 2014

Ball spin plays an important role in the modern game of tennis. Previous work has shown that reducing the number of cross strings in a tennis racket can increase rebound ball spin. The aim of this study was to further our understanding of the effect of the number of cross strings on ball spin generation. Two rackets were tested, one with 16 main and 19 cross strings and the other with 16 main and 12 cross strings. The racket frame was fully-constrained and a ball was fired onto the strings at inbound angles of 24 and 38º. Inbound velocity was set at 30 m/s and inbound spin was varied from 0 to 500 rad/s. Ball velocity and spin, and lateral main string deflections during impact, were measured from high-speed video footage. Lateral string deflections were consistently larger for the racket with fewer cross strings. The racket with fewer cross strings produced slightly higher rebound spin and lower horizontal rebound velocity, which was attributed to the main strings returning during the restitution phase of the impact.

The aerodynamic behaviour of the golf ball is primarily dependent on the physical features of complex dimples. The dimples vary in sizes, shapes and depths which generate complex aerodynamic flow pattern around the ball. Although some studies have been conducted on golf ball aerodynamics, the aerodynamic behaviour of dimple characteristics is not fully understood. The primary objective of this research is to experimentally evaluate the aerodynamic properties (drag, lift/down force) of a series of commercially available golf balls. Each of these new balls has different dimple characteristics. These balls were tested under a range of speeds. The aerodynamic properties were analysed. Due to varied dimple geometry, the magnitudes of drag coefficients of these balls were varied significantly. The non-dimensional drag coefficient for each ball was compared. The effects of spin on drag and lift have also been evaluated. However, spin data was not included in this paper.

Sports Engineering, 2013

Topspin has become a vital component of modern day tennis. Ball-to-string bed and inter-string friction coefficients can affect topspin generation from a racket. The aim of this research was to determine the effect of string bed pattern on topspin generation. Tennis balls were projected onto nine head-clamped rackets with different string bed patterns. The balls were fired at 24 m/s, at an angle of 26°to the string bed normal with a backspin rate of 218 rad/s and outbound velocity, spin and angle were measured. Outbound velocity was shown to be independent of string bed pattern. Outbound angle increased with the number of cross strings, while outbound topspin decreased. In the most extreme case, decreasing the number of cross strings from 19 to 13 increased rebound topspin from 117 to 170 rad/s.

Proceedings of the ISCIE International Symposium on Stochastic Systems Theory and its Applications

The aerodynamic behavior of a tennis ball is completely different from other sports balls due to the size and the ball surface structure. The tennis ball goes through three distinct stages during the normal shot. These stages are racket/ball impact, trajectory through the air and then the ball/surface impact. The main objective of this research is to investigate experimentally and numerically the trajectories of a ball hit 38.9 m/s at various angles. Also the study is focused on the effect of the drag force and the turbulence around the ball. In the numerical analysis, the computational fluid dynamic CFD code, FLUENT for 2D and 3D configurations has been employed. The use of the numerical tool has resulted in a detailed investigation of the forces which act on the ball, aerodynamic forces to facilitate the ball and the ball rebound.

In this paper, we firstly analyze the effects of the rebounds and aerodynamics for trajectory of a table tennis ball. We firstly analyze the effect of the aerodynamics with a criterion of evaluation, where the half area of the table is considered as 9 divided areas. Furthermore, the drag and lift coefficients are identified by assuming that the rotational velocity is invalid during the ball flying. With the identified coefficients, the modeling errors of the table and racket are secondly verified by the criterion mentioned previously. Some conclusions are finally shown.