An experimental aerodynamic study of a series of rugby balls

The aerodynamic properties of oval shaped balls, rugby balls and Australian Rules (AFL) football, exhibit peculiar trends which impacts sharply on the balls flight trajectory; with a kicking efficiency of only 60% amongst elite footballers in AFL and NRL, understanding the physics behind oval shaped balls can be very perplexing. Very little literature has been made available on the aerodynamic characterisitics of oval shaped balls, under non-spinning conditions. THe rugby and AFL footballs are asymmetric by design, and hence can rotate both laterally and longitudinally, not to mention an offset angle to these axes of rotation. Initial tests of three differing rugby balls, positioned at a zero pitch angle but with a varying yaw angle have been analysed with curious results. Subsequently, a look into the flow around these balls was studied using flow visualisation methods of wool tuft and smoke flow

An experimental and computational study of a rugby ball's aerodynamics

As the Australian Rules football and the rugby ball have an odd ellipsoidal shape, they tend to differ greatly from conventional spheroid shaped sports balls in both the aerodynamic behaviour they exhibit and the axes in which they rotate. Copious amounts of data can be retrieved on spherical shpaed ball; scarce information is readily available on elliptical balls on the public domain. To be able to fully grasp an understanding on these elliptical shaped balls, exhaustive experimental studies have been undertaken for a range of varying speeds and yaw angles. The airflow around Rugby and Australian Rules foot balls was visualized and the average drag coefficients for both balls were determined and compared. The average drag coefficient for all the speeds and yaw angles was computed and compared; subsequently the corresponding Reynolds numbers variations at yaw angles were analysed; with a comparison of data analysed obtained from CFD and EFD

A review of power generation from wind in Australia

With recent surge in fossil fuel prices, demands for cleaner renewable energy sources, wind turbines have become a viable technology for power generation. Greenhouse gases such as carbon dioxide emitted into our atmosphere have resulted on what many scientists believe is due to climate change. To tackle climate change, many of the world's developed countries have agreed on a policy to cute down on its carbon emission. Australia has agreed on a renewable energy target of 20 per cent by the year 2020. Twenty per cent of Australia's energy generation must come from renewable energy sources by this period. This paper will examine the importance wind energy as an alternative source of energy to fossil fuel based energy both globally and locally. Wind energy is fastest growing renewable energy in the world. It has the potential to rival the cost competitiveness of conventional energy sources. Wind energy is a reliable and sustainable with a mature technology and a proven track record

Effects of seam and surface texture on tennis balls aerodynamics

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

A study of aerodynamic drag of American footballs

American football is one of the most popular sports in North America. It is enjoyed both by participants and spectators. The centre piece of the games is the oval shaped ball. The flight trajectory of an American football largely depends on its aerodynamic characteristics. Despite the popularity of the game, it appears that scant information on the aerodynamic force experienced by an American football is available in the open literature. Although attempts were made to construct the flight trajectory of the ball, without knowing the aerodynamic drag coefficient, it is hard to build such a model. The shape of an American football is similar to that of an ellipsoid. It has more pointed ends and rough surfaces. The ball used in college level teams possesses a pair of seams at the pointed ends. This makes the airflow around the ball even more complex. The primary purpose of this study is to experimentally measure the aerodynamic forces of American footballs used at professional and college levels under a range of wind speeds and yaw angles. The non-deimensional drag coefficient were estimated and compared. The results indicate that the American footballs possess drag coefficient close to that of other oval shaped balls such as Rugby and Australian rule footballs

Aerodynamics of American footballs under crosswinds

The flight trajectory of an American football largely depends on its aerodynamic characteristics. Despite the popularity of the game, it appears that little information on the aerodynamic force experienced by an American football especially under crosswinds is available in the open literature. The shape of an American football is similar to that of an ellipsoid. It has more pointed ends and has a rough surface. The ball used in college level teams possesses a pair of seams at each of pointed ends. All these features and crosswind make the airflow around the ball more complex. The primary purpose of this study is to experiemental measure the aerodynamic forces of NFL and College Level American footballs under a range of wind speeds and yaw angles (crosswinds). The non-dimensional drag coefficient were estimated and compared. The results indicate that the American footballs possess drag coefficient close to that of other oval shpaed balls such as Rugby and Australian rule footballs. It also shows that the drag coefficient can be almost four times higher under crosswinds