Understanding the Effect of Panel Shape on Soccer Ball Aerodynamics using CFD

Abstract

Football is considered as the most popular sports today and is played widely around the world. Due to increasing technological advancements and demand for better performance, the football manufacturers have been developing new designs progressively since its inception over 110 years ago. A traditional spherical football made of 32 leather panels stitched together in 1970s, has become 14 thermally bonded synthetic curved panels in 2006, 8 thermally bonded panels in 2010 and more recently 6 thermally bounded polyurethane panels in 2014 and innovative six panels design in 2018. The soccer balls having varied panels shape, number, and seam configurations have different aerodynamic behavior and flight characteristics. Unlike other sports balls i.e. golf, cricket and tennis etc., very few research studies have attempted to examine the aerodynamics characteristics of the different soccer balls. Most of the studies conducted in the past in the area of soccer ball aerodynamics are of experimental nature and involved measurement of the forces such as drag and lift using wind tunnel testing. To the best of our knowledge, very little research has been performed on simulating the flow around different soccer balls having specific panel shape using computational fluid dynamic (CFD) techniques. The CFD analysis will allow an effective estimation of fully turbulent around the different soccer balls. The aim of this research is to understand the effect of panel shape on soccer ball aerodynamics using computational fluid dynamics techniques. The whole study is divided into two phases. In the first phase, the turbulent air flow around a static sphere is investigated numerically for a range of Reynolds numbers using finite volume method based commercial software ANSYS® Fluent. In order to choose a suitable turbulence modeling approach, the results obtained from LES are compared with computations from BSLRSM. In the later phase, the turbulence modeling approach found adequate for predicting the complex flow field features around the smooth sphere, is used for simulating the flow around the two soccer balls (Adidas Telstar 18 and Brazuca) having six number of panels and panel shape as well as different seam viii configuration. So the simulations are performed at the different incoming flow velocities ranging from 7m/s to 35m/s. It was observed that RANS based turbulence modeling approach can be used for simulating the flow around a sphere in the laminar flow regime (𝑅𝑒≤104). However, for higher Reynolds number (𝑅𝑒>104), LES is a more appropriate choice. Both Brazuca and Telstar 18 have approximately the same critical speed. Telstar 18 has a smaller drag coefficient than that of Brazuca in the narrow speed range. Nevertheless, Telstar 18 mostly has slightly larger drag coefficients. In case of Brazuca, he boundary layer separation take place around 98o, however, in case of Telstar-18 the separation angle is around 101o. 8. It is observed that the effect of the panel shape and seam configuration are more significant on the flow field around the soccer balls as compared to soccer ball drag coefficient.