CFD Analysis of Head and Helmet Aerodynamic Drag to Wheelchair Racing Pedro Forte Daniel A. Marinho University of Beira Interior Covilhã, Portugal Pedro G. Morouço Polytechnic Institute of Leiria Leiria, Portugal Tiago Barbosa Nanyang Technological University Singapure Abstract—Wheelchair racing, an important event in Paralympics, it requires huge effort from its athletes to overcome the resistive forces. The resistive forces in wheelchair racing are aerodynamic drag and rolling friction. CFD methodology can play a determinant role in aerodynamic analysis. The aim of this study was to analyses the aerodynamic drag at different speeds and attack angles of a human head with a helmet, whilst extrapolating results to better suit the needs of wheelchair racing athletes. Computer Fluid Dynamics methodology was used in this study. A 3D head and helmet scan was obtained from a Paralympics athlete. The 3D model was exported to fluent software generating the aerodynamic drag after numerical simulation. Regardless the velocity, 90º attack angle (subject looking down) presented higher aerodynamic drag (0.732 N) Wheelchair racing athletes should maintain a 0º attack angle (looking forward) mainly at speeds greater than 3.5 m/s. Keywords—CFD; Wheelchair Racing; Aerodynamics; Drag; athlets; I. INTRODUCTION Wheelchair racing is one of the most important events in Paralympics and it holds races from short to long distances (100m to 42km). The athletes are classified in accord to their conditions (T51, T52, T53 and T54 with injuries at C5-6, C7- 8, T1-7 and T8-S4 respectively). [1, 2] The first steps towards wheelchair racing research have occurred in the 1980s based on high speed films at a laboratory [3]. Manufactures estimated that in the 1980s more than 10,000 wheelchair models were produced in the worldwide [4]. Every detail of a race plays an important role on athlete’s performance. The resistance force with an opposite direction is one of the major concerns for the practitioners. If these resistive forces are minimized, it is possible to improve the athlete’s velocity and performance. The resistive forces in wheelchair racing are the rolling friction and the aerodynamic drag [5]. Aerodynamic plays an important role in racing sports, possibly defining the first and second place. At speeds higher than 5m/s, aerodynamic represents roughly 90% of the resistive forces [6-10] being this more determinant in sprinting events. Barbosa at al., [11] showed that at the wheelchair racing world speed record, the air drag may represent 34.89% of the resistive forces. A feasible way to gather insight on this is by computer simulations despite the lacking of research in wheelchair racing [12,13]. Computer fluid dynamics (CFD) methodology has been used to improve athletes’ performance, a better understanding of drag forces allows a development in strategies for equipment improvements towards an enhanced aerodynamics [14]. Despite the equipment’s improvement in minimizing aerodynamic drag, athlete’s posture also plays an important role. A marginal change in the rider’s position can improve up to 10% of aerodynamic drag [15-17]. CFD tools became available in the industrial market by the 1990s [18]. CFD presents a good match between the numerical simulations and experimental testing. A 3D model is required for the simulation. The model could be obtained with a 3D scanner, followed-up by post process of the scans. This can be made in software’s such as Artec Studio 0.7 (Artec, USA), Geomagic (3D Systems, USA) and Maya (Autodesk Inc.,USA). The edited scans are exported to Ansys (Ansys Ins., USA) for greed generation and definition of elements in 3D areas [5]. The aim of this study was to compare by CFD methodology the differences between two head and helmet positions, at 0º and 90º angle of attack. II. METHODS A. Model A wheelchair racing Paralympics athlete’s head and track helmet were scanned by a 3D Artec Scanner (Artec Group, Inc.). The Paralympics was ranked fourth world in 100 and 400 meters’ competitions in the T-52 category at the time of this research. The scans were obtained with the subject in a seated position looking forward and performed in the different plans and views allowing a full head scan without holes. This process was conducted by Artec Studio 0.7 (Artec, USA)