2018 Volume 3 Pages 118-122
The aerodynamic characteristics of sports suits play a crucial role in helping professional athletes gain a competitive edge in their chosen sport. The fluid forces acting on the body of the sports competitor are influenced by the surface topology of the fabric, position and size of the seams, use of fasteners, and air permeability of the fabric. Wind tunnel experiments and numerical simulations provide deep insight on the aerodynamic characteristics of sports suit designs. Ski jumping is a sport in which the competitor is judged based on the flight form and flight distance; therefore, ski jumpers attempt to fly as far as possible upon take-off. The fabric used for ski jumping suits plays a crucial role in achieving favorable aerodynamic characteristics. According to the rules and regulations for ski jumping competitions, the outstretched fabric should have a minimum air permeability of 40 L/m2/s at a water pressure of 98 Pa (10 mmAq). To date, little is known regarding the effects of air permeability on the aerodynamic characteristics of ski jumping suits, which forms the motivation of this study. The purpose of this study is to investigate the effect of air permeability on the aerodynamic characteristics of ski jumping suits. Wind tunnel experiments were carried out on an elliptic cylinder clothed with ski jumping suit fabrics of different air permeability. The aerodynamic forces acting on the fabric-clothed elliptic cylinder were measured using a three-component force balance. The velocity profiles were also measured to examine the effect of air permeability on the flow around the fabric-clothed elliptic cylinder. The experimental results show that the drag forces decrease with an increase in air permeability and the stall characteristics are greatly affected by the air permeability. The maximum lift coefficients are lower for fabrics with higher air permeability. However, this is compensated by the occurrence of stall delay for these fabrics and an increase in the lift-to-drag ratio at higher angles of attack. The velocity profiles around the fabric-clothed elliptic cylinder also vary, depending on the air permeability of the fabric.
