The effect of textile air permeability on the drag of high-speed winter sports apparel

In a number of sport disciplines characterized by high velocities, aerodynamic performance of sports apparel is a concern. The goal is often to reduce the aerodynamic drag force and thereby increase speed. In the design of optimized competition apparel the fabric properties will be very important. One fabric property which has traditionally been considered an influencing parameter on aerodynamic performance is the air permeability. In this paper the effect of air-permeability, treated as an independent variable, upon aerodynamic drag on a bluff body is investigated. Similar multilayer textiles with internal membranes regulating air permeability were tested on cylindrical models in wind tunnel experiments in order to identify a possible relation between air-permeability and drag force. A weak dependence of flow transition on air-permeability could be found, but this could be considered to have a limited effect on the aerodynamic performance of sports garments.