Aerodynamic Dimpling and Surface Roughness of a Textile Metamaterial

The aerodynamic performance of textiles is vital in high-speed wearable applications, where air flow around the body is directly influenced by the fixed surface roughness of the textile microstructure. However, these surface properties are typically optimized for a single wind speed, overlooking dynamic velocity profiles and environmental changes. Here, we present a structured textile with tunable surface roughness, enabled by a novel stretch-induced dimpling mechanism. The auxetic textile structure exhibits dimpling even when tightly fitted to the surface of an object, allowing surface roughness to be controlled by a linear stretch. Finite Element Method (FEM) unit-cell simulations are employed to identify optimal dimpling heights for specific wind-speed applications. Wind-tunnel testing is used to characterize these tunable aerodynamic properties, that can modulate aerodynamic drag by up to 20%. These dynamic wind-tunnel experiments further demonstrate the textile's ability to adapt and maintain minimal drag force even under varying wind speeds, allowing us to realize a new generation of applied aerodynamic metamaterials.