Aerodynamic analysis of single jersey knitted fabrics with slub yarn influence on air drag behavior

Abstract Enhancing the aerodynamic properties of sports fabric is crucial for achieving optimal athletic performance in high-speed competitions. This research examines the aerodynamics of single jersey knitted sports textiles made with combed cotton yarns, focusing on fabric extension, porosity, and surface air drag effects. Samples were produced on a circular knitting machine with varying stitch densities, yarn structures (including slub yarns), and loop forms. A specially designed wind tunnel measured drag forces on knitted fabric samples draped over a cylindrical form, simulating real airflow conditions. Surface morphology describes the overall loop arrangement and three-dimensional structure of the knitted fabric, while surface texture refers to micro-level roughness caused by yarn heterogeneity, such as slub yarns. The term “customized fabric construction” refers to intentionally modifying stitch density, loop length, and yarn type (including uniform and slub yarns) to evaluate their effects on aerodynamic properties. Wind tunnel tests showed that stretching fabric in the course direction increased drag force by up to 28% compared to wale direction stretching, due to greater looping deformation and pore size expansion. Fabrics with slub yarns displayed 15–20% higher drag coefficients at Reynolds numbers below 10,000, attributed to increased surface roughness and turbulence. Empirical equations predicting drag forces based on Reynolds number, porosity, and surface area were developed, achieving an R² value of 0.92 when regressed against experimental data.The findings highlight the importance of using high stitch density, uniform yarn constructions, and a smooth fabric surface to reduce aerodynamic drag in sports fabrics. The research offers valuable recommendations for designing knitted fabrics with better aerodynamic performance. The novelty of this study is experimentally demonstrating, for the first time, the combined effect of fabric stretch direction and slub yarn morphology on the aerodynamic drag of knitted sports fabrics, supported by a predictive drag coefficient model.