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ABSTRACT
Background
Sportswear aerodynamics research has mainly examined surface roughness, seams, permeability, and stretch as design variables, while heat-treatment condition a step in the fabric manufacturing process has received comparatively little attention as an independent variable for drag comparison.
Objectives
This study aimed to compare the drag coefficient (Cd) of sprintwear fabric under different heat-treatment conditions using wind-tunnel testing, and to examine whether the observed differences depend on model geometry and flow velocity. This preliminary study used a cylinder model and an airfoil-type model rather than aiming to provide definitive evidence of aerodynamic drag reduction.
Methods
Six fabric specimens were tested: 140°C single-side heat treatment, 140°C double-side heat treatment, 160°C single-side heat treatment, 180°C single-side heat treatment, untreated (control) fabric, and 200°C single-side heat treatment. Wind-tunnel tests were conducted at flow velocities of 7, 8, 9, 10, and 11 m/s. One physical specimen represented each heat-treatment condition, and three technical measurements of the same specimen were performed at each velocity; thus, the study did not include independently manufactured replicate specimens. The reference area was 0.030 m² for the cylinder model and 0.050 m² for the airfoil-type model, reflecting the fabric-covered area on both sides of the model. Results were compared primarily using mean Cd values, with standard deviations presented as error bars.
Results
In the airfoil-type model, several heat-treated specimens showed lower Cd than the untreated fabric (No.5). No.4 (180°C single-side) showed the largest reduction relative to No.5 at 9 m/s, approximately −20.4%. No.3 (160°C single-side) showed consistently lower Cd at 10 and 11 m/s, with reductions of approximately −15.1%. In the cylinder model, differences were much smaller, with most Cd changes relative to No.5 remaining within approximately ±3%. At 11 m/s in the cylinder model, the untreated fabric showed the lowest mean Cd; however, this result should be interpreted cautiously because the mean value may have been influenced by one comparatively low repeated measurement.
Conclusion
No single heat-treatment condition consistently produced the lowest Cd across all model geometries and flow velocities. Nevertheless, No.3 and No.4 may be considered candidate conditions for further investigation, particularly in the airfoil-type model. This study contributes by introducing heat-treatment temperature and treated-surface condition as manufacturing-process variables for the aerodynamic comparison of sprintwear fabrics.
Keywords: Skinsuit Aerodynamics; Fabric Surface Treatment; Airfoil Model; Cylinder Model; Reynolds Number; Sprint Performance