Numerical simulation of wicking in twisted yarn

To investigate the rapid capillary wicking behavior of twisted filament yarns over short vertical distances, this study employs a computational fluid dynamics simulation model to analyze and compare the liquid flow characteristics of yarns with varying structural configurations. To validate the model, a series of wicking experiments were conducted on polyester yarns using high-speed photography. The results demonstrate good agreement between the experimental data and the simulation outcomes. The study examines the effects of six twist levels, 0, 200, 400, 600, 800, and 1000 twists per meter (tpm), and four fiber packing arrangements, namely circumferential/open, hexagonal, and two variations of random packing, on the distribution of the liquid velocity field. The results reveal that with increasing twist, the wicking rate initially increases slightly or remains stable, but decreases significantly beyond 400 tpm. Among the structural configurations, circumferential packing more closely resembles the pore characteristics of random packing than hexagonal packing. While the predominant wicking direction follows axial migration, a minor lateral component of liquid flow is also observed.