Computational fluid dynamics modeling in yarn engineering

Abstract

This chapter deals with the application of computational fluid dynamics (CFD) modeling in reducing yarn hairiness during the ring spinning process and thereby “engineering” yarn with desired properties. Hairiness significantly affects the appearance of yarns and fabrics. The presence of a large number of hairs on yarn surfaces gives a fuzzy appearance to the resultant fabric and a greater tendency for pill formation in the fabric. As increasingly strict requirements are placed on yarns in high performance oriented weaving and knitting, the hairiness of yarns needs to be reduced to avoid entanglement of yarns and end breakages in subsequent processing. This has resulted in the development of new nozzle profiles to address the problem. The airflow pattern in the nozzles plays a significant role in the reduction of hairiness. CFD has been effectively utilized in yarn engineering to understand the actual mechanism of reducing yarn hairiness. The influence of different nozzle parameters such as diameter and axial angle of the nozzle in reducing yarn hairiness are investigated with the help of CFD. Other factors such as air pressure in the nozzles in affecting the tendency of reducing hairiness in different types of yarn are also investigated. The influence of drag force and impact angle of airflow on reducing yarn hairiness is also discussed. The yarns spun with the nozzles show a significant reduction in hairiness (36-60%) in comparison to the normal yarns spun without using nozzles. CFD modeling of airflow inside the nozzles provides a new direction in addressing the problem of hairiness characteristics in yarn engineering.