Development and Validation of an Actuator Line Method for Fuzzy Yarns in High-Speed Air Flow

Abstract

Air-jet weaving relies on high-speed air flow to propel the weft yarns through the machine, achieving high insertion rates but at the cost of a significant energy demand. Capturing the interactions between the air jets and the weft yarns, which often have a fuzzy surface structure, is therefore vital in improving the air-jet weaving process. To achieve this, this work introduces a cost-efficient method to represent fuzzy staple-fibre yarns in Computational Fluid Dynamics (CFD) simulations by adapting the Actuator Line Method (ALM). The methodology addresses the drag-dominated aerodynamic forces acting on the yarn by introducing an upstream velocity sampling procedure. These forces are then introduced in the flow domain in a smooth and continuous manner using the actuator curve embedding principle, allowing relatively coarse mesh resolutions while still providing a correct prediction of the aerodynamic forces. The method is validated numerically through comparison with high-fidelity fibre-resolved simulations in uniform flow. Results show maximal errors in the force prediction of approximately $15\%$ in cross flow with narrow force regularization kernels and a force distribution error below $1\%$ while reducing the cell count by two orders of magnitude. Additionally, the methodology was also validated experimentally in non-uniform flow and the simulations of these jet flow experiments show excellent agreement with the measured aerodynamic forces on the yarns for various orientations and supply pressures. This actuator line approach significantly reduces the computational cost by bypassing the need for microscale flow resolution around fuzzy yarn surfaces. For this reason, it opens the door to large-scale coupled fluid-structure interaction (FSI) simulations of the yarn insertion process in air-jet weaving.