Modeling the Fluid-Structure Interactions of a Hairy Yarn in Air-Jet Weaving: A Multiscale Approach

The interaction between air jets and hairy yarns is an important aspect in textile machinery. Currently, there is a need for high-fidelity two-way coupled Fluid-Structure Interaction (FSI) simulations of a hairy yarn subjected to high-speed air flows in textile processing, as these models are vital to understand yarn dynamics in, for example, air-jet weaving looms. Therefore, this work develops a fully three-dimensional two-way coupled FSI framework for modeling the yarn dynamics in air-jet weaving. The framework combines an adapted version of the Actuator Line Method (ALM) for the flow with beam elements for the structural representation of the yarn. This enables computationally efficient simulations at the machine scale without the need for resolving fiber-level details. Instead, these properties—derived in earlier work using microscale simulations—are homogenized into aerodynamic force coefficients and structural material parameters, resulting in a multiscale modeling approach. The framework is first validated on the launch of a nylon monofilament yarn, demonstrating its ability to predict yarn velocity and transversal oscillations while reducing the computational cost compared to existing overset mesh methods. In a second step, the method is applied to a hairy staple-fiber yarn, marking the first high-fidelity FSI simulation of such a system. The results confirm the potential of this approach for characterizing hairy yarn behavior in air-jet weaving without tuning of coefficients.