Currently, the textile industry is energy-intensive as several processes require compressed air. In this sector, interaction between air jets and a yarn frequently occurs, but this interaction is not yet well understood. Unfortunately, current simulation techniques are too simplified to represent this interaction reliably. State-of-the-art techniques often simplify the flow field or use global coefficients to calculate the forces on the yarn and/or represent the yarn as a smooth cylinder instead of taking its fuzzy or hairy texture into account. Therefore, the goal of this research is to develop new simulation techniques that will enable the understanding of the interaction between air jets and a fuzzy yarn such that the energy consumption of the machines in the textile industry can be reduced. In the first work package, the focus will be on including the fuzzy texture of a yarn in computational fluid dynamics (CFD) simulations. To this extent, a multi-scale approach will be adopted where the boundary layer will be resolved on fiber scale in micro-scale simulations to extract local force coefficients. These coefficients then serve as input for a macro-scale actuator line model. The second work package focuses on the structural side where a beam element model for a yarn will be derived using multi-scale techniques as well. The third and final work package aims at combining these models into fluid-structure interaction (FSI) simulations of a complete yarn insertion.