There are several processes where air jets interact with slender multi-component structures. One example can be found in textile machines. These processes typically span a large range of length scales. In air-jet weaving for example, these scales can range from the order of 20 µm on the fiber scale to 2 m on the machine scale, a factor of 100,000 difference. This makes it currently infeasible to account for fiber scale details in machine scale computer simulations. When considering yarn interactions with air jets, fiber scale behaviour should not be neglected however. The irregular fibrous surface structure of the yarn influences the air flow pattern around the multi-filament yarn and as such also the aerodynamic forces. From the structural point of view, the microstructure of the yarn determines the macroscopic behaviour. It is thus necessary to shift towards homogenized models on the macroscale level that account for the fibrous nature of the yarn on microscale level, for both the fluid and structural modelling. The current work proposes a methodology to represent a multi-component slender structure such as a yarn as an actuator line in an air jet. As such, several orders of magnitude can be gained on the smallest scales since the viscous boundary layer around the individual fibers no longer needs to be resolved. The aerodynamic forces acting on the yarn are calculated using the macroscale flow field and predetermined force coefficients. These force coefficients depend on the local flow velocity and orientation with respect to the yarn centerline and are calculated using microscale Computational Fluid Dynamics (CFD) simulations on a small portion of the yarn (length of ±2 mm). The geometry is obtained from microcomputed tomography (µCT) scan data on a wool fiber yarn. The meshing of this highly complex geometry is enabled by the overset technique, where each fiber is represented as a single cylindrical component mesh which is deformed according to the fiber’s centerline.