A numerical model is presented to simulate the fiber motion in the airflow inside the vortex spinning nozzle (VSN). The coupling between the fiber and airflow together with the fiber-wall contact is solved. Based on the numerical model, the motional characteristics of four types of fibers-cotton, viscose rayon, lyocell, and polyester fibers-in the airflow inside the vortex spinning nozzle are simulated and analyzed. The vortex yarn structure is viewed under the scanning electron microscope and the fiber strength utilization factors of the vortex yarns spun from different types of fibers are compared to verify the wrapping effects of different types of fibers in the vortex yarns obtained by the numerical simulation. The agreement between the numerical and experimental results shows that the numerical modeling methodology proposed in this research provides a reliable way of investigating the fiber dynamics in airflow and an efficient solution to the mechanical problems in polymer/textile manufacturing processes involving fluid-solid coupling. POLYM. ENG. SCI., 52:856-567, 2011. (C) 2011 Society of Plastics Engineers