Investigation of the Dynamic Behavior of Flexible Fiber Free Ends During Vortex Spinning Process Based on an Enhanced Bead–Rod Model

Fibers in vortex turbulence fields involve complex gas–solid coupling effects, significantly influencing the spinning process within vortex nozzles. This paper utilizes the Discrete Element Method (DEM) to refine the existing rigid bead–elastic rod model describing fiber constitutive behavior. This improved model is used to numerically simulate the dynamic behavior of a single flexible fiber within the vortex field of the nozzle. Based on elastic mechanics, this study establishes mapping functions converting relative displacement and angular displacement between beads into internal forces and torques within the beads. A contact model is also developed to handle fiber–wall interactions. The effects of different nozzle structures on fiber motion are investigated. The improved model successfully simulates the entire motion process of a single fiber during spinning. Its reliability is validated by comparing with experimentally collected fiber motion data. The study reveals that a twist chamber diameter of 6 mm, a conical cavity angle of 55 degrees, and a distance of 1.05 mm between the jet orifice and the hollow spindle yield optimal fiber twist count and wrapping density. This research provides effective insights for developing textile equipment that relies on airflow to drive fiber spinning and contributes to establishing a comprehensive twisting mechanism.