A model for the particle-level simulation of multiple flexible fibers moving in a wall-bounded fluid flow

Abstract

Airflow has wide and important applications in textile manufacturing. The dynamic behavior of fibers in the airflow can have a decisive influence on the structure and performance of the resultant textiles. In this paper, a three-dimensional model for the particle-level simulation of the dynamic behavior of multiple flexible fibers in a wall-bounded fluid flow of finite Reynolds number is proposed. The fiber is modeled as made up of a series of massless elastic rods connected by rigid ball-socket joints. In the model, both the internal and fluid forces and torques are applied on the ball-socket joints while the elastic rods only serve to transmit the internal forces and maintain the connectivity of the fiber without interacting with the ambient fluid. Each pair of adjacent elastic rods can bend and twist at the ball-socket joint connecting them, thus the stretching, bending and twisting deformations of the fiber can all be modeled. The motions of the fibers are governed by the translational and rotational equations for each ball-socket joint and both the fiber–fiber and fiber–wall interactions can be solved based on the hard sphere model. Using the proposed model, the regimes of the motion of a threadlike particle in a shear flow and the interaction of a single rigid fiber with a solid wall in Poiseuille flow are successfully reproduced, which agrees with the experimental results found in literature. The model is applied to the simulation of the motions of multiple flexible fibers in the airflow field inside the fiber transfer channel of the rotor spinning machine. Based on the simulation, the motional characteristics of the fibers as well as the effect of the transfer channel on the straightness and parallelization of the fibers are analyzed. The results indicate that the model proposed in this paper can provide an effective means of studying the dynamic behavior of the flexible fibers in the flow field involved in the textile production processes and a promising way of optimizing the design of the key components of textile machines.