An Efficient Numerical Framework for Fiber Spinning Scenarios with Evaporation Effects in Airflows

TL;DR

This paper introduces a reduced-dimensional numerical framework for simulating fiber spinning with evaporation effects, significantly improving computational efficiency while maintaining accuracy in modeling fiber-air interactions.

Contribution

A novel dimensionally reduced fiber model coupled with an efficient iterative algorithm for simulating evaporation and airflow effects in fiber spinning processes.

Findings

Accurate approximation of 3D fiber-air interactions with reduced computational cost.

Effective solution of integral equations using product integration method.

Numerical results closely match full 3D simulations, validating the approach.

Abstract

In many spinning processes, as for example in dry spinning, solvent evaporates out of the spun jets and leads to thinning and solidification of the produced fibers. Such production processes are significantly driven by the interaction of the fibers with the surrounding airflow. Faced with industrial applications producing up to several hundred fibers simultaneously, the direct numerical simulation of the three-dimensional multiphase, multiscale problem is computationally extremely demanding and thus in general not possible. In this paper, we hence propose a dimensionally reduced, efficiently evaluable fiber model that enables the realization of fiber-air interactions in a two-way coupling with airflow computations. For viscous dry spinning of an uni-axial two-phase flow, we deduce one-dimensional equations for fiber velocity and stress from cross-sectional averaging and combine them with two-dimensional advection-diffusion equations for polymer mass fraction and temperature revealing the radial effects that are observably present in experiments. For the numerical treatment of the resulting parametric boundary value problem composed of one-dimensional ordinary differential equations and two-dimensional partial differential equations we develop an iterative coupling algorithm. Thereby, the solution of the advection-diffusion equations is implicitly given in terms of Green's functions and leads for the surface values to Volterra integral equations of second kind with singular kernel, which we can solve very efficiently by the product integration method. For the ordinary differential equations a suitable collocation-continuation procedure is presented. Compared with the referential solution of a three-dimensional setting, the numerical results are very convincing. They provide a good approximation while drastically reducing the computational time.