Numerical Simulation of Fibre Suspension Flow through an Axisymmetric Contraction and Expansion Passages by Brownian Configuration Field Method

TL;DR

This paper combines finite element and Brownian Configuration Field methods to simulate fibre suspension flow in axisymmetric passages, revealing effects of fibre concentration and aspect ratio on vortex formation and improving numerical stability.

Contribution

It introduces a novel simulation approach using BFC and DAVSS methods for high concentration fibre suspensions in complex geometries, surpassing traditional models.

Findings

Vortex length predictions align well with experimental data.

Vortex size increases with fibre concentration in contraction flows.

BFC method better captures fibre motion effects than traditional aligned fibre approximation.

Abstract

In this paper, the finite element method is combined with the Brownian Configuration Field (BFC) method to simulate the fibre suspension flow in axisymmetric contraction and expansion passages. In order to solve for the high stress at high concentration, the Discrete Adaptive Viscoelastic Stress Splitting (DAVSS) method is employed. For the axisymmetric contraction and expansion passages with different geometry ratios, the results obtained are compared to available constitutive models and experiments. The predicted vortex length for dilute suspensions agrees well with experimental data in literature. Our numerical results show clearly the effect on vortex enhancement with increase of the volume fractions and the aspect ratios. Effect of aspect ratio of fibres on the vortex length is also studied. It is found that for the lower expansion ratio flows the vortex dimension in the corner region is fairly independent of fibre concentration and aspect ratio of fibres while the said vortex dimension increases with the increase of fibre concentration for contraction flows. The finding suggests that the aligned fibre approximation traditionally employed in previous work does not exactly describe the effect of fibre motion, and the present BFC method is deemed more suitable for the flow of dilute fibre suspensions. In terms of numerics, the employment of DAVSS enhances numerical stability in the presence of high concentration of fibre in the flow.