Numerical simulations using the closed form Adaptive Length Scale (ALS-C) model

Description

In this study the ALS-C model [1] is employed and we investigate its characteristics and potential use in numerical studies of dilute polymer solutions in general flows. The derivation of the ALS-C model was originally inspired by the ability of Kramers chain to capture important properties of dilute polymer solutions in rapidly varying extensional flows, such as coil-stretch hysteresis. The model is a generalised version of the Finitely Extensible Nonlinear Elastic model that follows the Peterlin approximation (FENE-P) and introduces a new variable which adapts to flow changes modifying the developed stresses. In proposing the model it was hoped that it would be capable of predicting the enhanced pressure drop observed in many flows of dilute polymeric solutions, but this hypothesis has never been tested in complex flows. To our knowledge, the ALS-C model has not been yet considered in flows outside of simple shear or extension and specifically not in any general computational fluid dynamics (CFD) simulations. Here, we present a robust approach to use the model for circumnavigating inherently problematic numerical issues. The model has been implemented into an in-house finite-volume CFD solver appropriate for viscoelastic fluid flows [2], which employs the log-conformation approach for enhanced stability [3]. Initially, the performance of the model is presented for standard rheological flows, followed by this of a fully-developed channel flow (non-homogeneous steady shear), illustrating its complexity. Finally, its potential to improve the flow characteristics in flows of complex geometries compared to the FENE-P model is shown, with particular emphasis placed on the estimation of the pressure-drop, demonstrating that it can create alternative routes for proposing new viscoelastic models.

[1] I Ghosh et al., J Rheol 46:1057 (2002)
[2] PJ Oliveira et al., J Non-Newton Fluid Mech, 79:1 (1998)
[3] A Afonso et al., J Non-Newton Fluid Mech 157:55 (2009)

Period	9 Jun 2021
Event title	XXth International Workshop on Numerical Methods for Non-Newtonian Flows (Online)
Event type	Workshop
Location	Oaxaca, MexicoShow on map
Degree of Recognition	International