Accepted new paper in International Journal of Multiphase Flow

Characteristics of stratified flows of Newtonian/non-Newtonian shear-thinning fluids

Davide Picchi, Pietro Poesio, Amos Ullmann, Neima Brauner: Characteristics of stratified flows of Newtonian/non-Newtonian shear-thinning fluids. In: International Journal of Multiphase Flow, 97 , pp. 109-103, 2017.

Abstract

Exact solutions for laminar stratified flows of Newtonian/non-Newtonian shear-thinning fluids in horizontal and inclined channels are presented. An iterative algorithm is proposed to compute the laminar solution for the general case of a Carreau non-Newtonian fluid. The exact solution is used to study the effect of the rheology of the shear-thinning liquid on two-phase flow characteristics considering both gas/liquid and liquid/liquid systems. Concurrent and counter-current inclined systems are investigated, including the mapping of multiple solution boundaries. Aspects relevant to practical applications are discussed, such as the insitu hold-up, or lubrication effects achieved by adding a less viscous phase. A characteristic of this family of systems is that, even if the liquid has a complex rheology (Carreau fluid), the two-phase stratified flow can behave like the liquid is Newtonian for a wide range of operational conditions. The capability of the two-fluid model to yield satisfactory predictions in the presence of shear-thinning liquids is tested, and an algorithm is proposed to a priori predict if the Newtonian (zero shear rate viscosity) behaviour arises for a given operational conditions in order to avoid large errors in the predictions of flow characteristics when the power-law is considered for modelling the shear-thinning behaviour. Two-fluid model closures implied by the exact solution and the effect of a turbulent gas layer are also addressed.

BibTex

BibTeX (Download)

@article{Picchi_Poesio_Ullmann_Brauner_2017,
title = {Characteristics of stratified flows of Newtonian/non-Newtonian shear-thinning fluids},
author = {Davide Picchi and Pietro Poesio and Amos Ullmann and Neima Brauner},
doi = {10.1016/j.ijmultiphaseflow.2017.06.005},
year  = {2017},
date = {2017-12-01},
journal = {International Journal of Multiphase Flow},
volume = {97},
pages = {109-103},
abstract = {Exact solutions for laminar stratified flows of Newtonian/non-Newtonian shear-thinning fluids in horizontal and inclined channels are presented. An iterative algorithm is proposed to compute the laminar solution for the general case of a Carreau non-Newtonian fluid. The exact solution is used to study the effect of the rheology of the shear-thinning liquid on two-phase flow characteristics considering both gas/liquid and liquid/liquid systems. Concurrent and counter-current inclined systems are investigated, including the mapping of multiple solution boundaries. Aspects relevant to practical applications are discussed, such as the insitu hold-up, or lubrication effects achieved by adding a less viscous phase. A characteristic of this family of systems is that, even if the liquid has a complex rheology (Carreau fluid), the two-phase stratified flow can behave like the liquid is Newtonian for a wide range of operational conditions. The capability of the two-fluid model to yield satisfactory predictions in the presence of shear-thinning liquids is tested, and an algorithm is proposed to a priori predict if the Newtonian (zero shear rate viscosity) behaviour arises for a given operational conditions in order to avoid large errors in the predictions of flow characteristics when the power-law is considered for modelling the shear-thinning behaviour. Two-fluid model closures implied by the exact solution and the effect of a turbulent gas layer are also addressed.},
keywords = {Hold-up, Multiple Hold-up solutions, shape factor, Shear-thinning fluid, Stratified flow, Two-fluid model},
pubstate = {published},
tppubtype = {article}
}