Variation of the Recirculation Length of Newtonian and Non-Newtonian Power-Law Fluids in Laminar Flow Through a Suddenly Expanded Axisymmetric Geometry

2006 ◽  
Vol 129 (2) ◽  
pp. 245-250 ◽  
Author(s):  
Debabrata Nag ◽  
Amitava Datta
Keyword(s):  
Laminar Flow ◽  
Power Law ◽  
Numerical Study ◽  
Shear Thickening ◽  
Expansion Ratio ◽  
Rheological Parameters ◽  
Power Law Fluids ◽  
Wide Range ◽  
Flow Through ◽  
Recirculation Length

A numerical study has been carried out for the laminar flow of Newtonian and non-Newtonian power-law fluids through a suddenly expanded axisymmetric geometry. Mathematical correlations are proposed for the prediction of the length of the recirculating eddy in terms of Reynolds number, expansion ratio and rheological parameters. A wide range of expansion ratios (1.25⩽ER⩽8.0) has been covered for the Newtonian fluid and both the shear-thinning and shear-thickening flow characteristic fluids have been considered for the non-Newtonian fluids.

scholarly journals Collapse of a neutrally buoyant suspension column: from Newtonian to apparent non-Newtonian flow regimes

2017 ◽  
Vol 826 ◽  
pp. 918-941 ◽  
Author(s):  
A. Bougouin ◽  
L. Lacaze ◽  
T. Bonometti
Keyword(s):  
Power Law ◽  
Temporal Evolution ◽  
Volume Fraction ◽  
Fluid Model ◽  
Particle Diameter ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Rheological Parameters ◽  
Power Law Fluids ◽  
Neutrally Buoyant

Experiments on the collapse of non-colloidal and neutrally buoyant particles suspended in a Newtonian fluid column are presented, in which the initial volume fraction of the suspension $\unicode[STIX]{x1D719}$, the viscosity of the interstitial fluid $\unicode[STIX]{x1D707}_{f}$, the diameter of the particles $d$ and the mixing protocol, i.e. the initial preparation of the suspension, are varied. The temporal evolution of the slumping current highlights two main regimes: (i) an inertial-dominated regime followed by (ii) a viscous-dominated regime. The inertial regime is characterized by a constant-speed slumping which is shown to scale as in the case of a classical inertial dam-break. The viscous-dominated regime is observed as a decreasing-speed phase of the front evolution. Lubrication models for Newtonian and power-law fluids describe most of situations encountered in this regime, which strongly depends on the suspension parameters. The temporal evolution of the propagating front is used to extract the rheological parameters of the fluid models. At the early stages of the viscous-dominated regime, a constant effective shear viscosity, referred to as an apparent Newtonian viscous regime, is found to depend only on $\unicode[STIX]{x1D719}$ and $\unicode[STIX]{x1D707}_{f}$ for each mixing protocol. The obtained values are shown to be well fitted by the Krieger–Dougherty model whose parameters involved, say a critical volume fraction $\unicode[STIX]{x1D719}_{m}$ and the exponent of divergence, depend on the mixing protocol, i.e. the microscale interaction between particles. On a longer time scale which depends on $\unicode[STIX]{x1D719}$, the front evolution is shown to slightly deviate from the apparent Newtonian model. In this apparent non-Newtonian viscous regime, the power-law model, indicating both shear-thinning and shear-thickening behaviours, is shown to be more appropriate to describe the front evolution. The present experiments indicate that the mixing protocol plays a crucial role in the selection of a shear-thinning or shear-thickening type of collapse, while the particle diameter $d$ and volume fraction $\unicode[STIX]{x1D719}$ play a significant role in the shear-thickening case. In all cases, the normalized effective consistency of the power-law fluid model is found to be a unique function of $\unicode[STIX]{x1D719}$. Finally, an apparent viscoplastic regime, characterized by a finite length spreading reached at finite time, is observed at high $\unicode[STIX]{x1D719}$. This regime is mostly observed for volume fractions larger than $\unicode[STIX]{x1D719}_{m}$ and up to a volume fraction $\unicode[STIX]{x1D719}_{M}$ close to the random close packing fraction at which the initial column remains undeformed on opening the gate.

Experimental and Numerical Investigation of Gas-Yield Power-Law Fluids in a Horizontal Pipe

2019 ◽  
Author(s):  
Abdalsalam Ihmoudah ◽  
Mohamed M. Awad ◽  
Mohammad Azizur Rahman ◽  
Stephen D. Butt
Keyword(s):  
Power Law ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Superficial Velocity ◽  
Rheological Parameters ◽  
Phase Flow ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Power Law Fluids ◽  
Wide Range

Abstract Two-phase flow of gas/yield power-law (YPL) fluids in pipes can be found in a wide range of practical and industrial applications. To improve the understanding of the effects of rheological parameters of non-Newtonian liquids in a two-phase model, experimental and Computational Fluid Dynamics (CFD) investigations of gas/yield power-law fluids in a horizontal pipe were carried out. Two Xanthan gum (XG) solutions at concentrations of (0.05% and 0.10% by weight) were used as the working liquids. The experiments were conducted in a flow loop in a 65-m open-cycle system. The horizontal test section had a diameter of 3 inches (76.2 mm). The transient calculations were conducted using a Volume of Fluid (VOF) model in ANSYS Fluent version 17.2. Slug flow characteristics were recorded and observed by a high-speed digital camera in different operating conditions. The slug velocity and slug frequency were investigated experimentally and numerically, and a comparison of results with empirical relationships found in the literature was performed. We observed that the rheological properties of non-Newtonian phase influence the flow behavior in two-phase flow with increasing XG concentrations. The results of the empirical correlation to measure the slug frequency of a gas/non-Newtonian with considered the rheology of the shear-thinning behaver gave acceptable agreement with numerical measurements at low polymer concentration. The effect of liquid superficial velocity on slug translational velocity at low gas superficial velocity was relatively high.

Heat Transfer in Fully Developed Laminar Flow of Power Law Fluids

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
A. Baptista ◽  
M. A. Alves ◽  
P. M. Coelho
Keyword(s):  
Nusselt Number ◽  
Laminar Flow ◽  
Viscous Dissipation ◽  
Power Law ◽  
Numerical Solutions ◽  
Constant Heat Flux ◽  
Parallel Plates ◽  
Constant Wall Temperature ◽  
Power Law Fluids ◽  
Wide Range

In this work, we present approximate and exact solutions for the temperature profile and Nusselt number under fully developed laminar flow of a power law fluid inside pipes and between parallel plates. Constant wall temperature and negligible axial heat conduction are considered, for both the cases with and without viscous dissipation. For completeness, the corresponding solutions for the related problem of constant heat flux at the wall are also presented. In the absence of viscous dissipation, the solutions obtained are semi-analytic, since they rely upon an iterative procedure. As a benchmark result, to allow comparison with the results obtained with the semi-analytical expressions, we also present highly accurate numerical solutions for the Nusselt number, Nu, based on numerical integration of the energy equation. Also based on these numerical results, simplified correlations for Nu are proposed, valid for a wide range of the power law index.

A Numerical Study of Non-Isothermal Peristaltic Flow of Power-Law Fluids in a Circular Tube

2010 ◽  
Author(s):  
M. S. Yun ◽  
B. P. Huynh
Keyword(s):  
Reynolds Number ◽  
Power Law ◽  
Circular Tube ◽  
Numerical Study ◽  
Shear Thickening ◽  
Peristaltic Flow ◽  
Fluid Viscosity ◽  
Power Law Fluids ◽  
Fluid Behaviour ◽  
Power Law Index

Non-isothermal peristaltic flow of power-law fluids in a circular tube is investigated numerically, using a commercial Computational Fluid Dynamics (CFD) software package that employs the Finite Volume Method. Simulation is performed over the range of Reynolds-number values from 1 to 100. Temperature effect on the flow field is via fluid viscosity, which is assumed to decrease exponentially with temperature. Also, except for viscosity, other fluid properties are assumed to be constant, and are similar to those of an oil. Over a range of the power-law index covering fluid behaviour from shear-thinning, through Newtonian, to shear-thickening, it is found that allowing for temperature effects has significantly altered the flow pattern and pressure variation, even when the corresponding changes in temperature itself are small. Around the crest region, recirculation appears in non-isothermal flow at all power-law-index and Reynolds-number values considered in this work, in contrast to isothermal situations.

Bifurcation analysis of two-dimensional laminar flow through sudden expansion channel

2022 ◽  
Vol 13 (1) ◽  
pp. 0-0
Keyword(s):  
Laminar Flow ◽  
Expansion Ratio ◽  
Sudden Expansion ◽  
Two Dimensional ◽  
Governing Equations ◽  
Bifurcation Phenomena ◽  
Different Types ◽  
Fluent Software ◽  
Flow Through ◽  
Volume Method

In this work, bifurcation characteristics of unsteady, viscous, Newtonian laminar flow in two-dimensional sudden expansion and sudden contraction-expansion channels have been studied for different values of expansion ratio. The governing equations have been solved using finite volume method and FLUENT software has been employed to visualize the simulation results. Three different mesh studies have been performed to calculate critical Reynolds number (Recr) for different types of bifurcation phenomena. It is found that Recr decreases with the increase in expansion ratio (ER).

Laminar flow of power-law fluids past a rotating cylinder

2010 ◽  
Vol 165 (21-22) ◽  
pp. 1442-1461 ◽  
Author(s):  
Saroj K. Panda ◽  
R.P. Chhabra
Keyword(s):  
Laminar Flow ◽  
Power Law ◽  
Rotating Cylinder ◽  
Power Law Fluids
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