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Rheology of Advanced Complex Fluids

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Nanomaterials and Nanotechnology".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 33476

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Dr. Yannis Dimakopoulos

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Laboratory of Fluid Mechanics and Rheology, Department of Chemical Engineering, University of Patras, 26504 Patras, Greece
Interests: transport phenomena; non-newtonian fluid mechanics; rheology of complex fluids; hemorheology; biomechanics; large scales simulations; rheological modeling

Special Issue Information

Dear Colleagues,

The deformation and flow of polymeric or structured materials, which are also called complex fluids, is essentially controlled by their molecular chemistry and, consequently, their inherent rheological properties, their so-called material functions. Synthetic or biological structured fluids contain more than one phase, such as solid particles dispersed in a liquid, gas particles in foam, or an emulsion of immiscible liquids. On the other hand, polymeric and biopolymeric fluids have macromolecular structures. In the first case, the rheological behavior is dominated by the interactions of the constituents, while in the second one, intramolecular forces and chain entanglements play a crucial role. The continuous effort to predict and control the rheological response of complex fluids has led to a prolonged collaboration between industry, research institutes, and academia. The current Issue aims to host contributions related to measurements through experimental methods, characterization through advanced rheometric protocols, and the constitutive modeling and flow simulation of such fluids.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. Yannis Dimakopoulos
Guest Editor

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Keywords

polymer and biopolymer rheology
synthetic and biological structured fluids
constitutive modeling
experimental rheology
meso- and macro-scopic flow simulations
transport phenomena of complex fluids

Published Papers (11 papers)

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Research

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15 pages, 1162 KiB

Open AccessArticle

Fractal Analysis of a Non-Newtonian Fluid Flow in a Rough-Walled Pipe

by Abdellah Bouchendouka, Zine El Abiddine Fellah, Zakaria Larbi, Zineeddine Louna, Erick Ogam, Mohamed Fellah and Claude Depollier

Materials 2022, 15(10), 3700; https://doi.org/10.3390/ma15103700 - 22 May 2022

Cited by 4 | Viewed by 1824

Abstract

The fully developed laminar flow of a viscous non-Newtonian fluid in a rough-walled pipe is considered. The fluid rheology is described by the power–law model (covering shear thinning, Newtonian, and shear thickening fluids). The rough surface of the pipe is considered to be fractal, and the surface roughness is measured using surface fractal dimensions. The main focus of this study lies in the theoretical investigation of the influence of the pipe surface roughness on the velocity profile and the Darcy friction factor of an incompressible non-Newtonian fluid. The plotted results demonstrate that shear thinning fluids are the most sensitive to the surface roughness compared with Newtonian and shear thickening fluids. For a particular value of the surface fractal dimension, there exists an intersection point where shear thinning, Newtonian, and shear thickening fluids behave the same way regarding the amplitude of the velocity profile and the friction factor. This approach has a variety of potential applications, for instance fluid dynamics in hydrology, blood flow in the cardiovascular system, and many industrial applications. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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13 pages, 4372 KiB

Open AccessArticle

Lubricity and Rheological Properties of Highly Dispersed Graphite in Clay-Water-Based Drilling Fluids

by Quande Wang, Michal Slaný, Xuefan Gu, Zhipeng Miao, Weichao Du, Jie Zhang and Chen Gang

Materials 2022, 15(3), 1083; https://doi.org/10.3390/ma15031083 - 30 Jan 2022

Cited by 17 | Viewed by 2784

Abstract

Improving the tribological characteristics of water-based drilling fluids by adding graphene-based lubricants has garnered attention because of the potential for a range of inorganic-material-based additives at high temperature. In this study, we constructed a green and simple adsorption approach to prepare highly dispersed graphite using a cationic surfactant for graphite modification. The findings demonstrated that the prepared graphite was highly dispersed in water and had a low sedimentation rate and small contact angle in distilled water. The concentration dosage of cetyltrimethylammonium chloride (CTAC) on graphite was 0.02 g/g. We evaluated the performance of the modified graphite as a lubricated additive in water-based drilling through a rheological study and viscosity coefficient measurement. The results showed that the viscosity coefficient of drilling fluid with 0.05% modified graphite was reduced by 67% at 180 °C. We proved that the modified graphite can significantly improve the lubrication performance of drilling fluid. Furthermore, we revealed the lubrication mechanism by analyzing the chemical structural and crystalline and morphological features of graphite through a particle size test, zeta potential test, Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) measurements. The results indicated that the modification of graphite by CTAC only occurs through physical adsorption, without changing the crystal structure. These findings provide a reference for the development of high-performance water-based drilling fluids. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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15 pages, 2264 KiB

Open AccessArticle

Rheological Properties of Industrial Hot Trub

by Marta Stachnik, Monika Sterczyńska, Emilia Smarzewska, Anna Ptaszek, Joanna Piepiórka-Stepuk, Oleg Ageev and Marek Jakubowski

Materials 2021, 14(23), 7162; https://doi.org/10.3390/ma14237162 - 24 Nov 2021

Cited by 3 | Viewed by 2024

Abstract

The boiling of beer wort with hops results in the formation of a hot trub, a sediment consisting mainly of water-insoluble tannin and protein conglomerates and hop residue. Hot trub is a waste product, removed in a clarifying tank and discarded. The use of barley malt substitutes in recipes for beer is associated with an increase in the amount of generated hot trub. In presented study, an analysis of the rheological properties of industrial hot trub was carried out. Samples varied with regard to the quantities of unmalted barley (0%, 35%, and 45%) and worts’ extract (12.5, 14.1, 16.1, and 18.2 °Plato) in the recipe. The rheology of each type of sludge was determined using a hysteresis loop at four different temperatures. The results showed the shear-thinning and thixotropic properties of the hot trub. It was found that, regardless of the raw material and extract used, all samples exhibited the same rheological properties, but with different values. It was also proved that both raw material composition and temperature affected the hot trub’s rheology. The highest values of viscosity were identified for malted barley, whereas the lowest apparent viscosity values were recorded for the hot trub with a 30% addition of unmalted barley. The Herschel–Bulkley model had the best fit to the experimental data. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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29 pages, 1388 KiB

Open AccessArticle

Viscosity Model for Nanoparticulate Suspensions Based on Surface Interactions

by Benedikt Finke, Clara Sangrós Giménez, Arno Kwade and Carsten Schilde

Materials 2021, 14(11), 2752; https://doi.org/10.3390/ma14112752 - 23 May 2021

Cited by 3 | Viewed by 1836

Abstract

In this paper, a widely mechanistic model was developed to depict the rheological behaviour of nanoparticulate suspensions with solids contents up to 20 wt.%, based on the increase in shear stress caused by surface interaction forces among particles. The rheological behaviour is connected to drag forces arising from an altered particle movement with respect to the surrounding fluid. In order to represent this relationship and to model the viscosity, a hybrid modelling approach was followed, in which mechanistic relationships were paired with heuristic expressions. A genetic algorithm was utilized during model development, by enabling the algorithm to choose among several hard-to-assess model options. By the combination of the newly developed model with existing models for the various physical phenomena affecting viscosity, it can be applied to model the viscosity over a broad range of solids contents, shear rates, temperatures and particle sizes. Due to its mechanistic nature, the model even allows an extrapolation beyond the limits of the data points used for calibration, allowing a prediction of the viscosity in this area. Only two parameters are required for this purpose. Experimental data of an epoxy resin filled with boehmite nanoparticles were used for calibration and comparison with modelled values. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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26 pages, 4262 KiB

Open AccessEditor’s ChoiceArticle

Effect of D-Mannitol on the Microstructure and Rheology of Non-Aqueous Carbopol Microgels

by Simona Migliozzi, Panagiota Angeli and Luca Mazzei

Materials 2021, 14(7), 1782; https://doi.org/10.3390/ma14071782 - 04 Apr 2021

Cited by 1 | Viewed by 2413

Abstract

D-mannitol is a common polyol that is used as additive in pharmaceutical and personal care product formulations. We investigated its effect on the microstructure and rheology of novel non-aqueous Carbopol dispersions employing traditional and time-resolved rheological analysis. We considered two types of sample, (i) fresh (i.e., mannitol completely dissolved in solution) and aged (i.e., visible in crystalline form). The analysis of the intracycle rheological transitions that were observed for different samples revealed that, when completely dissolved in solution, mannitol does not alter the rheological behaviour of the Carbopol dispersions. This highlights that the chemical similarity of the additive with the molecules of the surrounding solvent allows preserving the swollen dimension and interparticle interactions of the Carbopol molecules. Conversely, when crystals are present, a hierarchical structure forms, consisting of a small dispersed phase (Carbopol) agglomerated around a big dispersed phase (crystals). In keeping with this microstructural picture, as the concentration of Carbopol reduces, the local dynamics of the crystals gradually start to control the integrity of the microstructure. Rheologically, this results in a higher elasticity of the suspensions at infinitesimal deformations, but a fragile yielding process at intermediate strains. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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36 pages, 9269 KiB

Open AccessEditor’s ChoiceArticle

Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

by Konstantinos Giannokostas, Yannis Dimakopoulos, Andreas Anayiotos and John Tsamopoulos

Materials 2021, 14(2), 367; https://doi.org/10.3390/ma14020367 - 13 Jan 2021

Cited by 15 | Viewed by 2588

Abstract

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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17 pages, 2610 KiB

Open AccessArticle

Effect of Particle Specific Surface Area on the Rheology of Non-Brownian Silica Suspensions

by Anastasia Papadopoulou, Jurriaan J. J. Gillissen, Manish K. Tiwari and Stavroula Balabani

Materials 2020, 13(20), 4628; https://doi.org/10.3390/ma13204628 - 16 Oct 2020

Cited by 10 | Viewed by 2189

Abstract

Industrial formulations very often involve particles with a broad range of surface characteristics and size distributions. Particle surface asperities (roughness) and porosity increase particle specific surface area and significantly alter suspension rheology, which can be detrimental to the quality of the end product. We examine the rheological properties of two types of non-Brownian, commercial precipitated silicas, with varying specific surface area, namely PS52 and PS226, suspended in a non-aqueous solvent, glycerol, and compare them against those of glass sphere suspensions (GS2) with a similar size distribution. A non-monotonic effect of the specific surface area (

S

) on suspension rheology is observed, whereby PS52 particles in glycerol are found to exhibit strong shear thinning response, whereas such response is suppressed for glass sphere and PS226 particle suspensions. This behaviour is attributed to the competing mechanisms of particle–particle and particle–solvent interactions. In particular, increasing the specific surface area beyond a certain value results in the repulsive interparticle hydration forces (solvation forces) induced by glycerol overcoming particle frictional contacts and suppressing shear thinning; this is evidenced by the response of the highest specific surface area particles PS226. The study demonstrates the potential of using particle specific surface area as a means to tune the rheology of non-Brownian silica particle suspensions. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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43 pages, 9695 KiB

Open AccessArticle

Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Description of the Model and Rheological Predictions

by Konstantinos Giannokostas, Pantelis Moschopoulos, Stylianos Varchanis, Yannis Dimakopoulos and John Tsamopoulos

Materials 2020, 13(18), 4184; https://doi.org/10.3390/ma13184184 - 20 Sep 2020

Cited by 32 | Viewed by 6137

Abstract

This work focuses on the advanced modeling of the thixotropic nature of blood, coupled with an elasto-visco-plastic formulation by invoking a consistent and validated model for TEVP materials. The proposed model has been verified for the adequate description of the rheological behavior of suspensions, introducing a scalar variable that describes dynamically the level of internal microstructure of rouleaux at any instance, capturing accurately the aggregation and disaggregation mechanisms of the RBCs. Also, a non-linear fitting is adopted for the definition of the model’s parameters on limited available experimental data of steady and transient rheometric flows of blood samples. We present the predictability of the new model in various steady and transient rheometric flows, including startup shear, rectangular shear steps, shear cessation, triangular shear steps and LAOS tests. Our model provides predictions for the elasto-thixotropic mechanism in startup shear flows, demonstrating a non-monotonic relationship of the thixotropic index on the shear-rate. The intermittent shear step test reveals the dynamics of the structural reconstruction, which in turn is associated with the aggregation process. Moreover, our model offers robust predictions for less examined tests such as uniaxial elongation, in which normal stress was found to have considerable contribution. Apart from the integrated modeling of blood rheological complexity, our implementation is adequate for multi-dimensional simulations due to its tensorial formalism accomplished with a single time scale for the thixotropic effects, resulting in a low computational cost compared to other TEVP models. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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18 pages, 6709 KiB

Open AccessArticle

Simple, Accurate and User-Friendly Differential Constitutive Model for the Rheology of Entangled Polymer Melts and Solutions from Nonequilibrium Thermodynamics

by Pavlos S. Stephanou, Ioanna Ch. Tsimouri and Vlasis G. Mavrantzas

Materials 2020, 13(12), 2867; https://doi.org/10.3390/ma13122867 - 26 Jun 2020

Cited by 11 | Viewed by 2461

Abstract

In a recent reformulation of the Marrucci-Ianniruberto constitutive equation for the rheology of entangled polymer melts in the context of nonequilibrium thermodynamics, rather large values of the convective constraint release parameter β_ccr had to be used in order for the model not to violate the second law of thermodynamics. In this work, we present an appropriate modification of the model, which avoids the splitting of the evolution equation for the conformation tensor into an orientation and a stretching part. Then, thermodynamic admissibility simply dictates that β_ccr ≥ 0, thus allowing for more realistic values of β_ccr to be chosen. Moreover, and in view of recent experimental evidence for a transient stress undershoot (following the overshoot) at high shear rates, whose origin may be traced back to molecular tumbling, we have incorporated additional terms into the model accounting, at least in an approximate way, for non-affine deformation through a slip parameter ξ. Use of the new model to describe available experimental data for the transient and steady-state shear and elongational rheology of entangled polystyrene melts and concentrated solutions shows close agreement. Overall, the modified model proposed here combines simplicity with accuracy, which renders it an excellent choice for managing complex viscoelastic fluid flows in large-scale numerical calculations. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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28 pages, 4807 KiB

Open AccessArticle

Viscoplastic Couette Flow in the Presence of Wall Slip with Non-Zero Slip Yield Stress

by Yiolanda Damianou, Pandelitsa Panaseti and Georgios C. Georgiou

Materials 2019, 12(21), 3574; https://doi.org/10.3390/ma12213574 - 31 Oct 2019

Cited by 10 | Viewed by 3249

Abstract

The steady-state Couette flow of a yield-stress material obeying the Bingham-plastic constitutive equation is analyzed assuming that slip occurs when the wall shear stress exceeds a threshold value, the slip (or sliding) yield stress. The case of Navier slip (zero slip yield stress) is studied first in order to facilitate the analysis and the discussion of the results. The different flow regimes that arise depending on the relative values of the yield stress and the slip yield stress are identified and the various critical angular velocities defining those regimes are determined. Analytical solutions for all the regimes are presented and the implications for this important rheometric flow are discussed. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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Review

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12 pages, 3664 KiB

Open AccessReview

Research Progress on the Collaborative Drag Reduction Effect of Polymers and Surfactants

by Yunqing Gu, Songwei Yu, Jiegang Mou, Denghao Wu and Shuihua Zheng

Materials 2020, 13(2), 444; https://doi.org/10.3390/ma13020444 - 17 Jan 2020

Cited by 90 | Viewed by 4813

Abstract

Polymer additives and surfactants as drag reduction agents have been widely used in the field of fluid drag reduction. Polymer additives can reduce drag effectively with only a small amount, but they degrade easily. Surfactants have an anti-degradation ability. This paper categorizes the mechanism of drag reducing agents and the influencing factors of drag reduction characteristics. The factors affecting the degradation of polymer additives and the anti-degradation properties of surfactants are discussed. A mixture of polymer additive and surfactant has the characteristics of high shear resistance, a lower critical micelle concentration (CMC), and a good drag reduction effect at higher Reynolds numbers. Therefore, this paper focuses more on a drag reducing agent mixed with a polymer and a surfactant, including the mechanism model, drag reduction characteristics, and anti-degradation ability. Full article

(This article belongs to the Special Issue Rheology of Advanced Complex Fluids)

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