Fluid Mechanics of Suspensions and Emulsions

A special issue of Fluids (ISSN 2311-5521). This special issue belongs to the section "Non-Newtonian and Complex Fluids".

Deadline for manuscript submissions: closed (20 January 2021) | Viewed by 13396

Special Issue Editor


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Guest Editor
Department of Chemical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Interests: rheology of complex fluids; composite nanomaterials; pickering emulsions; soft matter; thermodynamics
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Special Issue Information

Dear Colleagues,

This Special Issue of Fluids is dedicated to the fluid mechanics and rheology of suspensions and emulsions. Suspensions and emulsions are defined as two-phase dispersions consisting of fine insoluble inclusions distributed throughout a continuous liquid phase. The inclusion phase of the dispersion may be solid, liquid, or gas (Pal, R. Rheology of Particulate dispersions and Composites, CRC Press, Boca Raton, FL, USA, 2007). When the inclusion phase is solid particles, the dispersion is called suspension. When the inclusions are liquid droplets, the dispersions are referred to as emulsions. The special case of suspensions and emulsions is bubbly suspensions where the inclusions are gas bubbles.

Suspensions and emulsions are ubiquitous. They form a large group of materials of industrial importance. Some of the industries where suspensions and emulsions are relevant include food, household products, paints, cosmetics and toiletries, petroleum, biotechnology, and pharmaceuticals.

In this Special Issue of Fluids, experimental, theoretical, and simulation studies dealing with the rheology and fluid mechanics of suspensions and emulsions and related systems will be considered. Manuscripts dealing with the rheology and fluid mechanics of the following systems are welcome:

  • Suspensions of solid particles of different shapes and sizes including nano-suspensions;
  • Nano and macro emulsions including Pickering emulsions;
  • Suspensions of bubbles;
  • Suspensions of solid particles dispersed in non-Newtonian liquids;
  • Emulsions of droplets dispersed in non-Newtonian liquids.

Prof. Dr. Rajinder Pal
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Fluids is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • suspensions
  • emulsions
  • dispersions
  • nanofluids
  • nanoparticles
  • droplets
  • bubbles
  • rheology
  • non-Newtonian
  • two-phase flow

Published Papers (4 papers)

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Research

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21 pages, 6336 KiB  
Article
Effect of Water Content and Pectin on the Viscoelastic Improvement of Water-in-Canola Oil Emulsions
by Maria Romero-Peña and Supratim Ghosh
Fluids 2021, 6(6), 228; https://doi.org/10.3390/fluids6060228 - 18 Jun 2021
Cited by 4 | Viewed by 2596
Abstract
This study aimed to investigate gelation in glycerol monooleate (GMO)-stabilized water-in-canola oil (W/CO) emulsions by increasing water content (20–50 wt.%) and the addition of low methoxyl pectin (LMP) in the aqueous phase. A constant ratio of GMO to water was used to keep [...] Read more.
This study aimed to investigate gelation in glycerol monooleate (GMO)-stabilized water-in-canola oil (W/CO) emulsions by increasing water content (20–50 wt.%) and the addition of low methoxyl pectin (LMP) in the aqueous phase. A constant ratio of GMO to water was used to keep a similar droplet size in all emulsions. Hydrogenated soybean oil (7 wt.%) was used to provide network stabilization in the continuous phase. All fresh emulsions with LMP in the aqueous phase formed a stable and self-supported matrix with higher viscosity and gel strength than emulsions without LMP. Emulsion viscosity and gel strength increased with an increase in water content. All emulsions showed gel-like properties (storage moduli (G’) > loss moduli (G’’)) related to the presence of LMP in the aqueous phase and increased water content. Freeze/thaw analysis using a differential scanning calorimeter showed improved stability of the water droplets in the presence of LMP in the aqueous phase. This study demonstrated the presence of LMP in the aqueous phase, its interaction with GMO at the interface, and fat crystals in the continuous phase that could support the water droplets’ aggregation to obtain stable elastic W/CO emulsions that could be used as low-fat table spreads. Full article
(This article belongs to the Special Issue Fluid Mechanics of Suspensions and Emulsions)
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15 pages, 2614 KiB  
Article
CFD Analysis of Turbulent Fibre Suspension Flow
by Vijay Shankar, Anton Lundberg, Taraka Pamidi, Lars-Olof Landström and Örjan Johansson
Fluids 2020, 5(4), 175; https://doi.org/10.3390/fluids5040175 - 08 Oct 2020
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Abstract
A new model for turbulent fibre suspension flow is proposed by introducing a model for the fibre orientation distribution function (ODF). The coupling between suspended fibres and the fluid momentum is then introduced through the second and fourth order fibre orientation tensors, respectively. [...] Read more.
A new model for turbulent fibre suspension flow is proposed by introducing a model for the fibre orientation distribution function (ODF). The coupling between suspended fibres and the fluid momentum is then introduced through the second and fourth order fibre orientation tensors, respectively. From the modelled ODF, a method to construct explicit expressions for the components of the orientation tensors as functions of the flow field is derived. The implementation of the method provides a fibre model that includes the anisotropic detail of the stresses introduced due to presence of the fibres, while being significantly cheaper than solving the transport of the ODF and computing the orientation tensors from numerical integration in each iteration. The model was validated and trimmed using experimental data from flow over a backwards facing step. The model was then further validated with experimental data from a turbulent fibre suspension channel flow. Simulations were also carried out using a Bingham viscoplastic fluid model for comparison. The ODF model and the Bingham model performed reasonably well for the turbulent flow areas, and the latter model showed to be slightly better given the parameter settings tested in the present study. The ODF model may have good potential, but more rigorous study is needed to fully evaluate the model. Full article
(This article belongs to the Special Issue Fluid Mechanics of Suspensions and Emulsions)
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28 pages, 9476 KiB  
Article
New Generalized Viscosity Model for Non-Colloidal Suspensions and Emulsions
by Rajinder Pal
Fluids 2020, 5(3), 150; https://doi.org/10.3390/fluids5030150 - 01 Sep 2020
Cited by 21 | Viewed by 6297
Abstract
The viscous behavior of solids-in-liquid suspensions and liquid-in-liquid emulsions of non-Brownian solid particles and liquid droplets dispersed in Newtonian liquids is thoroughly discussed and reviewed. The full concentration range of the dispersed particles/droplets is covered, that is, 0<ϕ<ϕm [...] Read more.
The viscous behavior of solids-in-liquid suspensions and liquid-in-liquid emulsions of non-Brownian solid particles and liquid droplets dispersed in Newtonian liquids is thoroughly discussed and reviewed. The full concentration range of the dispersed particles/droplets is covered, that is, 0<ϕ<ϕm, where ϕ is the volume fraction of inclusions (particles or droplets) and ϕm is the maximum packing volume fraction of inclusions. The existing viscosity models for suspensions and emulsions are evaluated using a large pool of experimental viscosity data on suspensions and emulsions. A new generalized model for the viscosity of suspensions and emulsions is proposed and evaluated. The model takes into consideration the influence of shear-induced aggregation of particles and droplets. It also includes the effect of the droplet-to-matrix viscosity ratio λ on the viscosity of emulsions. In the limit of high ratio of droplet viscosity to matrix viscosity (λ), the model reduces to the suspension viscosity model. The proposed model uncovers some important and novel characteristics of suspension systems rarely discussed heretofore in the literature. The model is validated using twenty sets of experimental viscosity data on solids-in-liquid suspensions and twenty-three sets of experimental viscosity data on liquid-in-liquid emulsions. Full article
(This article belongs to the Special Issue Fluid Mechanics of Suspensions and Emulsions)
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Review

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13 pages, 6524 KiB  
Review
Electroviscous Effects in Stationary Solid Phase Suspensions
by Francisco J. Rubio-Hernández
Fluids 2021, 6(2), 69; https://doi.org/10.3390/fluids6020069 - 05 Feb 2021
Viewed by 2046
Abstract
Flowing through porous media is a matter of interest in different research fields such as medicine, engineering and science. The spontaneous appearance of ionic distribution at the solid liquid interface gives place to a reduction in the flow rate, which is generally named [...] Read more.
Flowing through porous media is a matter of interest in different research fields such as medicine, engineering and science. The spontaneous appearance of ionic distribution at the solid liquid interface gives place to a reduction in the flow rate, which is generally named electroviscous effect. However, this should be differentiated in two more specific effects, the primary effect due to the distortion of ionic clouds, and the secondary effect due to the overlapping of ionic clouds. Theoretical and experimental works have not always been clearly conducted in order to separate both effects. Instead, they have been globally grouped. The purpose of this review is to revise theoretical and experimental bibliography on the electroviscous effect in stationary solid phase suspensions (porous plugs, membranes, microchannels, capillaries). The main conclusions of this brief revision are: (i) when ionic clouds are relatively small, it is possible to accept that only the primary effect is the cause for the apparent increase of the viscosity of the liquid phase when it is forced to flow relative to the stationary solid phase; (ii) although theory predicts a maximum for the variation of the overall electroviscous effect vs the relative size of the ionic cloud, it has been experimentally observed but not properly reasoned that its existence depends on the salt type; and (iii) it is necessary to justify why, if the fluid is non-Newtonian, electrokinetic parameters dominate the characteristics of the flow due to high pressure gradients, but the rheological parameters are more decisive when the flow is generated by low pressure gradients. Full article
(This article belongs to the Special Issue Fluid Mechanics of Suspensions and Emulsions)
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