Applied Rheology: Publications

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F.J. Rubio-Hernandez, A.I. Gomez-Merino, J.F. Velazquez-Navarro, L. Parras
4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013)

Appl. Rheol. 23:6 (2013) 374-375

Cite this publication as follows:
Rubio-Hernandez F, Gomez-Merino A, Velazquez-Navarro J, Parras L: 4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013), Appl. Rheol. 23 (2013) 374.

Justyna Czerwinska
12th Swiss Soft Days (SSD 12)

Appl. Rheol. 23:6 (2013) 375-376

Cite this publication as follows:
Czerwinska J: 12th Swiss Soft Days (SSD 12), Appl. Rheol. 23 (2013) 375.

Peter Fischer
Understanding Viscoelasticity - An Introduction to Rheology (Nhan Phan-Thien)

Appl. Rheol. 23:6 (2013) 329-329

Cite this publication as follows:
Fischer P: Understanding Viscoelasticity - An Introduction to Rheology (Nhan Phan-Thien), Appl. Rheol. 23 (2013) 329.

S.O.S. Echendu, H.R. Tamaddon-Jahromi, M.F. Webster
Modelling Reverse Roll Coating flow with dynamic wetting lines and inelastic shear thinning fluids

Appl. Rheol. 23:6 (2013) 62388 (13 pages)

This study addresses the Taylor-Galerkin/pressure-correction solution of industrial high-speed reverse roller coating flow associated with thin-film paint-coatings of strip-steel. Novel aspects lie in the inclusion of the dynamic wetting line and flow analysis due to surface tension and inelastic rheology effects, via shear-thinning and lowering high shear viscosity levels. The main aim of the study is to predict the zonal flow influences by examining viscous flow structures around the meniscus, nip and wetting line regions, conveyed via streamline and shear rate patterns, surface distributional lift and localised nip-pressures. The majority of this study focuses on the secondary nip-vortex and its influences on the contact point and dynamic wetting line. This aspect of the flow provides the driving mechanism for the onset of instabilities, which governs the entire process and tends to determine the consistency of the film thickness at the outflow. Positive peak-pressures tend to increase with decrease in nip-gap size. At low nip-gap size, negative peak pressures are observed around the substrate-wetting line contact region. At higher speed-ratios, positive peak pressures are seen to increase with less recirculation apparent around the contact zone. Significantly and upon surface tension increase, the dynamic wetting line is sucked further inwards towards the nip-gap, stimulating a localised wetting line-foil third vortex structure, which causes an apparent reduction in film-leakage thickness.

Cite this publication as follows:
Echendu S, Tamaddon-Jahromi H, Webster M: Modelling Reverse Roll Coating flow with dynamic wetting lines and inelastic shear thinning fluids, Appl. Rheol. 23 (2013) 62388.

Edson Jose Soares, Roney Leon Thompson, Andre Machado
Measuring the yielding of waxy crude oils considering its time-dependency and apparent-yield-stress nature

Appl. Rheol. 23:6 (2013) 62798 (11 pages)

Production in reservoirs located in deep and ultra-deep water that contain waxy crude oils faces a huge obstacle imposed by the low temperatures of the environment. When the waxy crude oil is subjected to a temperature below the Gelation Temperature, as in the case investigated in the present work, it exhibits a variety of non-Newtonian features: elasticity, plasticity, viscous effects, and time-dependency, which renders to this material a highly complex behavior. A crucial feature that is frequently ignored when the determination of the yield stress is being carried out, is the time-dependency nature of these materials. We demonstrate how significantly different values of yield stress can be obtained if this character of the material is neglected. We use the asphaltenes properties as inhibitors of wax formation and propose a protocol to capture yield-stress parameters. One important conclusion is that waxy crude oils can be classified as apparent-yield-stress fluids, and not (true-) yield-stress materials, with the presence of a dynamic and a static yield-stresses.

Cite this publication as follows:
Soares EJ, Thompson RL, Machado A: Measuring the yielding of waxy crude oils considering its time-dependency and apparent-yield-stress nature, Appl. Rheol. 23 (2013) 62798.

Nsenda Ngenda Tshilumbu, Irina Masalova
Effect of nanoparticle hydrophobicity on the rheology of highly concentrated emulsions

Appl. Rheol. 23:6 (2013) 62835 (11 pages)

A series of fumed silica nanoparticles were used as an additional emulsifier for highly concentrated (HC) water-in-oil (W/O) emulsions. These nanoparticles, with different hydrophobicity index (HI) in the 0.60 - 1.34 and HI > 3 range, were mixed with the conventional low molecular weight surfactant, sorbitan monooleate (SMO), in the oil phase prior to the emulsification process. The rheological properties of these emulsions were measured and compared with the properties of emulsions stabilized with SMO alone. In the mixed emulsifier system, the changes in rheological parameters were clearly expressed as a function of HI. The mixture of silica nanoparticles and SMO significantly increases the yield stress and plateau modulus of fresh emulsion, compared to the SMO only system. The effect was found to be more pronounced with a decrease in the HI. This is probably related to the reduction in micelle content with the decrease in HI, owing to a concomitant increase in the amount of SMO adsorbed onto the particle surface. Then, interestingly, the Foudazi-Masalova model recently developed for surfactant-stabilized highly concentrated emulsions (HCE) was found to describe successfully the rheological behavior of emulsions in the presence of a mixture of surfactant and fumed nanosilica.

Cite this publication as follows:
Tshilumbu NN, Masalova I: Effect of nanoparticle hydrophobicity on the rheology of highly concentrated emulsions, Appl. Rheol. 23 (2013) 62835.

Alexandre Pierre, Christophe Lanos, Patrice Estelle
Extension of spread-slump formulae for yield stress evaluation

Appl. Rheol. 23:6 (2013) 63849 (9 pages)

This paper provides a new model to evaluate the yield stress of suspensions, slurries or pastes, based on the release of a finite volume of material onto a horizontal surface. Considering the height (h) and the radius (R) of the sample at the flow stoppage, two asymptotic regimes, where h > R or h < R, lead to different analytical models that allow the determination of yield stress. Experimental observations show typical sample shape at stoppage between slump (h > R) and spread (h < R). Based on these observations, we have developed a new analytical model to evaluate accurately the yield stress of materials in this intermediate regime. The validity of this model was evaluated from data obtained using various Carbopol(c) dispersions. The yield stress measured with the proposed model was compared with the yield stress evaluated from shear flow curves obtained with roughened plate/plate geometry fitted to the Herschel-Bulkley model. Results show the relevance of the proposed model which that can be applied in the range between models used for the two asymptotic regimes.

Cite this publication as follows:
Pierre A, Lanos C, Estelle: Extension of spread-slump formulae for yield stress evaluation, Appl. Rheol. 23 (2013) 63849.


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