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Papers by Sylwia Różańska

Inżynieria i Aparatura Chemiczna, 2007

We consider the inhomogeneous extensional response of a new constitutive model, the VCM model [Va... more We consider the inhomogeneous extensional response of a new constitutive model, the VCM model [Vasquez, et al., 2007. A network scission model for wormlike micellar solutions I: model formulation and homogeneous flow predictions. J. Non-Newt. Fluid Mech. 144, 122-139] that has been developed to describe concentrated solutions of wormlike micelles. The time dependent numerical analysis is carried out in a simplified slender filament formulation appropriate for transient elongational flows of complex fluids. The simulations show that, beyond a critical extension rate, elongating filaments of a micellar fluid described by the VCM model exhibit a dramatic and sudden rupture event as a result of the scission of the entangled wormlike chains. The computations capture many of the features of the high-speed rupture process observed experimentally [Bhardwaj, et al., 2007. Filament stretching and capillary breakup extensional rheometry measurements of viscoelastic wormlike micelle solutions. J. Rheol. 51, 693-719] in filament stretching experiments with wormlike micelle solutions. The highly localized rupture predicted by the VCM model and the corresponding evolution in the tensile force within the filament is contrasted with the familiar and more gradual necking responses predicted by the upper convected Maxwell and Giesekus models under equivalent kinematic boundary conditions.

Polimery, Oct 1, 2015

Porównano w³aoeciwooeci reologiczne, w przep³ywie rozci¹gaj¹cym i oecinaj¹cym, wodnych roztworów ... more Porównano w³aoeciwooeci reologiczne, w przep³ywie rozci¹gaj¹cym i oecinaj¹cym, wodnych roztworów polimerów: jonowego poliakryloamidu (WF2) oraz niejonowych-czêoeciowo zhydrolizowanego poliakryloamidu (WF1) i hydroksyetylocelulozy (HEC)-ró¿ni¹cych siê budow¹ ³añcucha polimerowego. Pomiary w przep³ywie rozci¹gaj¹cym wykonano z wykorzystaniem reometru w³asnej konstrukcji. Uzyskane wyniki wskazuj¹, ¿e polimery o giêtkiej budowie ³añcucha polimerowego (WF1, WF2) charakteryzuj¹ siê wiêkszymi wartooeciami pozornej lepkooeci wzd³u¿nej i stosunku Troutona (Tr B). W przypadku polimerów o sztywnej budowie ³añcucha (HEC), w zakresie pozornej szybkooeci rozci¹gania od 1 do 8 s-1 , liczba Tr B przybiera w przybli¿eniu wartooeae sta³¹ z przedzia³u 3-5. W przypadku wiêkszych wartooeci szybkooeci rozci¹gania (& e a) liczba Tr B zwiêksza siê do ok. 41.

Polish Journal of Chemical Technology

The paper presents the results of experimental studies on pressure drops during the flow of cocam... more The paper presents the results of experimental studies on pressure drops during the flow of cocamidopropyl betaine (CAPB) and DEA cocamide solutions with the addition of ethylene glycol. The degree of drag reduction during the flow of the CAPB/DEA aqueous solution and with the 10% addition of ethylene glycol was similar. A significant reduction in pressure drops was also observed at the 20% concentration of ethylene glycol. However, the increase in the concentration of ethylene glycol resulted in the reduction of flow resistance at higher temperatures. The resistance of the micellar microstructure of CAPB/DEA solutions to mechanical degradation depends strongly on the pH level. Significant changes in flow properties were observed when the initial pH was alkaline. The solution with initial pH close to neutral was stable over time, though reduced resistance to degradation with time was also observed.

Food is a very complex structured material, which is made up of water, proteins, carbohydrates, f... more Food is a very complex structured material, which is made up of water, proteins, carbohydrates, fats, and significant amount of fibers. All these constituents influence flow and structural behavior of foods significantly, and therefore, rheological properties of food are very dissimilar from the conventional polymeric materials. There are various factors that affect the stability of structured fluids. The viscosity of the liquid phase in dispersions mostly plays a major role in the flow properties of the material. Food rheology is no longer a measurement of apparent viscosity only. With time and advancement in instrumentation, food rheology today provides more in-depth information on microstructure and fluidity of a food. A transformation of measurement from a rotational viscometry to either controlled stress/strain rheometer or more advanced optimal Fourier transformation rheometry brought the accuracy, sophistication, and reliability on rheological data. There is a growing interest to understand the food microstructure and its correlation with the food textural and rheological attributes in food product development in academia and food industry. This knowledge on food rheology and microstructure helps in minimizing textural defects in the processed foods and improving consumer satisfaction. Our book "Advances in Food Rheology and Applications" is thematically divided into two broad areas: theoretical concepts and applications in the areas of food rheology. Chapters 1-10 contribute mainly in the selected theoretical aspects of food rheology, whereas Chapters 11-21 focus on practical applications of rheological concepts in gums, gels, emulsion, and selected commercial food products. Fluid and semisolid food products (eg, mayonnaise, peanut butter, chocolate, ketch up) are regularly monitored by rheological testing for the quality maintenance. Both steady and oscillatory rheological tests are used to

Materials, Jan 2, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Lecture Notes on Multidisciplinary Industrial Engineering, 2018

The flow through porous media plays an important role within several areas of science. In many re... more The flow through porous media plays an important role within several areas of science. In many real processes in which the channels undergo continuous expansion and contraction, fluids are subjected not only to shearing but also to stretching. Such examples are the fluid flows through the plate heat exchangers, the porous beds and gaps of rock during crude oil extraction. Typically, pure and/or extensional flow is often required in many practical situations. Most often, we are dealing with the so-called mixed flow, where the deformation rates have parallel and perpendicular components to the flow direction. Solutions of high molecular weight polymers exhibit considerable differences in extensional and shear flow behaviors, and the ratio of extensional viscosity to shear viscosity can be as much as 100 times higher. In case of the flexible polymer solutions through porous media is the increase in flow resistance obtained beyond a critical flow rate. That increase has been attributed to the extensional nature of the flow field in the pores caused by the successive expansions and contractions. Such solutions exhibit strain hardening in extension. In case of the polymer solutions with semi-rigid and rigid chain structures, only the extent strain thinning region can be observed.

W literaturze przedmiotu poświęcono wiele uwagi przepływowi płynów nienewtonowskich przez ośrodki... more W literaturze przedmiotu poświęcono wiele uwagi przepływowi płynów nienewtonowskich przez ośrodki porowate. Najczęściej stosowanymi płynami modelowymi są wodne roztwory polimerów (soli sodowej karboksymetylocelulozy, poliakryloamidu, poli(tlenku etylenu)). W kilku pracach poruszony został również problem przepływu emulsji o/w stabilizowanych niskocząsteczkowymi surfaktantami [Błaszczyk i in., 2017]. Do tej pory nie ma w literaturze informacji dotyczących przepływu przez ośrodki porowate emulsji stabilizowanych polimerami. Przepływ taki występuje między innymi podczas szczelinowania skał (wydobycie ropy naftowej i gazu). Podczas przepływu przez złoże porowate płyn ulega zarówno ścinaniu, jak i rozciąganiu. Wpływ deformacji wzdłużnej na straty ciśnienia ujawnia się głównie w przypadku, gdy w roztworze znajduje się polimer o giętkim łańcuchu (np. poli(tlenek etylenu)). Podczas przepływu roztworów polimerów o łańcuchach półsztywnych (najczęściej są to polielektrolity), do których należy...

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015

Abstract The interactions between anionic and zwitterionic surfactants have been studied on diffe... more Abstract The interactions between anionic and zwitterionic surfactants have been studied on different compounds systems at varied pH, temperature and concentration of anionic surfactant. These systems contained cocamidopropyl betaine, CAPB (C 19 H 38 N 2 O 3 ), and sodium dodecylbenzenesulfonate, SDBS (C 18 H 29 NaO 3 S) forms wormlike micelles in the concentration range of CAPB equal to 0.083 M and SDBS from 0.057 to 0.072 M. The synergism is significant when the concentrations of CAPB in the solution is 0.083 M and SDBS is 0.063 M. The wormlike micellar solutions show a viscoelastic characteristic and at low shear frequencies can be described by the Maxwell model with a single stress relaxation. A pronounced temperature effect on the wormlike micellar structures can be observed by rheological studies. With an increase in temperature, the samples become less structured due to shortening of the micelles. From measurements at zero shear viscosity η 0 , plateau modulus G 0 and relaxation time τ it is evident that the highest values were achieved for 0.063 M SDBS solution. The rheological behavior of the CAPB/SDBS system strongly depends on the pH of a solution, which reflect the pH-dependence of the structural transformation of wormlike micelles. This is caused by the change in the acidity around the carboxylic acid headgroups as a function of pH. Studies of CAPB/SDBS mixtures at constant molar ratio of both surfactants (1.32) revealed that in the range of CAPB from 0.05 to 0.067 M the wormlike micellar network is formed. Above concentration of CAPB 0.067 M the network is completely constituted, however it disappeared completely below 0.05 M.

Procedia Engineering, 2012

The opposed nozzles configuration was used to measure the extensional viscosities of water-in-oil... more The opposed nozzles configuration was used to measure the extensional viscosities of water-in-oil emulsions of dispersed volume fractions varying between 5% and 30%. The two Newtonian type mineral oils with dynamic viscosities about = 0.2182 and 0.0443 [Pa s] were used. All emulsions were prepared with sorbitan monooleate (Span 80) as emulsifier. The results obtained for extensional viscosity of w/o emulsions show that only at very low concentrations of dispersed phase values of the Trouton ratio (Tr = η E /η) are approximately constant (in range of 7-11) while for pure oil are slightly lower (3-6). Additionally, the Trouton ratio is independent of oil phase viscosity in the range of water phase concentration from 5 to 10%. For 20% and higher concentration of disperse phase the extensional viscosity rises with increase of a nozzle diameter. Presented experimental results indicate that the opposing nozzles rheometer used in this work is not a suitable device for measuring the extensional viscosity of viscoplastic fluids.

Advances in Food Rheology and Its Applications, 2017

Many kinds of flows are present in industrial processes among which extensional and shear flows a... more Many kinds of flows are present in industrial processes among which extensional and shear flows are important ones. Measurements of extensional viscosity ηE of liquid foods are important in structural characterization, process and quality control of products, and process modeling and design. These measurements are incomparably more difficult than for the shear viscosity, because of variation of sample dimensions in time when sample is extended at a constant strain rate. This chapter will discuss the methods for measuring the extensional viscosity of fluids with low and high viscosities. Measurements of extensional viscosity are made not only with commercial apparatus but also with special custom constructed devices. Measurements of ηE of fluids having a viscosity lower than 1 Pa·s are particularly troublesome. In addition, typical results of measurements of polymer solutions, emulsions, and other fluids, as well as the theoretical basis related to issue of extensional viscosity will be presented.

Lepkosprê¿yste roztwory kationowych œrodków powierzchniowo czynnych, w których tworz1 siê micele ... more Lepkosprê¿yste roztwory kationowych œrodków powierzchniowo czynnych, w których tworz1 siê micele œlimakowe znajduj1 zastosowanie nie tylko jako dodatki p3ynne przy wydobyciu ropy naftowej i redukcji oporów przep3ywu [1], lecz tak¿e jako œrodki zagêszczaj1ce i p3yny modelowe w procesach biotechnologii [2] oraz w przemyœle kosmetycznym jako uk3ady nadaj1ce produktom odpowiednie w3aœciwoœci organoleptyczne (np. przy produkcji szamponów i ¿elów do mycia cia3a). Celem prezentowanej pracy jest charakterystyka czasu mieszania w roztworach œrodków powierzchniowo czynnych, w których powstaj1 d3ugie prêcikowe struktury micelarne zwane micelami œlimakowymi, dla ró¿nych konstrukcji mieszade3 turbinowych. W wiêkszoœci prac [3, 4] czas mieszania tm przedstawiany jest w postaci zale¿noœci od wspó3czynnika rozpraszania energii: