Dilatational Viscosity Research Articles

Dilatational viscosity of dilute particle-laden fluid interface at different contact angles.

We consider a solid spherical particle adsorbed at a flat interface between two immiscible fluids and having arbitrary contact angle at the triple contact line. We derive analytically the flow field corresponding to dilatational surface flow in the case of a large ratio of dynamic shear viscosities of two fluids. Considering a dilute assembly of such particles we calculate numerically the dependence on the contact angle of the effective surface dilatational viscosity particle-laden fluid interface. The effective surface dilatational viscosity is proportional to the size and surface concentration of particles and monotonically increases with the increase in protrusion of particles into the fluid with larger shear viscosity.

Nanoparticle‐Stabilized Foam for Mobility Control in Enhanced Oil Recovery

AbstractFoam stabilized by a surfactant has been used successfully for mobility control during enhanced oil recovery processes, but the stability of the foam limits its application. Aqueous foams prepared from dispersions of partially hydrophobic silicon dioxide (SiO2) nanoparticles and sodium dodecyl sulfate (SDS) anionic surfactant were studied and the injection behavior of foams stabilized by a solution of SDS or dispersion of SiO2/SDS were analyzed for comparison. Foam stability increased with increasing nanoparticle concentration although the feasibility of producing a foam (foamability) followed the opposite trend. The surface tension and interfacial dilatational rheological properties were affected by the addition of SiO2 nanoparticles. When 0.05 wt % SiO2 was added to the solution of SDS, the system's dilatational elasticity increased significantly, but not the dilatational viscosity. The sweep efficiency to dead end was very small, and the SiO2/SDS foam could displace more residual oil in the dead end than that in the SDS foam. The differential pressure could increase to 0.58 MPa when SDS foam was injected, but for the SiO2/SDS foam it could increase to 1.7 MPa. The SiO2/SDS foam exhibited better profile control performance than that of the SDS foam. When subsequent water was injected for 3.5 pore volumes, the flow rate of the high‐permeability sand pack could still be maintained at 1.0 mL min−1, which suggested that the SiO2/SDS foam had a better resistance to water flushing. Additionally, the foam volume should also be considered, especially for a SiO2 concentration of >1.5 wt %. SiO2/SDS foam can reduce the residual oil saturation clearly, and the enhanced oil recovery and final oil recovery can reach 36.90 and 69.57 %, respectively.

Interpreting attenuation at different excitation amplitudes to estimate strain-dependent interfacial rheological properties of monodisperse contrast microbubbles

Broadband attenuation of ultrasound measured at different excitation pressures being different raises a serious theoretical concern, because the underlying assumption of linear and independent propagation of different frequency components nominally requires attenuation to be independent of excitation. This issue is investigated by examining ultrasound attenuation through a monodisperse lipid coated microbubble suspension measured at four different acoustic excitation amplitudes. We use the attenuation data to determine interfacial rheological properties (surface tension, surface dilatational elasticity and surface dilatational viscosity) of the encapsulation according to three different models. Although different models result in similar rheological properties, attenuation measured at different excitation levels (4–110 kPa) leads to different values for them; the dilatation elasticity (0.56 N/m to 0.18 N/m) and viscosity (2.4×10−8 Ns/m to 1.52×10−8 Ns/m) both decrease with increasing pressure. Numerically simulating the scattered response, nonlinear energy transfer between frequencies are shown to be negligible, thereby demonstrating the linearity in propagation and validating the attenuation analysis. There is a second concern to the characterization arising from shell properties being dependent on excitation amplitude which is not a proper constitutive variable. It is resolved by arriving at a strain-dependent rheology for the encapsulation.

Surface viscosity and Marangoni stresses at surfactant laden interfaces

We calculate here the force on a probe at a viscous, compressible interface, laden with soluble surfactant that equilibrates on a finite time scale. The motion of the probe through the interface drives variations in the surfactant concentration at the interface that in turn leads to a Marangoni flow that contributes to the force on the probe. We demonstrate that the Marangoni force on the probe depends non-trivially on the surface shear and dilatational viscosities of the interface indicating the difficulty in extracting these material properties from force measurements at compressible interfaces.

Influence of surface viscosity on droplets in shear flow

The behaviour of a single droplet in an immiscible external fluid, submitted to shear flow is investigated using numerical simulations. The surface of the droplet is modelled by a Boussinesq–Scriven constitutive law involving the interfacial viscosities and a constant surface tension. A numerical method using Loop subdivision surfaces to represent droplet interface is introduced. This method couples boundary element method for fluid flows and finite element method to take into account the stresses due to the surface dilational and shear viscosities and surface tension. Validation of the numerical scheme with respect to previous analytic and computational work is provided, with particular attention to the viscosity contrast and the shear and dilational viscosities characterized both by a Boussinesq number$B_{q}$. Then, influence of equal surface viscosities on steady-state characteristics of a droplet in shear flow are studied, considering both small and large deformations and for a large range of bulk viscosity contrast. We find that small deformation analysis is surprisingly predictive at moderate and high surface viscosities. Equal surface viscosities decrease the Taylor deformation parameter and tank-treading angle and also strongly modify the dynamics of the droplet: when the Boussinesq number (surface viscosity) is large relative to the capillary number (surface tension), the droplet displays damped oscillations prior to steady-state tank-treading, reminiscent from the behaviour at large viscosity contrast. In the limit of infinite capillary number$Ca$, such oscillations are permanent. The influence of surface viscosities on breakup is also investigated, and results show that the critical capillary number is increased. A diagram$(B_{q};Ca)$of breakup is established with the same inner and outer bulk viscosities. Additionally, the separate roles of shear and dilational surface viscosity are also elucidated, extending results from small deformation analysis. Indeed, shear (dilational) surface viscosity increases (decreases) the stability of drops to breakup under shear flow. The steady-state deformation (Taylor parameter) varies nonlinearly with each Boussinesq number or a linear combination of both Boussinesq numbers. Finally, the study shows that for certain combinations of shear and dilational viscosities, drop deformation for a given capillary number is the same as in the case of a clean surface while the inclination angle varies.

Interfacial Rheological Properties of Contrast Microbubble Targestar P as a Function of Ambient Pressure

In this Technical Note, we determine the interfacial rheological parameters of the encapsulation of the contrast agent Targestar P using ultrasound attenuation. The characteristic parameters are obtained according to two interfacial rheological models. The properties—surface dilatational elasticity (0.09 ± 0.01 N/m) and surface dilatational viscosity (8 ± 0.1E–9 N·s/m)—are found to be of similar magnitude for both models. Contrast microbubbles experience different ambient pressure in different organs. We also measure these parameters as functions of ambient pressure using attenuation measured at different overpressures (0, 100 and 200 mm Hg). For each value of ambient hydrostatic pressure, we determine the rheological properties, accounting for changes in the size distribution caused by the pressure change. We discuss different models of size distribution change under overpressure: pure adiabatic compression or gas exchange with surrounding medium. The dilatational surface elasticity and viscosity are found to increase with increasing ambient pressure.

Giant pH-responsive microgel colloidosomes: preparation, interaction dynamics and stability.

The interactions of two oil droplets grown in the presence of swollen, lightly cross-linked cationic poly(tert-butylamino)ethyl methacrylate (PTBAEMA) microgels was monitored using a high-speed video camera. Three oils (n-dodecane, isopropyl myristate and sunflower oil) were investigated, each in the absence and presence of an oil-soluble cross-linker [tolylene 2,4-diisocyanate-terminated poly(propylene glycol), PPG-TDI]. Adsorption of the swollen microgel particles was confirmed by interfacial tension, interfacial elasticity and dilational viscosity measurements on single pendant oil droplets, and assessment of the oscillatory dynamics for coalescing droplet pairs. Like the analogous bulk emulsions, particle adsorption alone did not prevent coalescence of pairs of giant Pickering emulsion droplets. However, prior addition of surface-active PPG-TDI cross-linker to the oil phase results in the formation of highly stable microgel colloidosomes via reaction with the secondary amine groups on the PTBAEMA chains. Colloidosome stability depended on the age of the oil-water interface. This reflects a balance between the adsorption kinetics of the PPG-TDI cross-linker and the microgel particles, each of which must be present at the interface to form a stable colloidosome. Colloidosome formation was virtually instantaneous in n-dodecane, but took up to 120 s in the case of isopropyl myristate. The impact of an acid-induced latex-to-microgel transition on the interaction of giant colloidosomes (originally prepared at pH 10 using isopropyl myristate) was also studied. This acid challenge did not result in coalescence, which is consistent with a closely-related study (A. J. Morse et al., Langmuir, 2014, 30(42), 12509-12519). No evidence was observed for inter-colloidosome cross-linking, which was attributed to retention of an aqueous film between the adjacent pair of colloidosomes.

Surface properties of adsorption layers formed from triterpenoid and steroid saponins

Abstract Saponins are natural surfactants with non-trivial surface and aggregation properties which find numerous important applications in several areas (food, pharma, cosmetic and others). In the current paper we study the surface properties of ten saponin extracts, having different molecular structure with respect to the type of their hydrophobic fragment (triterpenoid or steroid aglycone) and the number of sugar chains (1 to 3). We found that the triterpenoid saponins Escin, Tea Saponin and Ginsenosides have area per molecule in the range between 0.5 and 0.7 nm2, and the adsorbed molecules are orientated perpendicularly to the interface. The comparison of the experimentally measured surface elasticities with theoretically estimated ones shows that the saponins with very high dilatational and shear elasticities (up to 2000 mN/m) have molecular interaction parameter in the adsorption layers which is above the threshold value for two-dimensional phase transition. In other words, the highly elastic layers are in surface condensed state, due to strong attraction between the adsorbed molecules. Furthermore, these adsorption layers have non-linear rheological response upon expansion and contraction, even at relatively small deformation. Layers from the other studied saponins (steroids and crude mixtures of triterpenoid saponins), which are unable to form strong intermolecular bonds within the adsorption layer, have zero shear elasticity and viscosity and low dilatational elasticity and viscosity, comparable in magnitude to those reported in literature for protein adsorption layers. The comparison of the results, obtained by several independent experimental methods, allowed us to formulate the conditions under which the results from different interfacial rheology tests could be compared, despite the complex non-linear response of the saponin adsorption layers.

Interpreting attenuation at different excitation amplitudes to estimate strain-dependent interfacial rheological properties of lipid-coated monodisperse microbubbles.

Broadband attenuation of ultrasound measured at different excitation pressures being different raises a serious theoretical concern, because the underlying assumption of linear and independent propagation of different frequency components nominally requires attenuation to be independent of excitation. Here, this issue is investigated by examining ultrasound attenuation through a monodisperse lipid-coated microbubble suspension measured at four different acoustic excitation amplitudes. The attenuation data are used to determine interfacial rheological properties (surface tension, surface dilatational elasticity, and surface dilatational viscosity) of the encapsulation according to three different models. Although different models result in similar rheological properties, attenuation measured at different excitation levels (4-110 kPa) leads to different values for them; the dilatation elasticity (0.56 to 0.18 N/m) and viscosity (2.4 × 10(-8) to 1.52 × 10(-8) Ns/m) both decrease with increasing pressure. Numerically simulating the scattered response, nonlinear energy transfer between frequencies are shown to be negligible, thereby demonstrating the linearity in propagation and validating the attenuation analysis. There is a second concern to the characterization arising from shell properties being dependent on excitation amplitude, which is not a proper constitutive variable. It is resolved by arriving at a strain-dependent rheology for the encapsulation. The limitations of the underlying analysis are discussed.

Two-way coupled Reynolds and Rayleigh–Plesset equations for a fully transient, multiphysics cavitation model with pseudo-cavitation

This study presents a physics-based cavitation model solving the coupled Rayleigh–Plesset (RP) and Reynolds (RE) equations in a fully transient environment. Inclusion of the surface dilatational viscosity within the interfacial stress balance of a dynamically growing bubble is discussed at length and detailed physical insight into its mechanism adds significantly to the existing body of literature. A parametric study establishes the importance of the surface dilatational viscosity and values on the order of 10−2 to 10−4 [Ns/m] are shown to establish upper and lower bounds on tensile stresses producing the full and half-Sommerfeld-like solutions respectively. Interactions between rotational speed and eccentricity ratio are elucidated with the overall effect of increasing surface dilatational viscosity shown to be de-stabilizing.

Effects of ambient hydrostatic pressure on the material properties of the encapsulation of an ultrasound contrast microbubble.

Ultrasound contrast microbubbles experience widely varying ambient blood pressure in different organs, which can also change due to diseases. Pressure change can alter the material properties of the encapsulation of these microbubbles. Here the characteristic rheological parameters of contrast agent Definity are determined by varying the ambient pressure (in a physiologically relevant range 0-200 mm Hg). Four different interfacial rheological models are used to characterize the microbubbles. Effects of gas diffusion under excess ambient pressure are investigated in detail accounting for size decrease of contrast microbubbles. Definity contrast agent show a change in their interfacial dilatational viscosity (3.6 × 10(-8) Ns/m at 0 mm Hg to 4.45 × 10(-8) Ns/m at 200 mm Hg) and interfacial dilatational elasticity (0.86 N/m at 0 mm Hg to 1.06 N/m at 200 mm Hg) with ambient pressure increase. The increase results from material consolidation, similar to such enhancement in bulk properties under pressure. The model that accounts for enhancement in material properties with increasing ambient pressure matches with experimentally measured subharmonic response as a function of ambient pressure, while assuming constant material parameters does not.

A Study of Relationship Between Oil-Water Interfacial Dilational Rheology and Oil Recovery of Alkaline Flooding

AbstractIn order to find out the influence of dilational rheology on chemical flooding systems, the dilational rheology of Zhuangxi crude oil/NaOH solutions interface was investigated by DSA100 interfacial dilatational rheometer (KRÜSS, Germany). The results show that the alkaline system, which can enhance oil recovery, mainly depends on its interfacial dilational rheology, rather than interfacial tension. The greater the interfacial dilational elasticity, the higher the oil recovery is. The greater the interfacial dilational viscosity, the lower the oil recovery is. The conclusion is consistent with the change of displacement pressure in the macro displacement experiment and the change of sweep efficiency in the microscopic displacement experiment.

Effect of partially hydrolyzed polyacrylamide on emulsification stability of wastewater produced from polymer flooding

Abstract In this work, the effect of partially hydrolyzed polyacrylamide (HPAM) on the oil–water interfacial properties of produced water from polymer flooding (PWPF) was investigated. In addition, this study investigated the effects of three fiocculants (polyaluminium chloride PAC, cationic polymer FO4800SH, and nonionic polymer 402) on the stability of PWPF. The experimental results demonstrate that the addition of HPAM enhances the emulsion stability by increasing viscosity, zeta potential, interfacial tension and interfacial dilational viscoelasticity. The molecular weight and hydrolysis degree of HPAM have no significant influences on these properties. The stability of PWPF can be enhanced by increasing HPAM concentration. Dependency of frequency and concentration was observed for the interfacial dilational viscoelasticity. With the addition of HPAM, the dilational viscoelasticity not only increases with HPAM concentration but runs through a maximum at a concentration of 300 mg/L. As the oscillating frequency increases, the dilational modulus and dilational elasticity increase but the dilational viscosity decreases. The three flocculants can reduce the stability of the emulsion by considerably decreasing the absolute value of zeta potential of oil droplets. FO4800SH has a greater ability than PAC and 402 to separate oil from the emulsion. But the demulsification efficiencies of the three flocculants are not satisfactory because of the presence of HPAM residue. Further research is needed to find more efficient methods to achieve excellent performance of oil–water separation towards PWPF.

On the role of surface rheology in a magnetohydrodynamic swirling flow

The original coupling between the surface rheology of a liquid metal surface and a supporting annular Couette magnetohydrodynamic (MHD) flow is theoretically and numerically investigated in this paper, in the general layout of the classical annular viscometer, as developed by Mannheimer and Schechter [“An improved apparatus and analysis for surface rheological measurements,” J. Colloid Interface Sci. 32, 195–211 (1970)]. The purely hydrodynamic interplay between the main azimuthal flow (induced by a rotating floor) and the secondary overturning flow (generated by centrifugation) is found to be strongly affected by both surface viscous shear and surface viscous dilatation. When the flow is subjected to an outer vertical magnetic field, the impact of varying interface boundary conditions (through the surface shear and dilatational viscosities) at the gas/liquid interface profoundly alters the MHD flow topology. Particularly, when centrifugation competes with electromagnetic effects, advection of the main flow by the secondary flow is proved to affect significantly the core MHD flow, leading to a variety of atypical MHD flow patterns.

Effect of Glyphosate Isopropylamine on the Surface Tension and Surface Dilational Rheology Properties of Polyoxyethylene Tallow Amine Surfactant

In order to develop the substitutes for polyoxyethylene tallow amine (POEA), the understanding the interaction of glyphosate isopropylamine and POEA is essential. The surface behaviors of POEA and POEA in the presence of 1 wt% glyphosate isopropylamine have been investigated at the air-water interface by the drop shape analysis method. The influences of surface tension, dilational frequency, and bulk concentration on the surface properties were expounded. The experiment results show that the adsorption films of POEA behave elastic in nature at low bulk concentration. With increasing in bulk concentration, the dilational modulus, dilational elasticity, and dilational viscosity pass through a maximum value, the phase angle increase monotonically. These phenomena can be attributed to the diffusion-exchange process between the bulk and the interface. The addition of 1 wt% glyphosate isopropylamine significantly influences on the POEA surface tension and dilational properties. The dilational modulus, dilational elasticity, and dilational viscosity obvious decrease in general, and the values of phase angle significant change after the addition of 1 wt% glyphosate isopropylamine. Glyphosate isopropylamine and POEA form a new complex in the solution and the surface activity and surface dilational properties of complex is different from POEA.

Mathematical models for the acoustic response of a solids-loaded encapsulated bubble.

A method of active acoustic resonance interference spectroscopy is introduced for estimation of bubble properties. A modified form of Rayleigh-Plesset equation for forced oscillation of either a single free bubble or elastic shell encapsulated microbubble with attached solids loading is solved by the regular perturbation method for steady oscillatory solutions as a result of small amplitude acoustic excitation by a point sinusoidal oscillator. A model for the total pressure field at an acoustic receiver in an incompressible liquid is then solved by the regular perturbation method. Closed-form analytical solutions are found for pressure power at the acoustic receiver as a function of the excitation frequency and strength; the properties of the bubble, liquid, and encapsulating shell; and the geometry of the active monitoring system. The receiver pressure power exhibits a maximum due to bubble resonance and a minimum due to destructive interference between source and bubble response pressure fields at higher excitation frequencies. The inverse problem is solved to derive unique closed-form analytical estimators for bubble equilibrium size, attached solids mass loading, and encapsulating layer dilatational viscosity as a function of the frequencies of the fundamental resonance maximum, interference minimum, second harmonic maximum total average acoustic power, monitoring system, and phase properties.

Effective surface dilatational viscosity of highly concentrated particle-laden interfaces.

The effective surface dilatational viscosity is calculated of a flat interface separating two immiscible fluids laden with half-immersed monodisperse rigid spherical non-Brownian particles in the limit of high particle concentration. The derivation is based upon the facts that (i) highly concentrated particle arrays in a plane form a hexagonal structure and (ii) the dominant contribution to the viscous dissipation rate arises in the thin gaps between neighboring particles.

Effect of starch particles on foam stability and dilational viscoelasticity of aqueous-foam

Surface dilational rheological behavior and foam stability of starch/surfactant mixed solutions were studied at different starch concentrations and constant surfactant concentration. The results show that dilational viscoelasticity modulus, dilational elasticity modulus and dilational viscosity modulus increase with the concentration of starch particles. Foam stability increases with dilational viscoelasticity. Foam strength also increases with starch concentration. Starch particles play a positive effect on foam stability and dilational viscoelasticity and the effect becomes more significant as drainage proceeds. Film pictures indicate that the film with 20% (by mass) starch particles is thicker than that without starch. Starch particles gather in Plateau border and resist drainage, making the foam more stable.

Interfacial dynamic and dilational rheology of polyelectrolyte/surfactant two-component nanoparticle systems at air–water interface

The interfacial characteristics of nanoparticles and consequent inter-particle interactions at the interface are poorly understood. In this work, the interfacial dynamic and corresponding dilational surface rheology of self-assembled polyelectrolyte/surfactant nanoparticles at the air–water interface are characterized. The nanoparticles are prepared from dodecyltrimethylammonium (DTAB) and poly (sodium 4-styrene-sulfonate) (PSS) by mixing them in aqueous solution. The interfacial dynamic characteristics have been carried out by comparing the surface pressure with the dilational rheological response of these nanoparticles at interface. The results indicate that this type of nanoparticles can adsorb at the interface forming a nanoparticle monolayer, which leads to the surface tension decreased markedly. The dependence of surface pressure on time shows the instability and disassembly process of nanoparticles at the interface. On the basis of these observations, it is proposed that the nanoparticles undergo a dynamic process that interface induced nanoparticles disassembly into DTAB/PSS complexes. The presence of PSS in the subphase can promote the process of nanoparticles disassembly. A transition point in dilational elasticity and viscosity response of the nanoparticles versus oscillation frequency further validate the micro dynamic process of nanoparticles and the formation of polyelectrolyte/surfactant complex monolayer at the interface.

Competitive adsorption of the protein hydrophobin and an ionic surfactant: Parallel vs sequential adsorption and dilatational rheology

The competitive adsorption of the protein HFBII hydrophobin and the anionic surfactant sodium dodecyl sulfate (SDS) is investigated in experiments on parallel and sequential adsorption of the two components. The dynamic surface tension and the surface storage and loss dilatational moduli are determined by the oscillating bubble method. A new procedure for data processing is proposed, which allows one to collect data from many different runs on a single master curve and to determine more accurately the dependence of the dilatational elasticity on the surface pressure. Experiments on sequential adsorption are performed by exchanging the HFBII solution around the bubble with an SDS solution. Experiments with separate thin foam films bring additional information on the effect of added SDS. The results indicate that if HFBII has first adsorbed at the air/water interface, it cannot be displaced by SDS at any concentration, both below and above the critical micellization concentration (CMC). In the case of parallel adsorption, there is a considerable difference between the cases below and above the CMC. In the former case, SDS cannot prevent the adsorption of HFBII at the interface, whereas in the latter case adsorption of HFBII is absent, which can be explained with hydrophilization of the hydrophobin aggregates by the SDS in the bulk. The surface dilatational elasticity of the HFBII adsorption layers markedly decreases in the presence of SDS, but it recovers after washing out the SDS. With respect to their dilatational rheology, the investigated HFBII layers exhibit purely elastic behavior, the effect of dilatational viscosity being negligible. As a function of surface tension, the elasticity of the investigated interfacial layers exhibits a high maximum, which could be explained with the occurrence of a phase transition in the protein adsorption layer.