Concentration Dependence Of Viscosity Research Articles

Characteristics of synovial trihybrid nanofluid activation energy and Marangoni convective flow: A Computational framework of local thermal non-equilibrium

The impact of nonlinear heat source and activation energy on magnetized Synovial trihybrid nanofluid Marangoni convective flow across a sheet combining two viscosity models is investigated in this study. Heat sources, activation energy, and conditions of local thermal non-equilibrium (LTNE) are all considered in the modelling. Based upon energy equations, the LTNE model provides unique heat transport for both liquid and solid phases. This leads to the utilization of different temperature profiles for the fluid and solid phases in this work. A trihybrid fluid is created by combining the basic fluid blood with MWCNT (multi-wall carbon nanotubes), SWCNT (single-wall carbon nanotubes) and sliver nanoparticle. This study significant potential in several fields. The effects of parameters on friction between joints are examined, which aids in the analysis of the lubricant nature of Synovial trihybrid nanofluid. A significant finding of the current work is that the thermal profiles decrease with higher values of the Concentration-dependent viscosity parameter, but the velocity profile increases. An increase in the inter-phase heat transfer characteristic raises the liquid phase's thermal profile while lowering the solid phase's thermal profile.

Prediction of the Bubble Growth Behavior by Means of the Time-, Temperature-, Pressure- and Blowing Agent Concentration-Dependent Transient Elongational Viscosity Function of Polymers.

Bubble growth processes are highly complex processes, which are not only dependent on the foaming process parameters (temperature, pressure and blowing agent concentration) but also on the type and structure of the polymer used. Since the elongational viscosity at the bubble wall during bubble growth also depends on these influencing factors, the so-called transient elongational viscosity plays a key role in describing the gas bubble growth behavior in polymer melts. The model-based description of the transient elongational viscosity function is difficult due to its dependence on time, Hencky strain and strain rate. Therefore, representative viscosities or shear viscosity models are usually used in the literature to predict the bubble growth behavior. In this work, the transient equibiaxial elongational viscosity function at the bubble wall during bubble growth is described holistically for the first time. This is achieved by extending the so-called molecular stress function (MSF) model by superposition principles (temperature, pressure and blowing agent concentration) and by using the elongational deformation behavior (Hencky strain and strain rate) at the bubble wall during the initial, and thus viscosity-driven, bubble growth process. Therefore, transient uniaxial elongational viscosity measurements are performed and the non-linear MSF model parameters of the two investigated polymers PS (linear polymer chains) and PLA (long-chain branched polymer chains) are determined. By applying the superposition principles and by changing the strain mode parameter to the equibiaxial case in the MSF model, the transient equibiaxial viscosity master curve is obtained and used to describe the bubble growth process. The results show that the extended MSF model can fully predict the transient equibiaxial elongational viscosity function at the bubble wall during bubble growth processes. The bubble growth behavior over time can then be realistically described using the defined transient equibiaxial elongational viscosity function at the bubble wall. This is not possible, for example, with a representative viscosity and therefore clearly demonstrates the influence and importance of knowing the transient deformation behavior that prevails at the bubble wall during bubble growth processes.

Anomalous Concentration Dependence of Viscosity: Hidden Role of Cross-Correlations in Aqueous Electrolyte Solutions.

The viscosity of aqueous electrolyte solutions exhibits well-known composition-dependent anomalies that show certain definitive trends and universal features. The viscosity of LiCl and NaCl solutions increases with concentration in a monotonic fashion, while solutions of KCl, RbCl, and CsCl exhibit a more complex behavior. Here, the viscosity first decreases and then increases with increasing concentration, with a rather broad minimum at intermediate concentrations (ca. 1-3 m). To unearth the origin of such puzzling behavior, we carried out detailed molecular-level analyses by interrogating the exact Green-Kubo expression of viscosity in terms of the stress-stress time correlation function (SS-TCF). The total SS-TCF can be decomposed into a collection of three self- and three cross-SS-TCFs arising from the three constituent components (water, cations, and anions). Mode coupling theory (MCT) analysis for the friction on ions and the viscosity of the solution suggests the possible importance of two-particle static and time-dependent cross-correlations between water and the ions. We calculate the viscosity and other dynamical properties for all five electrolyte (LiCl, NaCl, KCl, RbCl, and CsCl) solutions over a range of concentrations, using two models of water (SPC/E and TIP4P/2005). The total viscosity derives non-negligible contributions from all of the terms. The cross-correlations are found to be surprisingly large and seen to play a hidden role in the concentration dependence. However, the importance of cross-correlations is often not discussed. Our study leads to a theoretical understanding of the microscopic origin of the observed anomalies in the composition dependence of viscosity across all five electrolytes.

A second-order fully-balanced structure-preserving variational discretization scheme for the Cahn–Hilliard–Navier–Stokes system

We propose and analyze a structure-preserving space-time variational discretization method for the Cahn–Hilliard–Navier–Stokes system. Uniqueness and stability for the discrete problem is established in the presence of concentration-dependent mobility and viscosity parameters by means of the relative energy estimates and order optimal convergence rates are established for all variables using balanced approximation spaces and relaxed regularity conditions on the solution. Numerical tests are presented to demonstrate the proposed method is fully practical and yields the predicted convergence rates. The discrete stability estimates developed in this paper may also be used to analyse other discretization schemes, which is briefly outlined in the discussion.

Global well-posedness and convergence to equilibrium for the Abels-Garcke-Grün model with nonlocal free energy

We investigate the nonlocal version of the Abels-Garcke-Grün (AGG) system, which describes the motion of a mixture of two viscous incompressible fluids. This consists of the incompressible Navier-Stokes-Cahn-Hilliard system characterized by concentration-dependent density and viscosity, and an additional flux term due to interface diffusion. In particular, the Cahn-Hilliard dynamics of the concentration (phase-field) is governed by the aggregation/diffusion competition of the nonlocal Helmholtz free energy with singular (logarithmic) potential and constant mobility. We first prove the existence of global strong solutions in general two-dimensional bounded domains and their uniqueness when the initial datum is strictly separated from the pure phases. The key points are a novel well-posedness result of strong solutions to the nonlocal convective Cahn-Hilliard equation with singular potential and constant mobility under minimal integral assumption on the incompressible velocity field, and a new two-dimensional interpolation estimate for the L4(Ω) control of the pressure in the stationary Stokes problem. Secondly, we show that any weak solution, whose existence was already known, is globally defined, enjoys the propagation of regularity and converges towards an equilibrium (i.e., a stationary solution) as t→∞. Furthermore, we demonstrate the uniqueness of strong solutions and their continuous dependence with respect to general (not necessarily separated) initial data in the case of matched densities and unmatched viscosities (i.e., the nonlocal model H with variable viscosity, singular potential and constant mobility). Finally, we provide a stability estimate between the strong solutions to the nonlocal AGG model and the nonlocal Model H in terms of the difference of densities.

Revealing foam stability for cationic and zwitterionic triethylsilyl-containing surfactants

A fundamental understanding of surfactant structure–property–performance relationships will inform the design of next-generation alternatives to perfluoroalkyl substances (PFAS) in aqueous film-forming foams. This manuscript describes the synthesis, solution properties, and foam stability of novel triethylsilyl-containing surfactants, which elucidated the influence of the hydrophilic head group on critical micelle concentration (CMC), surface tension, and foam stability. Photocatalyzed hydrosilylation of triethylsilane and N,N-dimethyl allylamine yielded N,N-dimethyl-3-(triethylsilyl)propane-1-amine. Subsequent functionalization with either propane sultone or bromoethane afforded zwitterionic sulfobetaine surfactant, 3-(dimethyl(3-(triethylsilyl)propyl)ammonio)propane-1-sulfonate (TESDMAPS) and cationic quaternary ammonium surfactant, and N-ethyl-N,N-dimethyl-3-(triethylsilyl)propane-1-ammonium bromide (TESDMABr), respectively. Dynamic light scattering and cryo-transmission electron microscopy (TEM) characterized micelle size and shape in solutions above the CMC. Surface tensiometer analysis determined minimum TESDMAPS and TESDMABr solution surface tensions of 37.7 and 35.9 mN/m, respectively. Molecular dynamics simulations related this decrease in surface tension to a larger average interfacial area of 88 Å2 per TESDMABr molecule compared to 66 Å2 per TESDMAPS molecule. Steady-shear rheological measurements showed consistent exponential viscosity-scaling relationships between TESDMAPS and TESDMABr solutions ≤ 30 wt. %. Above this concentration, TESDMAPS displayed solution viscosities greater than TESDMABr, and a mixture of surfactants provided an intermediate concentration dependent viscosity scaling. Dynamic foam analysis revealed TESDMABr foams displayed longer 25% foam drainage times than TESDMAPS. The oscillatory rheology of TESDMABr solutions demonstrated solid-like solution behavior at low shear rates. Finally, polarized light-imaging rheology highlighted the formation of birefringent structures in TESDMABr solutions under shear. For the first time, this work relates solution viscoelasticity from shear-induced surfactant assembly to foam stability with implications on fluorine-free, next-generation, fire-fighting foams.

Sucrose transport inside the phloem: Bridging hydrodynamics and geometric characteristics

In plants, the delivery of the products of photosynthesis is achieved through a hydraulic system labeled as phloem. This semi-permeable plant tissue consists of living cells that contract and expand in response to fluid pressure and flow velocity fluctuations. The Münch pressure flow theory, which is based on osmosis providing the necessary pressure gradient to drive the mass flow of carbohydrates, is currently the most accepted model for such sucrose transport. When this hypothesis is combined with the conservation of fluid mass and momentum as well as sucrose mass, many simplifications must be invoked to mathematically close the problem and to resolve the flow. This study revisits such osmotically driven flows by developing a new two-dimensional numerical model in cylindrical coordinates for an elastic membrane and a concentration-dependent viscosity. It is demonstrated that the interaction between the hydrodynamic and externally supplied geometrical characteristic of the phloem has a significant effect on the front speed of sucrose transport. These results offer a novel perspective about the evolutionary adaptation of plant hydraulic traits to optimize phloem soluble compounds transport efficiency.

A Bingham Plastic Fluid Solver for Turbulent Flow of Dense Muddy Sediment Mixtures

We have developed and tested a numerical model for turbulence resolving simulations of dense mud–water mixtures in oscillatory bottom boundary layers, based on a low Stokes number formulation of the two-phase equations. The resulting non-Boussinesq equation for the fluid momentum is coupled to a transport equation for the mud volumetric concentration, giving rise to a volume-averaged fluid velocity that is non-solenoidal, and the model was implemented as a new compressible flow solver. An oscillating pressure gradient force was implemented in the correction step of the standard semi-implicit method for pressure linked equations (SIMPLE), for consistency with the treatment of other volume forces (e.g., gravity). The flow solver was further coupled to a new library for Bingham plastic materials, in order to model the rheological properties of dense mud mixtures using empirically determined concentration-dependent yield stress and viscosity. We present three direct numerical simulation tests to validate the new MudMixtureFoam solver against previous numerical solutions and experimental data. The first considered steady flow of Bingham plastic fluid with uniform concentration around a sphere, with Bingham numbers ranging from 1 to 100 and Reynolds numbers ranging from 0.1 to 100. The second considered the development of turbulence in oscillatory bottom boundary layer flow, and showed the formation of an intermittently turbulent layer with peak velocity perturbations exceeding 10 percent of the freestream flow velocity and occurring at a distance from the bottom comparable to the Stokes boundary layer thickness. The third considered the effects of density stratification due to resuspended sediment on turbulence in oscillatory bottom boundary layer flow with a bulk Richardson number of 1×10−4 and a Stokes–Reynolds number of 1000, and showed the formation of a lutocline between 20 and 40 Stokes boundary layer depths. In all cases, the new solver produced excellent agreement with the previous results.

On the steady-state concentration and hydrodynamic fields close to a rotating hemispherical electrode with concentration dependent viscosity and diffusivity

On the steady-state concentration and hydrodynamic fields close to a rotating hemispherical electrode with concentration dependent viscosity and diffusivity

Numerical Experiments for Surfactant Infiltration in the Vadose Zone to Demonstrate Concentration-Dependent Capillarity, Viscosity, and Sorption Characteristics

Surfactants (i.e., solutes that reduce the surface tension of water) exist in the subsurface either naturally or are introduced to the subsurface due to anthropogenic activities (e.g., agricultural purposes, environmental remediation strategies). Surfactant-induced changes in surface tension, contact angle, density, and viscosity alter the water retention and conduction properties of the vadose zone. This research numerically investigates the effects of surfactants in the vadose zone by comparing the flow and transport of three different surfactant solutions, namely butanol, ethanol, and Triton X-100. For each surfactant case, surfactant-specific concentration-dependent surface tension, contact angle, density, and viscosity relationships were incorporated by modifying a finite element unsaturated flow and transport code. The modified code was used to simulate surfactant infiltration in the vadose zone at residual state under intermittent boundary conditions. The modelling results show that all three surfactant solutions led to unique and noteworthy differences in comparison to the infiltration of pure water containing a conservative tracer. Results indicate that surfactant infiltrations led to complex patterns with reduced vertical movement and enhanced horizontal spreading, which are a function of concentration-dependent surface tension, density, contact angle, viscosity and sorption characteristics. The findings of this research will help understanding the effects of surfactant presence in the subsurface on unsaturated flow and its possible links to future environmental problems.

Advances in the modelling of concentration-dependent relative viscosity data for nanofluids by introducing the Dispersion Factor

The viscosity ratio (relative viscosity) of a nanofluid to its base liquid is related to the nanoparticle volume fraction by various developed theoretical and empirical equations. However, the theoretical framework used up to now is often inadequate for modelling experimental data. Now, a new parameter denoted as the Dispersion Factor (DF) is proposed to advance the accurate modelling of relative viscosities of nanofluids dependent on nanoparticle volume fraction. Literature data of TiO2, γ-Al2O3and SiO2nanofluids have been selected and subjected to our new theoretical treatment using the Chen equation adapted with the Dispersion Factor to model the relative viscosity in relation to the nanoparticle volume fractions.A much better agreement with the experimental data has been obtained. The value of DF that is identified by the mathematical modelling of relative viscosity data reflects the comprehensive effect of particle size, shape and chemical composition on the interactions between the nanoparticle and the base liquid on the one hand, and solvated nanoparticle and nanoparticle interactions on the other hand. The DF parameter may present a possible tool that can be used to tailor and tune the nanofluid design to meet specific application requirements.

Therapeutic phosphorodiamidate morpholino oligonucleotides: Physical properties, solution structures, and folding thermodynamics

Elucidating the structure-function relationships for therapeutic RNA mimicking phosphorodiamidate morpholino oligonucleotides (PMOs) is challenging due to the lack of information about their structures. While PMOs have been approved by the US Food and Drug Administration for treatment of Duchenne muscular dystrophy, no structural information on these unique, charge-neutral, and stable molecules is available. We performed circular dichroism and solution viscosity measurements combined with molecular dynamics simulations and machine learning to resolve solution structures of 22-mer, 25-mer, and 30-mer length PMOs. The PMO conformational dynamics are defined by the competition between non-polar nucleobases and uncharged phosphorodiamidate groups for shielding from solvent exposure. PMO molecules form non-canonical, partially helical, stable folded structures with a small 1.4- to 1.7-nm radius of gyration, low count of three to six base pairs and six to nine base stacks, characterized by -34 to -51kcal/mol free energy, -57 to -103kcal/mol enthalpy, and -23 to -53kcal/mol entropy for folding. The 4.5- to 6.2-cm3/g intrinsic viscosity and Huggins constant of 4.5-9.9 are indicative of extended and aggregating systems. The results obtained highlight the importance of the conformational ensemble view of PMO solution structures, thermodynamic stability of their non-canonical structures, and concentration-dependent viscosity properties. These principles form a paradigm to understand the structure-properties-function relationship for therapeutic PMOs to advance the design of new RNA-mimic-based drugs.

On the estimation of equivalent conductivity of electrolyte solutions: The effect of relative static permittivity and viscosity

The effect of a concentration-dependent relative static permittivity (RSP) and viscosity on the predictions of the equivalent conductivity models is studied. The full version and simplified version of the mean spherical approximation models along with four Debye-Hückel-Onsager (DHO) based equivalent conductivity models are used to predict the equivalent conductivity of nine 1:1 aqueous electrolyte solutions at 25°C. Three of the DHO based models have been developed in this study by combining the electrophoretic and relaxation effects that have been previously presented in the literature. To investigate the effect of RSP on the equivalent conductivity predictions, we have used three empirical RSP models along with the solvent's RSP. It has been shown that using a concentration-dependent RSP reduces the deviation of equivalent conductivity predictions from the experimental data. We have also investigated the effect of a concentration-dependent viscosity on the equivalent conductivity predictions. Our observations show that using a concentration-dependent viscosity sometimes improves and sometimes worsens the predictions.

Axial complexes of Sn(IV)-tetra(4-sulfophenyl)porphyrin with azorubine in aqueous media: Fluorescent probes of local viscosity and pH indicators

A triad (Az-SnP-Az) consisting of two azorubine ligands (Az) axially bonded to the sulfo-derivative of Sn(IV)-tetraphenylporphyrin [SnP(OH)2] has been synthesized. The triad structure is optimized by quantum chemical calculations and confirmed by a complex of physicochemical methods. The spectral-luminescent properties of the triad and its components in aqueous media have been studied. The sensitivity of the photophysical characteristics of the triad to the concentration-dependent viscosity of the solution has been studied on a model system (binary solvent glycerol-water). It has been established that the resulting triad has the properties of a molecular rotor and exhibits high sensitivity to local viscosity at the Az and SnP absorption maxima. The ability to tune the wavelength of the radiation, allows configuring the created “molecular rotor” to monitor the local viscosity for each specific case.

Mixed-dimensional multi-scale poroelastic modeling of adipose tissue for subcutaneous injection.

Subcutaneous injection of therapeutic monoclonal antibodies (mAbs) has gained increasing interest in the pharmaceutical industry. The transport, distribution and absorption of mAbs in the skin after injection are not yet well-understood. Experiments have shown that fibrous septa form preferential channels for fluid flow in the tissue. The majority of mAbs can only be absorbed through lymphatics which follow closely the septa network. Therefore, studying drug transport in the septa network is vital to the understanding of drug absorption. In this work, we present a mixed-dimensional multi-scale (MDMS) poroelastic model of adipose tissue for subcutaneous injection. More specifically, we model the fibrous septa as reduced-dimensional microscale interfaces embedded in the macroscale tissue matrix. The model is first verified by comparing numerical results against the full-dimensional model where fibrous septa are resolved using fine meshes. Then, we apply the MDMS model to study subcutaneous injection. It is found that the permeability ratio between the septa and matrix, volume capacity of the septa network, and concentration-dependent drug viscosity are important factors affecting the amount of drug entering the septa network which are paths to lymphatics. Our results show that septa play a critical role in the transport of mAbs in the subcutaneous tissue, and this role was previously overlooked.

Transport and distribution of biotherapeutics in different tissue layers after subcutaneous injection

The subcutaneous injection is the main route of administration for monoclonal antibodies (mAbs) and several other biotherapeutics due to the patient comfort and cost-effectiveness. However, their transport and distribution after subcutaneous injection is poorly understood. Here, we exploit a three-dimensional poroelastic model to find the biomechanical response of the tissue, including interstitial pressure and tissue deformation during the injection. We quantify the drug concentration inside the tissue. We start with a single-layer model of the tissue. We show that during the injection, the difference between the permeability of the solvent and solute will result in a higher drug concentration proportional to the inverse permeability ratio. Then we study the role of tissue layered properties with primary layers, including epidermis, dermis, subcutaneous (SQ), and muscle layers, on tissue biomechanical response to injection and drug transport. We show that the drug will distribute mainly in the SQ layer due to its lower elastic moduli. Finally, we study the effect of secondary tissue elements like the deep fascia layer and the network of septa fibers inside the SQ tissue. We use the Voronoi tessellation algorithm to create random geometry of the septa network. We show how drugs accumulate around these tissue components as observed in the experimental SQ injection. Next, we study the effect of injection rate on drug concentration. We show how higher injection rates will slightly increase the drug concentration around septa fibers. Finally we demonstrate how the concentration dependent viscosity will increase the concentration of biotherapeutics in the direction of septa fibers.

PH indicator and rotary fluorescent properties of the Sn(IV)-octaetylporphyrin-(BODIPY)2 triad

A triad of two 1,3,5,7-tetramethyl-8-(4-hydroxyphenyl)BODIPY ligands (BODIPY) axially linked to Sn(IV)-octaethylporphyrin [Sn(BODIPY)2OEtP] is synthesized. The structure of the triad is optimized by quantum chemical calculations and confirmed by a combination of physicochemical methods. The spectral luminescent properties of the triad and its components in DMF solution are studied. Using a model system of the DMF-glycerol binary solvent, the sensitivity of the photophysical characteristics of the triad to the concentration-dependent viscosity of the solution, as well as to the addition of acids and alkalis, is studied. Sn(BODIPY)2OEtP photoexcitation leading to photoinduced energy transfer from donor fragments of BODIPY to the porphyrinate acceptor is observed. As a result, upon excitation of the triad at λex = 490 nm both BODIPY fluorescence and porphyrin fluorescence are recorded. When the triad is excited at λex = 400 nm, the fluorescence of the porphyrin increases compared to the initial Sn(IV)-octaethylpophyrin. This energy transfer, which depends on both the mobility of the medium and its acidity, provides the Sn(BODIPY)2OEtPtriad with the properties of a molecular rotor, a pH indicator and very high photostability (resistance to photobleaching), as well as antibacterial activity against the Staphylococcusaureus ATCC strain.

Significance of concentration-dependent viscosity on the dynamics of tangent hyperbolic nanofluid subject to motile microorganisms over a non-linear stretching surface

The communication describes a theoretical framework for tangent hyperbolic fluid of nano-biofilm due to an extending or shrinking sheet that comprises a stagnation point flow, chemical reaction with activation energy, and bioconvection of gyrotactic microorganisms. The varying transport features due to dynamic viscosity, thermal conductivity, nano-particle mass permeability and microbe organisms diffusivity are taken into account for the novelty of this work. The inspiration is developed to enhance heat transfer. A set of leading partial differential equations is formed along with appropriate boundary constraints. Using similarity transformations, the basic formulation is transitioned into non-linear differential equations. To produce observational data, the shooting technique and Runge-Kutta fourth order method are employed. The coding of numerical scheme is developed in Matlab script. The visual representation of the effects of diverse fluid transport properties and distinctive parameters on speed, temperature, concentration and motile density are evaluated. The velocity become faster when the parameters omega , lambda , epsilon and V_0 are enhanced. Brownian motion, thermal conductivity, heat generation as well as thermophoresis factors all strengthen the temperature distribution, however the nano-particle concentration profile is enhanced as the nano-particle mass conductivity variable, activation energy as well as the thermophoresis variable are boosted. The microorganism density improves significantly when the microorganism diffusivity factor increases. The skin friction, Sherwood number, Nusselt number and motile density number decline against the incremented transport parameters.

Concentration-dependent viscosity effect on magnetonano peristaltic flow of Powell-Eyring fluid in a divergent-convergent channel

The viscosity of fluids has an essential role in blood circulation through veins and arteries. So, this paper focuses on the influences of dependent-viscosity on the peristaltic flow of Powell-Eyring fluid in a divergent-convergent channel. Viscosity is supposed to vary with the temperature and concentration fluid. A theoretical relation to the concentration-dependent viscosity is introduced mathematically for the Powell-Eyring nanofluid for the first time in our literature. The formulation of the model contains a highly nonlinear system of PDEs that converted to ODEs by physical assumptions to low Reynolds number and long wavelength. A semi-analytical solution was obtained in different theoretical cases of the divergent-convergent channel using the generalized differential transform method (GDTM). Results for velocity profile, temperature distribution, and concentration distribution as well as extra stress tensor profile versus various values flow parameters have been constructed. Results show that the variation parameters of viscosity α, and β can control with flow velocity at each part of channel wall making them improve/get better the blood circulation in veins (Circulatory system). Furthermore, the concentration-dependent viscosity parameter increases the temperature distribution of fluid while it declines the nanoparticle diameter of fluid.

Observation of order-disorder phase transition in sheared nanofluids

We have investigated the flow properties of a nanofluid (NF) suspension (oleic acid-coated Fe3O4 in kerosene) under a sheared system. A distinct cooperative flow mediated by the gelation temperature (Tg) leading to an order-disorder transition state is evidenced within a definite and short range of temperatures, around 86 °C. Further, the particle size and concentration-dependent viscosity vs. temperature studies have moderated the phase transition phenomena of the NFs dispersion. The findings provide a unique visco-elastic behavior of the nanofluid to gel state follows first-order –type phase transition, which has technological applications as heat engines.