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The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquid–liquid interfaces. Two cases have been studied, NPs smaller than the interfacial thickness, and NPs greater than the interfacial thickness.

The model is based on the molecular dynamics (MD) simulation in addition to phase field (PF) method, through which the discrete model of particles motion is superimposed on the continuum model of fluids which is a new ide a in numerical modeling. The liquid–liquid interface is modeled using the diffuse interface model.

For NPs smaller than the interfacial thickness, the results obtained show that the concentration gradient of one fluid in the other gives rise to a hydrodynamic drag force that drives the NPs to agglomerate at the interface. Whereas, for spherical NPs greater than the interfacial thickness, the results show that such NPs oscillate at the interface which agrees with some experimental studies.

The results are important in the field of numerical modeling, especially that the model is general and can be used to study different systems. This will be of great interest in the field of studying the behavior of NPs inside fluids and near interfaces, which enters in many industrial applications.

The idea of superimposing the molecular dynamic method on the PF method is a new idea in numerical modeling.

The purpose of this paper is to analyze two-dimensional steady-state Rayleigh–Bénard convection within rectangular enclosures in different aspect ratios filled with yield stress fluids obeying the Herschel–Bulkley model.

In this study, a numerical method based on the finite element has been developed for analyzing two-dimensional natural convection of a Herschel–Bulkley fluid. The effects of Bingham number Bn and power law index n on heat and momentum transport have been investigated for a nominal Rayleigh number range (5 × 10³ < Ra < 10⁵), three different aspect ratios (ratio of enclosure length:height AR = 1, 2, 3) and a single representative value of nominal Prandtl number (Pr = 10).

Results show that the mean Nusselt number Nu¯ increases with increasing Rayleigh number due to strengthening of convective transport. However, with the same nominal value of Ra, the values of Nu¯ for shear thinning fluids n < 1 are greater than shear thickening fluids n > 1. The values of Nu¯ decrease with Bingham number and for large values of Bn, Nu¯ rapidly approaches unity, which indicates that heat transfer takes place principally by thermal conduction. The effects of aspect ratios have also been investigated and results show that Nu¯ increases with increasing AR due to stronger convection effects.

This paper presents a numerical study of Rayleigh–Bérnard flows involving Herschel–Bulkley fluids for a wide range of Rayleigh numbers, Bingham numbers and power law index based on finite element method. The effects of aspect ratio on flow and heat transfer of Herschel–Bulkley fluids are also studied.

The purpose of this paper is to analyze the effects of complex boundary conditions on natural convection of a yield stress fluid in a square enclosure heated from below (uniformly and non-uniformly) and symmetrically cooled from the sides.

The governing equations are solved numerically subject to continuous and discontinuous Dirichlet boundary conditions by Galerkin’s weighted residuals scheme of finite element method and using a non-uniform unstructured triangular grid.

Results show that the overall heat transfer from the heated wall decreases in the case of non-uniform heating for both Newtonian and yield stress fluids. It is found that the effect of yield stress on heat transfer is almost similar in both uniform and non-uniform heating cases. The yield stress has a stabilizing effect, reducing the convection intensity in both cases. Above a certain value of yield number Y, heat transfer is only due to conduction. It is found that a transition of different modes of stability may occur as Rayleigh number changes; this fact gives rise to a discontinuity in the variation of critical yield number.

Besides the new numerical method based on the finite element and using a non-uniform unstructured grid for analyzing natural convection of viscoplastic materials with complex boundary conditions, the originality of the present work concerns the treatment of the yield stress fluids under the influence of complex boundary conditions.

The purpose of this paper is to focus on the advanced solution of the parametric non-linear model related to the Rayleigh-Benard laminar flow involved in the modeling of natural thermal convection. This flow is fully determined by the dimensionless Prandtl and Rayleigh numbers. Thus, if one could precompute (off-line) the model solution for any possible choice of these two parameters the analysis of many possible scenarios could be performed on-line and in real time.

In this paper both parameters are introduced as model extra-coordinates, and then the resulting multidimensional problem solved thanks to the space-parameters separated representation involved in the proper generalized decomposition (PGD) that allows circumventing the curse of dimensionality. Thus the parametric solution will be available fast and easily.

Such parametric solution could be viewed as a sort of abacus, but despite its inherent interest such calculation is at present unaffordable for nowadays computing availabilities because one must solve too many problems and of course store all the solutions related to each choice of both parameters.

Parametric solution of coupled models by using the PGD. Model reduction of complex coupled flow models. Analysis of Rayleigh-Bernard flows involving nanofluids.

The purpose of this paper is to compute flow effects of the transition from adherence-to-slip in two-dimensional flows, for a polymer melt obeying a memory-integral viscoelastic equation, in isothermal and non-isothermal cases.

Temperature dependence is expressed by Arrhenius and William-Landel-Ferry models. A coupling approach is defined. For the dynamic equations, the Stream-Tube Method (STM) is used with finite differences in a mapped rectangular domain of the real domain, where streamlines are parallel and straight. STM avoids particle-tracking problems and allows simple formulae to evaluate stresses resulting from the constitutive equation. For the temperature field, a finite-element method is carried out to solve the energy equation in the real domain.

The approach avoids numerical problems arising with classical formulations and proves to be robust and efficient. Large elasticity levels are attained without convergence and refinement difficulties that may arise close to the “stick-slip” transition section. The method highlights the role of temperature conditions and reveals interesting differences for the ducts considered.

The results of the study are of interest for polymer processing where slip at the wall can be encountered, in relation with the physical properties of the materials.

The paper presents a simple approach that limits considerably numerical problems coming from stick-slip boundary conditions and avoids particle-tracking. Results are obtained at flow rates encountered in industrial conditions.

This paper aims to synthesize new screen-printing ink formula based on new derivatives of azo thiadiazol disperse dyes and evaluate their characteristics after being printed on polyester fabric substrates.

New dispersed dyes based on 1, 3, 4-Thiadiazole derivatives (dyes 1 and 2) were prepared and confirmed by different analyses, infrared (IR), mass and nuclear magnetic resonance (NMR) spectroscopy, and then formulated as colored materials in the screen-printing ink formulations. Printing pastes containing the prepared dyestuffs and other ingredients were used for printing polyester using screen-printing or traditional printing. The characteristics of printed polyester fabric substrates were measured by color measurements such as a*, b*, L*, C*, E, Ho, R% and color strength, as well as light, washing, crock and alkali perspiration fastness, and finally, the depth of penetration was evaluated.

The prepared 1, 3, 4-Thiadiazole derivatives (dyes 1 and 2) were obtained from the reaction of 5,5’-(1,4-phenylene)bis(1,3,4-Thiadiazole-2-amine) with resorcinol and m-toluidine as a coupling component. The suitability of the prepared dyestuffs for silk screen-printing on polyester fabrics has been investigated. The prints obtained from a formulation containing dye 1 possess high color strength as well as good overall fastness properties if compared to those obtained using dye 2.

The method of synthesis of the new dyestuffs and screen-printing ink provides a simple and practical solution to prepare some new heterocyclic disperse azo dyes, and they are formulated in the screen-printing inks for printing on a polyester fabric substrate.

The prepared disperse dyes based on 1,3,4-Thiadiazole derivatives (dyes 1 and 2) could be used in textile printing of polyester on an industrial scale.

This study aims to show the dyeing behaviour of polyester fabrics using four novel heterocyclic disperse dyes.

The four dyes were synthesized based on 5, 5'-(1, 4-phenylene) bis (1, 3, 4-thiadiazol-2-amine) as a diazonium compound. The UV/Vis absorption spectroscopic data of these disperse dyes while dyeing polyester fabrics were investigated. Following this, the dyeing properties of these dyes on polyester fabrics were investigated under acid condition.

The results showed that increasing the dyeing temperature from 80°C to 100°C led to an increase in dye uptake for all dyes, but further increases of the temperature to 130°C led to higher dye uptake for dye 3 as the dye exhaustion increased by about 50% from 55.9% to 91.4%.

This study is important as it introduces new dyes for the dyeing of polyethylene terephthalate (PET) fibres with colours that range from yellowish orange to bluish yellow and scarlet red and all with excellent brightness, levelness and depth of shade.

Introduction The corrosion of iron has been extensively studied in various media. In nitric acid solutions, the corrosion of iron is much faster than in other mineral acids at comparable concentrations. This is attributed to an autocatalytic process involving some nitrogen oxides, nitrous acid and/or some iron complexes. At high nitric acid concentrations, passivation of iron takes place. The factors affecting the dissolution and the passivation processes are not fully understood. The effect of various inhibitors on the corrosion of iron in acid media has been studied. Thus Ammar et al. have studied the passivation of iron and the effect of some anions, e.g. Br− and I− on the passive film. The effect of amides as inhibitors for iron in nitric acid has been reported by Fouda and Gouda. These authors have found that the corrosion process is controlled by the reaction of amides with HNO3 and not by the surface reaction. The effect of aniline and some aminobenzoic acids on the rate of corrosion of iron has been reported. The present work is aimed at examining the efficiencies of some aniline substitutes as corrosion inhibitors for the corrosion of iron in concentrated nitric acid solution.

This study aims to propose that the corrosion resistance of the neat epoxy coating can be further enhanced by incorporating reinforcing agents.

Chitosan, silica and their hybrid compound were used to study the subject of corrosion resistance of epoxy coating systems. This work used 3.5 Wt.% NaCl solution as the electrolyte, and electrochemical impedance spectroscopy (EIS) was used to investigate the electrochemical behaviour of the studied coating systems. Standard and accelerated states were used without and with scratch on the coating layer.

It was found that the impedance value of composite coating incorporated with the hybrid compound was significantly higher at 10¹⁰ Ω after 14 days of exposure in both testing states. The breakpoint frequency (f_b) determination also proves with large capacitive region at low-to-high frequency of impedance plots corresponding to the high corrosion resistance.

The hybrid compound consisting of chitosan as organic biopolymer and silica as inorganic material, respectively, served as a promising reinforcing agent for composite coating as a promising corrosion inhibitor. Different states of EIS measurement were used which are standard (without scratch) and accelerated (with scratch) states associated with the f_b values.

This study aims to prepare some disperse dyes based on pyrazole derivatives and fully evaluate their use as azo-disperse dyes linked with pyrazolo[1,5-a] pyrimidine. This study aims to prepare dye polyester fabric at different conditions (pH and time) at a depth of 4% using a high-temperature pressure process in water.

The disperse dyes were created by dissolving enaminone and pyrazole derivatives in glacial acetic acid and fusing sodium acetate at reflux for 6 h. The chemical structure of the produced dye was studied using elemental analysis, Fourier-transform infrared spectroscopy, 1H NMR and 13C NMR spectroscopic analytical methods. The dyeing of Dispersed dyes 14–16 on polyester under diverse conditions was comprehensively investigated in this work.

The prepared Organic dyes 14–16 were found to be highly functional and suitable for this type of dyeing technique. High color strength is possessed by the materials dyed with Disperse dyes 14–16. Even in low alkaline conditions, these dyes exhibited a strong affinity for polyester fabric, changing just little in response to pH changes. The hue of the dyed polyester samples varied from beige to reddish brown and yellowish brown because of the coupler moieties.

This study is important because it offers novel dyes that may be used to dye polyethylene terephthalate fibers that exhibit remarkable brightness and levelness. It also offers a viable solution for creating a variety of colors in polyester fabrics.