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Purpose: The purpose of this study is to investigate the effects of the shear-thinning viscoelastic behavior of the surrounding matrix on droplet deformation by weakly compressible smoothed particle hydrodynamics (WC-SPH). Also, the effect of the presence of another droplet is examined. Design/methodology/approach: A modified consistent weakly compressible SPH method is proposed. After code verification, a complete parameter study is performed for a drop under the simple shear flow of a Giesekus liquid. The investigated parameters are 0.048≤Ca ≤ 14.4, 0.1≤c ≤ 10, 0.04≤De ≤ 10, 0≤α ≤ 1 and 0.12≤Re ≤ 12. Findings: It is demonstrated that the rheological behavior of the surrounding fluid could dramatically affect the droplet deformation. It is shown that the droplet deformation is increased by increasing Re and Ca. In contrast, the droplet deformation is decreased by increasing a, De and polymer content. Also, it is indicated the presence of another droplet could drastically affect the flow field, and the primary stress difference (N1) is resonated between two droplets. Originality/value: The main originality of this paper is to introduce a new consistent WC-SPH algorithm. The proposed method is very versatile for tackling the shear-thinning viscoelastic multiphase problems. Furthermore, a complete parameter study is performed for a drop under the simple shear flow of Giesekus liquid. Another novelty of the current paper is studying the effect of the presence of a second droplet. To the best of the authors' knowledge, this is performed for the first time. [ABSTRACT FROM AUTHOR]

Highlights • Higher maximum speeds are achieved with the log-conformation formulation. • Fluids with polymeric additives achieve thinner films than Newtonian fluids. • The Giesekus model behaves better than the Phan–Thien–Tanner model in blade coating. Abstract Previous studies have demonstrated the benefits of the log-conformation formulation to model viscoelastic fluids; it increases stability at high Weissenberg numbers and ensures that the conformation tensor remains positive-definite. Many studies have applied the log-conformation tensor formulation to benchmark cases; however, relatively few studies investigate using the formulation on more complex flows. In this paper, we extend the log-conformation formulation to the manufacturing-relevant flow of blade coating. We first verify the log-conformation formulation on the benchmark problem of flow past a cylinder using the finite element method, and then apply it to the blade-coating process, in which a viscoelastic fluid entrained by a moving substrate passes under a blade at a constant web speed. We investigate various rheological effects and the resulting film thickness for the blade-coating problem, and compare the results from the log-conformation formulation to those of the original stress formulation. We show that the log-conformation formulation agrees well with other established methods, and also increases the maximum achievable web speed in the blade-coating problem. [ABSTRACT FROM AUTHOR]

This article elucidates viscoelastic fractional fluid flow along with homogeneous-heterogeneous reactions. Non-integer derivatives are important for the systems having hereditary behavior as they depend on the past conditions along with the local conditions. Viscoelastic fluids keep memory of old deformations and their behavior is related to these deformations. The fractional derivatives are more adequate in predicting the characteristics of viscoelastic fluids than the ordinary derivatives. In this paper we have examined characteristics of fractional homogeneous-heterogeneous reactions with variable concentrations of both the reactant species. Flow is induced by the variable moving surface. Diffusion coefficients of reactants and auto catalyst are of comparable size. For better understanding of hereditary properties, non integer Caputo time derivatives have been incorporated in mathematical formulation of the flow regime. Unsteady motion of a magnetohydrodynamic incompressible viscoelastic fluid is governed by highly nonlinear fractional partial differential equations. Flux conditions are imposed on the chemical species at the boundary. Governing flow equations with suitable initial and boundary conditions have been discretized using finite difference-finite element scheme. Proposed numerical scheme is flexible for the solution of non-linear flow problems. Skin friction coefficients are calculated for fractional viscoelastic model. Flow field is demonstrated for different values of involved parameters. The acquired results revealed that with the increase of fractional exponent α concentration of chemical specie decreases for the final time t = 2 . It is also noted that concentration gradients of chemical specie increase with the increase of α at both the boundaries of flow configuration. In literature no such result exits with non integer Caputo fractional derivatives. Various viscoelastic flows particularly in chemical, plastics and polymer industries can be modeled in a similar manner. [ABSTRACT FROM AUTHOR]

Highlights • Numerical study of the dynamics of nearly incompressible viscoelastic fluid membranes. • Investigation of the effects of viscoelasticity on the dynamics. • Higher values of the relaxation time enhance the necking of the stretched membranes. • Higher values of the relaxation time facilitate the onset of buckling and wrinkling. Abstract This work presents a novel numerical investigation of the dynamics of free-boundary flows of viscoelastic liquid membranes. The governing equation describes the balance of linear momentum, in which the stresses include the viscoelastic response to deformations of Maxwell type. A penalty method is utilized to enforce near incompressibility of the viscoelastic media, in which the penalty constant is proportional to the viscosity of the fluid. A finite element method is used, in which the slender geometry representing the liquid membrane, is discretized by linear three-node triangular elements under plane stress conditions. Two applications of interest are considered for the numerical framework provided: shear flow, and extensional flow in drawing processes. [ABSTRACT FROM AUTHOR]

This work investigates the unsteady electroosmotic slip flow of viscoelastic fluid through a parallel plate micro-channel under combined influence of electroosmotic and pressure gradient forcings with asymmetric zeta potentials at the walls. The generalized second grade fluid with fractional derivative was used for the constitutive equation. The Navier slip model with different slip coefficients at both walls was also considered. By employing the Debye-Hückel linearization and the Laplace and sin-cos-Fourier transforms, the analytical solutions for the velocity distribution are derived. And the finite difference method for this problem was also given. Finally, the influence of pertinent parameters on the generation of flow is presented graphically. [ABSTRACT FROM AUTHOR]

In this paper, a three-field finite element stabilized formulation for the incompressible viscoelastic fluid flow problem is tested numerically. Starting from a residual based formulation, a non-residual based one is designed, the benefits of which are highlighted in this work. Both formulations allow one to deal with the convective nature of the problem and to use equal interpolation for the problem unknowns σ − u − p (deviatoric stress, velocity and pressure). Additionally, some results from the numerical analysis of the formulation are stated. Numerical examples are presented to show the robustness of the method, which include the classical 4: 1 planar contraction problem and the flow over a confined cylinder case, as well as a two-fluid formulation for the planar jet buckling problem. [ABSTRACT FROM AUTHOR]

Highlights: [•] We study the deformation of soft systems in fluids under unbounded shear flow. [•] The study is done with a finite element method based code for viscoelastic fluids. [•] To track the interface, a finite element method is defined on it. [•] Deformed shape of drops and elastic particles are nearly ellipsoidal. [•] Results on elastic particles in viscoelastic fluids are shown for the first time. [Copyright &y& Elsevier]

Highlights: [•] Peristaltic transport of viscoelastic fluids through a non-uniform porous channel has been studied. [•] Pressure for small values of the averaged flow rate reduces with increasing permeability parameter. [•] Pressure decreases with increasing first fractional parameter whereas opposite with second parameter. [•] An increase in non-uniformity constant increases friction force. [•] A decrease in permeability serves to reduce the magnitude of the trapped secondary boluses. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the numerical simulation of three-dimensional time-dependent viscoelastic free surface flows using the Upper-Convected Maxwell (UCM) constitutive equation and an algebraic explicit model. This investigation was carried out to develop a simplified approach that can be applied to the extrudate swell problem. The relevant physics of this flow phenomenon is discussed in the paper and an algebraic model to predict the extrudate swell problem is presented. It is based on an explicit algebraic representation of the non-Newtonian extra-stress through a kinematic tensor formed with the scaled dyadic product of the velocity field. The elasticity of the fluid is governed by a single transport equation for a scalar quantity which has dimension of strain rate. Mass and momentum conservations, and the constitutive equation (UCM and algebraic model) were solved by a three-dimensional time-dependent finite difference method. The free surface of the fluid was modeled using a marker-and-cell approach. The algebraic model was validated by comparing the numerical predictions with analytic solutions for pipe flow. In comparison with the classical UCM model, one advantage of this approach is that computational workload is substantially reduced: the UCM model employs six differential equations while the algebraic model uses only one. The results showed stable flows with very large extrudate growths beyond those usually obtained with standard differential viscoelastic models. [Copyright &y& Elsevier]

Abstract: This paper presents a new stabilized finite element method for incompressible viscoelastic fluids. A three-field formulation is developed wherein Oldroyd-B model is coupled with the mass and momentum conservation equations for an incompressible viscous fluid. The variational multiscale (VMS) framework is employed to develop a stabilized formulation for the coupled momentum, continuity and stress equations. Based on the new stabilized method a family of linear and higher-order triangle and quadrilateral elements with equal-order velocity–pressure–stress fields is developed. Stability and convergence property of the various elements is studied and optimal rates are attained in the norms considered. The method is applied to some benchmark problems and accuracy and computational economy of the formulation is investigated for various flow conditions. [ABSTRACT FROM AUTHOR]

The governing equations of the flow of an oldroyd-B fluid are discretized using the finite element method. To overcome the convective nature of the momentum equation, the Galerkin/Least-Squares Finite Element Method (GLS/FEM) is used while the Discrete Elastic–Viscous Stress-Splitting (DEVSS) method is used to overcome the instability due to the absence of diffusion in the constitutive equations. The discretized equations are implemented on a hybrid system between the Graphics Processing Unit (GPU) architecture using Compute-Unified-Device-Architecture (CUDA) and a multi-core CPU. The implementation is applied successfully to simulate the blood flow in abdominal aortic aneurysm. To accelerate application performance on the GPU several optimized approaches are adopted. The most significant approach is the coloring technique that is used to assemble the global matrix. Numerical experiments show that the hybrid CPU-GPU implementation has a 26 time speedup over the multi-core CPU implementations. [ABSTRACT FROM AUTHOR]