Linear viscoelastic region is important to investigate material properties. We investigated boundary of linear viscoelasticity for simple shear flows with various time functions of shear strain. We used Phan-Thien and Tanner (PTT) model and Giesekus model in order to extract the linearity criterion. We determined critical strain (γc) as a function of dimensionless number such as De or Wi and the nonlinear

In this study a theoretical study is carried out on the collision of two rod-like particles suspended in Newtonian fluid under a shear flow. The length of the particle is fixed at 2 µm while the diameter is varied so that the aspect ratio (length/diameter) varies from 1 to 20. Liquid viscosity is changed from 0.01 to 1 Pa·s. The Brownian motion is considered to be negligible. Both hydrodynamic and

The current paper is focused on analyzing the flow of viscoplastic fluid in a cavity that is driven by the two walls. The Lattice Boltzmann method (LBM) is used to solve the discrete Boltzmann equation. To represent the stress-strain rate relationship of viscoplastic fluids, the Bingham Papanastasiou constitutive model is considered. Cavity flow filled with Bingham fluids is considered for validating

In this study a theoretical study is carried out on the binary collision of round-sided disks (RSD) suspended in a Newtonian fluid under a simple shear flow. RSD is composed of a disk part and a half-torus part which circumscribes the side of the disk. The diameter of the disk is fixed at 2 µm while the thickness and the half-torus size are varied so that the aspect ratio varies from 0.13 to 0.288

The gloss defect on a glossy surface is one of the surface defects to be found on injection-molded products. In this paper, the effects of the filling and packing stages on surface gloss are investigated. Based on observations, a generation mechanism of gloss difference is proposed. The difference of the surface gloss can be explained by the replication of the shrinking polymer surface represented

In this study, the localization behavior of multiwalled carbon nanotubes (MWCNTs) was investigated in the ternary blends based on PC/SAN/PMMA (60/30/10). The major interest was focused on the effects of two different SANs having AN contents of 24 and 32 wt.% (SAN24 and SAN32, respectively) and PMMA on the phase structure of the composites. It was found that the spreading of PMMA around SAN32 was pronounced

In the rheological characterization of non-Newtonian fluids in a steady torsional shear flow using a parallel-plate geometry, there is a need to correct the shear stress at the rim for non-Newtonian behavior. Solving the governing torsional flow equation inversely by Tikhonov regularization using experimental torque vs. rim shear rate data is the most scientific method for obtaining the model independent

Creating a reliable and accurate Red Blood Cell (RBC) aggregation model for small and midsize arteries and veins is still an active research subject with more in focus with a multi-scale approach including mesoscale effects. Better understanding the RBC aggregation requires a multi-phase and multi-scale approach for simulating blood with Newtonian and non-Newtonian parts. In our proposed work, viscosity

In this work, nanocomposites of polypropylene (PP)/polystyrene (PS)/multi-walled carbon nanotube (MWCNT) were prepared by the sonochemical polymerization of styrene in the presence of PP and MWCNT. This procedure offered a composite (PP-g-PS/MWCNT) having a unique phase structure in which MWCNTs are distributed in both phases of PP and PS, which is contrary to the typical observations in the composites

The transient, axisymmetric squeeze flow of the non-Newtonian shear thinning material between finite disks is studied numerically. The fluid between disks is assumed to follow the Carreau-Bird model. Two disks approach each other at a constant velocity while no-slip boundary condition is assumed. The time dependent simulation shows the effect of fluid nonlinearity, flow parameters and geometric aspect

This paper presents a method for measuring the viscosity of generalized Newtonian fluid directly in flows generated by flat-blade turbine impellers, which are commonly used for moderate mixing and dispersion. A flat-blade turbine with four blades is defined as a model system and analyzed through numerical simulations with experimental verification. Carbopol 940 solution, a high viscosity non-Newtonian

Flow features of rheologically complex fluids inside curved microchannels should be meaningfully scrutinized for effective mixing, sorting, and manipulation of nano- and micro-sized colloids or particles. In this study, a particle streak velocimetry method with coordinate transformation is incorporated to depict experimentally the axial velocity profiles of Newtonian and non-Newtonian (Bird-Carreau

Linear stability of a viscoelastic fluid obeying the Walters’ B model is analytically and numerically investigated in the entrance region of a plane channel formed between two parallel plates. The plates are compliant and obey the two degree-of-freedom von Karman solid model. Having obtained the base-flow velocity profiles using the boundary-layer theory, their vulnerability to infinitesimally small

In this paper, we present a study of the dripping properties of polycarbonate (PC) modified with combinations of earth metal salts of inorganic sulfur, potassium perfluorobutane sulfonate (Rimar); non-halogenated flame retardant additives, potassium diphenyl sulfone-3-Sulfonate (KSS); and block co-polymers-polytetrafluoroethylene encapsulated with styrene acrylonitrile resin (T-SAN). Measurements of

To extend the period of decomposition and property degradation of polybutylene adipate terephthalate (PBAT) mulching film for long-term use, PBAT was compounded with polyethylene mixture (LDPE: LLDPE = 15:85), calcium carbonate, and illite. PBAT mulching films were prepared using a blown film extrusion process with 80 mm diameter blowing die. To improve mechanical properties and processability of the

In order to investigate how particle aggregation affects tensile mechanical performance of composite, a ductile biopolymer (poly(caprolactone)) was melt-compounded with CaCO3 particles over a wide concentration range from 10 to 60 wt.%. The aggregation of CaCO3 particles in poly(caprolactone) (PCL) is investigated depending on particle concentration and surface modification (with stearic acid (2.5

To effectively control the mixing of target materials inside microfluidic devices, the Dean flow features of generalized-Newtonian Bird-Carreau (BC) fluids in curved rectangular channels are theoretically investigated, as a passive technique. Governing equations coupled with the Cauchy momentum equation and the BC model are solved using the finite volume scheme with a semi-implicit method for pressure-linked

To explore the drag-reducing characteristics of turbulent channel flows with surfactant additive at relatively high Reynolds number from the perspectives of energy spectrum and multi-scale resolution, the two-dimensional fluctuation velocity fields of turbulent channel flows with/without surfactant additive at Reynolds number of Reτ = 590 obtained by large eddy simulation are decomposed by two-dimensional

Novel gelatin-containing polymer hydrogels that can be used as mucoadhesive delivery systems were developed. Poly(acrylic acid) hydrogels were modified by copolymerizing gelatin as adhesion promoter, to improve the adhesion to the mucus layer and the synthesized copolymer of acrylic acid (AA) and methacrylated gelatin (GelMA) were designated as P(AA-co-GelMA). The pH-sensitivity and the mucoadhesive

The rheological properties and gelation kinetics of corn starch (CS)/bovine serum albumin (BSA) blends were investigated using the mass ratio of [CS]/[BSA] of 0, 0.5, 1, 2, and 3. The results from the temperature ramp and time sweep tests within linear viscoelastic regime showed a decrease in the gelation temperature (Tgel) and gelation time (tgel) of the BSA with increasing the mass ratio of [CS]/[BSA]

To effectively discriminate changes in blood samples, RBCs aggregation and blood viscosity should be evaluated independently and simultaneously. In this study, by setting two syringe pumps for delivering two fluids (blood sample and reference fluid) at stepwise varying flow rates, RBCs aggregation (AI) and viscosity (µBlood) are sequentially measured by quantifying image intensity of blood flows ()

The multi-chain slip-spring (MCSS) model is a coarse-grained molecular model developed for efficient simulations of the dynamics of entangled polymers. In this study, we examined the model for the viscoelasticity of polyisoprene (PI) melts, for which the data are available in the literature. We determined the conversion factor for the molecular weight from the fitting of the molecular weight dependence

Dynamic oscillatory shear flow has been widely used to investigate viscoelastic material functions. In particular, small amplitude oscillatory shear (SAOS) tests have become the canonical method for characterizing the linear viscoelastic properties of complex fluids based on strong theoretical background and plenty of experimental results. Recently, there has been increasing interest in the use of

The flow of a bi-disperse polymer melt through a hyperbolic contraction is simulated using the recently proposed Rolie-Double-Poly constitutive model (Boudara et al., 2019). This simplified tube model takes account of the nonlinear coupling between the dynamics of the long and short-chains in a bi-disperse blend, in particular it reproduces the enhancement of the stretch relaxation time that arises

The extensional rheology of polymer melts and dilute polymer solutions has been extensively examined through experiments and theoretical predictions. However, a systematic study of the extensional rheology of polymer solutions in the semidilute regime, in terms of examining the effects of concentration and molecular weight, has not been carried out so far. Previous experimental studies of the shear

Common features of complex fluids include yield stress, thixotropy and elasticity. A comprehensive constitutive model attempts to effectively predict flow responses dominated by such characteristics. Nevertheless, when constructing a constitutive model that deals with yield stress fluids one must try to preserve the fundamental characteristics of a yield stress. This paper explores the static and energy

Understanding the vortex dynamics in polymer solutions is one of keys for the flow control in a wide range of polymer-related material processing applications. Vortex is generated due to the viscoelasticity of polymer solution, even if no vortex formation is expected under Newtonian flow conditions. In addition, the chaotic vortices generated in viscoelastic fluids have been recently exploited to mix

In this work, we study different rheological and thermal phenomena present during laser sintering of two polystyrene (PS) particles using fully resolved numerical simulations. In our analysis, we varied the laser power, the initial temperature and the thermal convection coefficient, used different rheological descriptions for the flow behavior and in addition studied the effect of the substrate (used

The direct imaging of flow induced microstructural changes in complex fluids can have advantages over the use of scattering methods, since localized phenomena can be observed directly and more mechanistic insights can be obtained. This is useful in particular for materials with hierarchical or multiscale structures such as aggregated dispersions. Rheoconfocal instruments are ideally suited for this

Low molecular weight, amphiphilic diblock copolymers in selective solvent exhibit complex phase behavior and macroscopic properties that affect the processing and application of these materials. The mechanical properties of the crystalline phases seen in concentrated solutions are dependent on nanoscale structure and sample history. The goal of this study is to characterize macroscopic properties and

Breakup of fluid threads is omnipresent in nature and highly relevant for technical processes such as atomization, printing, coating, or spinning. We discuss how to control the filament lifetime of shear-thinning, viscoelastic fluids during uniaxial extension without affecting their shear viscosity. Two commercial acrylic thickeners differing with respect to the co-polymerized hydrophobic monomers

Many researches have studied the viscoelasticity of cellulose/ionic liquid solutions through the conventional scaling rules which assume the monodisperse polymer. However, they are not suitable for cellulose since natural polymers such as cellulose have molecular weight distribution. In this paper, dynamic rheological behaviors of 1-ethyl-3-methyl imidazolium acetate solutions dissolving three kinds

Laminar flow of a viscoelastic fluid obeying the linear simplified Phan-Thien/Tanner model (LPTT) is numerically studied in a planar channel partially obstructed by a cosinusoidal constriction. Based on published data (Tammadon-Jahromi et al., 2011) there is no excess pressure drop for this particular fluid when flowing through an orifice-plate. Numerical results obtained using OpenFoam software at

Resin transfer molding (RTM) is a manufacturing process that uses liquid resin to saturate a fiber preform placed in a closed mold cavity. For robust fabrication of the composite, fiber preform needs to be completely impregnated with polymer resin during mold filling. Hence, the understanding of resin flow and void formation in RTM is very important to design the mold and processing conditions for

We report a dispersion state of concentrated multiwalled carbon nanotube (MWCNT) suspensions depending on their iterative milling process. The rheological properties of concentrated suspensions prepared with different milling times were measured using a Couette-typed rotation rheometer, and their electrical characteristics were investigated via an LCR meter. The relationships of the rheological and

In this work, the impact dynamics of high-viscous nanofluid droplets onto a solid surface has been investigated experimentally by means of high-speed camera visualization technique. We dispersed various nanoparticles (multiwall carbon nanotube (MWCNT), nano-graphene, and nano-graphite powder) into high-viscous base fluid (epoxy resin) to obtain the stable and homogenous nanofluids without surfactant

Peristaltic flow of a thixotropic fluid obeying the Moore model is numerically studied using the multiple-relaxation-time lattice Boltzmann method (MRT-LBM). Converged results could be obtained in a planar two-dimensional channel at large Reynolds numbers for arbitrary wavelengths and amplitude ratios for nonzero Reynolds numbers. It is shown that depending on the Reynolds number and the parameters

Carbon nanotubes (CNTs) are used as nanofillers in polymer nanocomposites to improve the properties of a matrix polymer because of their excellent properties. However, CNTs tend to aggregate due to the strong van der Waals force between CNTs. To solve the problem, surface-modified CNTs with hydrophilic polymers, such as polyvinyl pyrrolidone (PVP) and polystyrene sulfonate (PSS), were employed. Polystyrene

The quantification of coating adhesion on substrates is an important technology that has recently received much attention in automotive industry because the adhesion characteristics of automotive paints have a great influence on color and appearance of automobiles. Here, we present a robust and precise method for quantifying the coating adhesion of automotive paints on flat substrates using new microgap

The suspensions and emulsions are important products and raw materials for various industrial production and processing branches. The knowledge concerning the rheological properties of such substances is of key importance for many manufacturing processes. Many dependences can be found within the literature but there is lack of model that takes into account the influence of inner phase concentration

Polyolefin blend type thermoplastic elastomers (TPEs) were prepared via melt blending method in a twin screw extruder by using isotactic polypropylene (i-PP), three different styrene-olefin triblock copolymers (SEBS-1 and SEBS-2 having a styrene content of 30 wt.% and 60 wt.%, respectively and SEEPS having a styrene content of 30 wt.%) and paraffinic oil. Composition-dependent and time-dependent viscoelastic

It is of great importance to understand and predict screw characteristics (SC) during the single screw extrusion process for the extruder design and the operation optimization. In order to simulate SC effectively, we introduce the concept of a partial rotational fraction for a partial periodic unit of helical geometry in the metering section of the single screw extruder. In this work, the partial rotational

Two different shapes of spherical- and flake-like soft-magnetic carbonyl iron (CI) microparticles were dispersed in silicone oil to prepare magnetorheological (MR) fluids. The magnetic-field dependent rheological behaviors of the MR fluids were scrutinized focusing on their shape effect. Saturation magnetization of the flake-shaped CI was obtained to be slightly lower than that of spherical-shaped

First-harmonic MAOS moduli were demonstrated experimentally using monodisperse linear polystyrene (PS) solutions at different concentrations. Two first-harmonic intrinsic nonlinearities are asymptotic deviations from two linear viscoelastic moduli and obtained in medium amplitude oscillatory shear (MAOS) regime. Master curves of first-harmonic MAOS moduli for PS solutions provided novel information

The objective of this study is to elucidate the relation between the results of ball drop tests and the residual stress distribution of an injection-compression molded part. To improve the ball drop property, a high impact material and a robust manufacturing process were employed. For the application to the transparent plastic window, it is of great importance to increase the impact strength of plastic

Inelasticity effects on the migration of a drop and pairwise interaction of drops in a simple shear flow are studied using a finite-difference front-tracking method. The Carreau-Yasuda model is used to adjust the shear-thinning behavior of fluids. Results showed that drop deformation and migration rate of drops in an inelastic system are smaller than those in a Newtonian one. It was revealed that inelasticity

A blade-free planetary mixer provides an effective and rapid mixing of cohesive powders due to its powerful centrifugal agitation capability to produce a swirling flow pattern in a mixing vessel. Despite its popular use in the powder processing industry, the dynamics and characteristics of blade-free planetary mixing are still not well understood because of a lack of experimental and numerical studies

In order to investigate the effects of clay particles on the coalescence of oil droplets, a typical head-on experiment was carried out. The coalescence of two oil drops containing clay was observed depending on the clay types. The influence of clay on the coalescence of oil droplets is successfully distinguished from the coalescence of pure oil droplets. When two oil droplets make direct contact, pure

Elemental sulfur has been introduced to the suspensions of polycarbonate (PC), poly(styrene-co-acrylonitrile) (SAN) and multi-walled carbon nanotubes (MWCNT). A particular interest was focused on the effect of sulfur diradicals on the rheological properties and phase structure of the sonicated composites. The melt viscosities, elasticities, and relaxation moduli of the PC/SAN/MWCNT composites were

Characterization of viscoelastic properties of the human thigh skin can be utilized in many medical or engineering applications such as a surgical extension of the thigh skin, a tissue engineering, and a finite element modeling of thigh skin in a sitting posture. This study aims to determine the effective short- and long-term shear moduli of posterior thigh skin using ramp-relaxation test in a sitting

One of the newest viscoelastic RANS turbulence models for drag reducing flows with polymer additives is studied considering different rheological properties. A finitely extensible nonlinear elastic-Peterlin (FENE-P) constitutive model is used to describe the viscoelastic effect of the polymer solutions and the \(k - \varepsilon - \overline {{v^2}} - f\) turbulence framework is applied for turbulence

In the present paper, analytical solutions for thermal convection of the Finitely Extensible Nonlinear Elastic model with Peterlin’s closure (FENE-P) in isothermal slits and tubes are presented by considering the viscous dissipation effects for the first time. Temperature distributions are derived in closed form, namely the HeunT function, and Frobenius series solutions for the slit and the tube flows

This research investigated the effects of vibration on the rheological properties of dental composites and the adaptation of tooth cavity-composite interfaces. A portable vibratory packing device and two composites, micro-hybrid dental composite (MC) and nano-hybrid dental composite (NC), were evaluated. The frequency and amplitude of the vibratory packing device were measured. Dynamic oscillatory

Through two paintings by the Surrealistic artist Dali, the common tracks of subconscious expressionism in humans and the physics of the indescribable cosmos were sought by drawing an analogy between his paintings and rheology. A hitherto unexplored subject, yet astounding similarities could be found in his two masterpieces from the rheological point of view. Dalí’s subconscious development was in keeping

The present study investigates the combined effects of non-Newtonian rheology and unsteady nature of the fluid on dispersion of a soluble substance between two coaxial cylinders having wall permeability at the outer wall with the flowing fluid is modelled as Casson fluid. Generalized dispersion method in combination with a finite difference scheme is used to study the dispersion phenomenon. Using the

Exact solutions for shear stress in a polymeric liquid subjected to large-amplitude oscillatory shear flow (LAOS) contain many Bessel functions. For the simplest of these, for instance, the corotational Maxwell fluid, in the closed form for its exact solution, Bessel functions appear 42 times, each of which is inside a summation. Approximate analytical solutions for shear stress in LAOS often take

Aqueous foams are dispersions of gas bubbles in water, stabilized by surfactant, and sometimes particles. This multiphasic composition gives rise to complex rheological behavior under deformation. Understanding this behavior is important in many applications. Foam shows nonlinear rheological behavior at high deformation, which can be investigated by the large amplitude oscillatory shear (LAOS) experiments

In this study, we investigated the injection molding (IM) process for the production polymeric parts with thin walls. The injection molding process was numerically modelled, and thin-walled polymeric parts were injection-molded experimentally. In the case of polymeric parts with thin walls, it is critical to understand flow and heat transfer behavior in the mold during the process. Injection-compression

From the lattice Boltzmann equation, it is possible to derive the continuity equation and Cauchy’s equations of motion for a compressible medium, when one uses the Bhatnagar-Gross-Krook (BGK) - Welander approximation. From this, one can obtain the equations relevant to incompressible fluids. However, these require that the pressure be proportional to the density and the viscosity be dependent on the

It is of great importance to understand and predict Residence Time Distribution (RTD) during a singlescrew extrusion process for extruder design and operation optimization purposes. RTD depends on the extruder geometry, operating conditions, and material properties of non-Newtonian fluids. This paper presents the proper dimensionless parameters and RTD for the three-dimensional circulatory flow. These