Plastic Fluid Research Articles

Effect of aspect ratio of enclosure on free convection from horizontal cylinders in Bingham plastic fluids

Effect of aspect ratio of enclosure on free convection from horizontal cylinders in Bingham plastic fluids

Numerical study on the flow of Bingham plastic fluids around an array of cylinders

Numerical study on the flow of Bingham plastic fluids around an array of cylinders

Chromatographic methods for the determination of free bisphenol A in technical and food products

The article provides a brief overview of chromatographic methods for the determination of free bisphenol A in technical and food products. Bisphenol A (BPA) is used as a monomer in the production of some plastics and epoxy resins. Free BPA may be present in quantities exceeding acceptable levels in plastic food containers and in food products packaged in these containers. Maximum permissible concentration (MPC) of BPA in the air of the working area is 5 mg/m3, which in terms of liquid is 5 µg/dm3. Maximum permissible concentration for the content of BPA in water, in water bodies for domestic, drinking and community water use is 0.1 mg/dm3. In European countries for plastics in contact with food, the BPA migration value is 0.6 mg/kg. Despite the relatively low toxicity of BPA, it can accumulate in the human body and cause harmful effects. To determine BPA in plastic, food products, and biological fluids, gas chromatography with preliminary derivatization by silylation or acylation of the analyte is most often used. Gas chromatographic techniques for direct chromatography on heat-resistant columns have also been developed. A fluorometric detector and a mass spectrometric detector are used as detection devices, along with a flame ionization detector. An alternative method for determination of BPA is HPLC with optical and mass spectrometric detection methods. The TLC method was also developed for the determination of BPA. For the preparation of BPA samples, solid-phase extraction (SPE), liquid-liquid extraction (LLE), dispersive liquid-liquid microextraction (DLLME), combined extraction method with acetonitrile separation (QuEChERS) are used.

Leaching of triphenyl phosphate and tri-n-butyl phosphate from polystyrene microplastics: influence of plastic properties and simulated digestive fluids.

Microplastics have gained considerable attention as a growing environmental problem owing to their potential to serve as vectors for harmful chemicals. However, the leaching of these chemicals from microplastics is unclear. In this study, we investigated the leaching of two organophosphate flame retardants, triphenyl phosphate and tri-n-butyl phosphate, from polystyrene microplastics in simulated digestive fluids and water, and polypropylene microplastics were simultaneously used for comparison with polystyrene microplastics. The results indicated that the first-order kinetic model best explained the leaching process, suggesting that leaching was related to the release of organophosphate flame retardant molecules at the polymer surface. Additionally, the size and crystalline state of the microplastics had a significant effect on the leaching, whereas organophosphate flame retardant content had a minimal impact. Simulated digestive fluids facilitated the leaching to a different extent, and under these influencing conditions, leaching percentages from polystyrene microplastics did not exceed 0.51%. Therefore, leaching from PS microplastics may not be an important source of OPFRs in the environment. However, the release of organophosphate flame retardants can be considerably enhanced with the breakdown of polystyrene microplastics to polystyrene nanoplastics.

Optimization of hydraulically amplified electrostatic actuators based on an evolutionary strategy and finite element model to match the performance of the human triceps surae muscle fibres

Artificial muscles are required to improve prosthetics, exoskeletons and other industrial robotics applications. Compared to other technologies like pneumatic actuators and shape memory alloys, Peano hydraulically amplified self-healing electrostatic (HASEL) actuators have the most similar stress output, work density and specific energy as biological muscle. This work designs an artificial muscle fibre that simulates human triceps surae muscle fibre using Peano-HASEL actuators. Analytical models are derived to calculate the capacitance and efficiency of the actuator. A three-stage methodology of an evolutionary strategy, finite element (FE) model and a severity analysis is proposed to optimize the geometrical parameters of the artificial muscle fibre, evaluate its performance, and identify potential risks. The finite element model created in this work produces a full multi-physics simulation coupling the electro-mechanical and fluid–solid interactions, which fits any liquid dielectric volume and for the first time simulates an entire activation cycle. The finite element model further simulates the force-length and force-velocity relationships not seen in previous work and facilitates understanding of the dynamics of the Peano-HASEL actuator, including damping characteristics. Plastic deformation and fluid pocket phenomenon due to materials are found during the simulation, which could give new insights for the analysis of electrical breakdown and mechanical stress failure. The three-stage design methodology described in this paper suggested that an artificial muscle with 80 mm width, 0.4 radian initial central angle, 20 um film thickness and 7.6 kV activation voltage would best match the human triceps surae muscle behaviour. The designed artificial muscle fibre can produce 80% of peak maximum strain (∼18.8%), have an efficiency of 22%, generate high loads within 5% strain and restore muscle-like performance beyond 5% strain.

Lubrication of asymmetric rollers considering viscosity as function of mean temperature

A theoretical analysis of an asymmetric roller bearing system with cavitation that is hydro-dynamically lightly loaded and lubricated by a thin, incompressible fluid is presented. The lubricant adheres to the non-Newtonian Bingham plastic fluid concept, in which the viscosity of the fluid should change depending on the mean film temperature. The continuity and momentum equations, which regulate fluid flow, are first solved analytically and then numerically using MATLAB. Through graphs and tables, some key bearing features are addressed and further explained. This leads to the conclusion that there is a discernible difference between Newtonian and non-Newtonian fluids in terms of pressure, temperature, load, and traction. The findings are good in line with the body of literature.

Development of glow-in-the-dark and color-tunable poly(methyl methacrylate) plastic concrete immobilized with rare-earth aluminate

A simple method is reported for the prospective industrial production of lightweight poly(methyl methacrylate) (PMMA) plastic concrete with persistent afterglow. Nanoparticles (NPs) of lanthanide activated aluminate (LAA) pigment were molded into a plastic bar. With the uniform dispersion of LAA NPs in the plastic fluid, the produced plastic bar can be made transparent. was A simple polymerization of methyl methacrylate (MMA; bulk material) blended with silica nanoparticles (filler), and LAA nanoparticles (luminous agent) was applied in the presence of 2,2-azobisisobutyronitrile (AIBN) catalyst to provide photoluminescent PMMA plastic concrete. In studies, LAA NPs were found to have sizes between 9 and 95 nm. When excited at 369 nm, the luminescent PMMA concrete displayed an emission peak at 518 nm. For pigment concentrations over 1%, persistent photoluminescence was observed, whereas fluorescence was tracked for the LAA contents equal to or below 1%. The manufactured plastic concrete was shown to exhibit photochromism from colorless under daytime light to green below UV, and greenish-yellow in the dark. By measuring the static contact angle, we were able to confirm the excellent superhydrophobic activity. Indications of enhanced UV protection and photostability were monitored upon increasing LAA ratio in the concrete bulk. Strong durability, reversibility and continuous afterglow emission were hallmarks of the photoluminescent hard composite concrete. The created plastic concrete morphology, elemental content and hardness properties were studied.

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.

Development of Heavy-Weight Hematite-Based Geopolymers for Oil and Gas Well Cementing.

In the petroleum industry, ordinary Portland cement (OPC) is utilized for different cementing applications. Yet, there are some technical and environmental issues for the usage of OPC in well cementing. The technical problems include gas invasion while setting, instability at corrosive environments, cement failure while perforation and fracturing due to high stiffness and brittleness, and strength reduction and thermal instability at elevated temperatures. Moreover, OPC production consumes massive energy and generates high greenhouse gas emissions. This study introduced the first hematite-based class F fly ash geopolymer formulation that can be used in oil and gas well cementing. Different properties of the designed slurry and hardened samples such as rheology, thickening time, strength, and elastic and petrophysical properties were evaluated. Moreover, mixability and pumpability challenges of heavy-weight geopolymer slurries were investigated. Unlike most of the studies in the literature, this work used 4 M NaOH solution only as an activator that can reduce the overall cost. The results showed that increasing the hematite percentage significantly decreased the thickening time. The developed formulation fell within the recommended fluid loss ranges for some cementing applications without using a fluid loss control additive. A proposed mixture of retarder and superplasticizer was introduced to enhance the thickening time by almost 5 times. The compressive strength increased by 49% and the tensile strength was enhanced by 27.4% by increasing the curing time from 1 to 7 days. The improvement in both compressive and tensile strength with curing time indicated that the geopolymerization reaction continued for extended time but with a smaller rate. The developed slurry acted more like a power law fluid at low temperatures and more like a Bingham plastic fluid at high temperatures. The elastic properties of the developed geopolymer samples proved that they are more flexible than some cement systems.

Core Variation of a Non-Newtonian Fluid in an Annular Cylinder

The objective of the paper is to investigate the variation of core thickness of a non-Newtonian fluid in an annular cylinder at the entrance region. It is derived numerically, with no prior assumptions on the form of the Velocity profile. The thickness of the core is examined at each cross section of annuli for various values of Bingham number and aspect ratio by applying mass balance equation. The effect of various parameters on the flow rate are obtained graphically. The examination incorporates Bingham plastic fluids, Casson and Herschel-Bulkley fluid. The administering equations are solved using an iterative procedure by converting non-linear algebraic equation, expressing the variation in pressure in terms of core thickness obtained using the mass balance equation and plug core velocities along the boundary layers. The core thickness is obtained numerically by solving this equation using an iterative procedure. MATLAB programming tool has been employed to get the graphical variation of core thickness for different values of aspect ratio. The comparisons have been made between the obtained results and the results of Casson and Herschel-Bulkley fluids. Also, we find excellent agreement between our numerical results and the results available in literature.

Calculating the entropy generation of a Bingham plastic fluid flow due to a heated rotating disk

We present the numerical study of the flow on a heated rotating disk for Bingham plastic fluid. Thermo-physical properties and viscous dissipation are assumed with the influence of entropy generation. This kind of study has a significant attentiveness in the fields of applied engineering for their increased mathematical advantages. We analyzed the solutions of fluid flow and entropy phenomenon for the Bingham fluid. The similarity solution was firstly presented by von Kármán for Newtonian fluid, it is found to be beneficial for the Bingham plastic fluid by transforming the boundary layer partial differential equations into ordinary differential equations. Shooting method is used to crack the dimensionless ordinary differential equations. The Bingham model is momentous for unlimited high shear rates for this we suggest these numerical data provide accurate description of the Bingham fluid and entropy minimization near a rotating disk. The outcomes exhibits that the azimuthal velocity profiles upsurges for upward values of Bingham fluid, and the similar behavior for tangential radial velocity is perceived. The temperature curve is noted to be enhanced for higher magnitudes of Eckert number and thermal conduction parameter. The soret number and diffusivity coefficient creates increment in concentration curve. The entropy function in the flow system enhances for up surging the inputs of Bingham fluid coefficient and thermophoresis diffusion. The results are locally similar for various parameters. We have also included the comparison analysis with published works.

Analysis of biological mechanism of blood flow containing nanoparticles through an arterial stenosis

ABSTRACT This article aims to discuss the flow of nanoparticles in the blood through a stenosed artery in the presence of a magnetic field and periodic body acceleration. The overlapping shape of stenosis is chosen to show the impact of blood flow. The Bingham plastic fluid model is utilized to capture the non-Newtonian behavior of blood in the stenosed artery under diseased conditions. The resultant equations are solved analytically using the regular perturbation method. The impact of various emerging parameters on velocity, flow rate, effective viscosity, and wall shear stress are presented through graphs and discussed in detail. It is noticed that liquid velocity and flow rate increase whereas effective viscosity decreases with an increase in slip velocity and Womersley’s frequency parameter. It is also noted that liquid velocity and flow rate are decreased by enhancing the Lorentz force. The increase in body acceleration enhances fluid velocity.

CFD-based investigation on the flow of Bingham plastic fluids through 90^circ bends

In this paper, CFD-based results are presented on the estimation of losses in bends with validated numerical models for single-phase, incompressible Bingham fluids. Five fittings were investigated: 90^circ bends of different R/D ratios between 1 and 10. Bingham plastic fluids were studied with Hedström numbers in the wide range from 1 to 10^9. Loss coefficients are given as the function of the generalized Reynolds number ({textrm{Re}_textrm{gen}}= 0.1–17 800) and the generalized Dean number ({textrm{De}_textrm{gen}}= 0.1–12 600). The paper presents friction factors as well that were consistent with the literature. It was shown that at low generalized Dean numbers of {textrm{De}_textrm{gen}}< 40, the losses of the bends were caused purely by the wall friction and can be estimated from the {textrm{De}_textrm{gen}}. In a broad range of higher {textrm{Re}_textrm{gen}} and {textrm{De}_textrm{gen}} numbers, the loss coefficients were separated at the basis of the Hedström numbers. This phenomenon was mainly observable in the case of high curvature and was attributed to the flow patterns. Our study investigated this range with the bend of R/D=1 in detail: flow patterns in the bend and at the upstream side of the fitting were examined. An approximating equation and the fitting parameters were also given for loss coefficients.

CFD-based Estimation of Friction Factor in Rough Pipes with Herschel-Bulkley Fluids

The appropriate estimation of frictional losses in a pipeline system is essential. So far, little attention has been paid to determining the friction factors with non-Newtonian fluids, especially in rough pipes. This study aims at calculating the friction factor using validated three-dimensional Computational Fluid Dynamics models in Ansys CFX. Steady-state computations are performed with three different incompressible Herschel-Bulkley fluids in rough pipes with relative roughness of the inner pipe surface ε = 0.0005 – 0.01. A power-law type bath gel as a test fluid is used for experiments to validate our numerical model. The numerical results are compared with the measured values and also with numerous existing friction factor estimation models with the help of generalization of the Reynolds number in the relevant engineering range of Regen = 100 – 40,000. This paper shows that the existing approximations can not accurately describe the friction factor with pseudoplastic fluids in rough pipes. On the contrary, in the case of Bingham plastic fluid, a new, explicit calculation relation is found in a unified form accepted by the literature.

Numerical study on the muck flow behavior in the screw conveyor during EPB shield tunneling

The muck flow behavior in the screw conveyor determines the pressure in the excavation chamber. The pressure in the chamber should be reduced to the atmospheric pressure at the outlet of the screw conveyor. Otherwise, the soil and water mixture would spew out form the screw conveyor, resulting in the pressure loss and face failure. In this study, three-dimensional numerical analyses of the muck transport performance of screw conveyor were performed using Computational Fluid Dynamics (CFD). The muck was assumed to behave as a Herschel-Bulkley (H-B) plastic fluid. A new model coupling rheological and wall slip models was developed and validated by a laboratory test. The error of the pressure transfer and the flow rate between simulation and test is around 3.8%. Through parametric analysis, the influence of the rheological parameters of muck and the working parameters of the screw conveyor on the muck flow behavior is further explored, and a spewing failure surface is given for the control of rheological parameters of the conditioned soil. The results in this study could provide some suggestions for soil conditioning and the optimization of screw conveyor performance.

Design of suspension culture system with bubble sparging for human induced pluripotent stem cells in a plastic fluid

Design of suspension culture system with bubble sparging for human induced pluripotent stem cells in a plastic fluid

Environmentally Friendly Additives for Aqueous Drilling Fluid Systems: Optimum Flow Characteristics and Models

Recently, renewable additives are incorporated to design novel drilling fluid formulations with properties meeting the needs of downhole atmospheres and environmental regulations. The work deals with the investigation, optimization, and modeling of the rheological properties of new aqueous drilling fluid systems incorporated with green sliver nanoparticles and mastic gum and the estimation and optimization of the flow mathematical models. The average range of the experimental values for apparent viscosity, plastic viscosity, yield point, and low-shear-rate yield point for the prepared drilling fluids are 22-38 cP, 8-24 cP, 26-32 lb/100ft2, 18-35 lb/100ft2 respectively, while the optimum values estimated by ANOVA are 38.79 cP, 25.12 cP, 33.47 lb/100ft2, and 42.16 lb/100ft2 respectively. The optimum rheological properties are achieved by incorporating 17.07 ml of mastic gum and 1.6 ml of silver NPs colloids. The outcomes showed that the green additives looked talented to be applied for governing drilling fluid characteristics within the oil industry-recommended standards. The results of modeling the flow of the optimized drilling fluid indicated that it is Pseudo plastic fluid that exhibited non-Newtonian behavior and shear thinning. The Bingham-plastic flow model was explored to be the topmost model that can describe the flow behavior of the optimized drilling fluid system.

Preparation of transparent photoluminescence plastic concrete integrated with lanthanide aluminate

A simple strategy was presented for potential industrial preparation of persistent afterglow lightweight plastic concrete toward smart hard surfaces. Rare-earth activated aluminate (REA) pigment nanoparticles (NPs) were integrated into plastic bar. The transparency of the prepared plastic bar can be achieved by consistent distribution of REA NPs in the plastic fluid. Unsaturated polyester resin (bulk material) was mixed with silica nanoparticles (filler) and REA NPs (luminescent agent) using methyl ethyl ketone peroxide as hardener. The curing process was accomplished for a few minutes at room temperature. The diameters of REA NPs were reported in the range of 6–11 nm. The phosphor-concrete composite can be industrially applied onto a variety of hard surfaces. The photoluminescent plastic concrete showed an emission band at 515 nm upon excitation at 372 nm. Persistent photoluminescence was detected for pigment concentrations higher than 1%, whereas fluorescence emission was monitored for pigment concentrations equal to 1%. Photochromism was observed for the prepared plastic concrete as different colors were detected under different light conditions, including colorless under daytime light, green underneath UV rays, and greenish-yellow under darkness as proved by luminescence spectra and CIE Lab parameters. The static contact angle measurements proved good superhydrophobic activity. An improved UV protection and photostability were detected. The photoluminescent hard composite concrete displayed highly durability and reversible persistent afterglow emission. The morphology, elemental composition and hardness features of the prepared plastic concrete were investigated.

Study of multilayer flow of a bi-viscous Bingham fluid sandwiched between hybrid nanofluid in a vertical slab with nonlinear Boussinesq approximation

Bi-viscosity Bingham plastic fluids are used to understand the rheological characteristics of pigment–oil suspensions, polymeric gels, emulsions, heavy oil, etc. In many industrial and engineering problems involving high-temperature situation, a linear density-temperature variation is inadequate to describe the convective heat transport. Therefore, the characteristics of the nonlinear convective flow of a bi-viscous Bingham fluid (BVBF) through three layers in a vertical slab are studied. The two outer layers of the oil-based hybrid nanofluid and the intermediate layer of BVBF are considered. The thermal buoyancy force is governed by the nonlinear Boussinesq approximation. Continuity of heat flux, velocity, shear stress, and temperature are imposed on the interfaces. The governing equations are derived from the Navier–Stokes equation, conservation of energy, and conservation of mass for three layers. The nonlinear multi-point (four-point) boundary value problem is solved using the differential transform method (DTM). Converging DTM solutions are obtained, and they are validated. The entropy equation and Bejan number were also derived and analyzed. It is established that the nonlinear density–temperature variation leads to a significant improvement in the magnitude of the velocity and temperature profiles due to the increased buoyancy force, and as a result, the drag force on the walls gets reduced. The drag force on the slab gets reduced by decreasing the volume fraction of nanoparticles. Furthermore, nonlinear convection and mixed convection give rise to an advanced rate of heat transport on the walls and thereby to an enhanced heat transport situation.

Effect of Engineered Roughness on the Performance of Journal Bearings Lubricated by Bingham Plastic Fluid Using Computational Fluid Dynamics (CFD)

A journal bearing is a machine element that is used to keep the shaft rotating about its axis. The increasing demand for journal bearing applications in high-speed machines that are efficient and economical has resulted in the need for improvements to the acoustic and tribological performance of journal bearings. In order to improve the tribological and acoustic performance, this study aims to propose a novel journal bearing design by introducing a roughness condition in a specific zone of the stationary bearing surface. In addition, the impact of the application of engineered roughness on the performance of Bingham-plastic-lubricated bearings is investigated in more detail. Considering the effect of cavitation, the analysis was conducted using a 3D computational fluid dynamics (CFD) model of a journal bearing. In comparison with the Reynolds equation—which is inertialess—for lubrication analysis, the use of a 3D CFD model based on Navier–Stokes equations reflects more detailed flow characteristics. Moreover, in this work, variations in the area of surface roughness were employed, resulting in various roughness patterns on the surface of the journal bearing, so that the acoustic and tribological performances of the journal bearing were anticipated to be enhanced. The findings of this study show that under non-Newtonian lubrication of the bearing, the engineered roughness has a strong effect in altering the tribological performance. Furthermore, the well-chosen roughened surface was proven to be more pronounced in enhancing the load support and reducing the friction force. The simulation results also show that using an engineered surface has little effect on the noise of the bearing.