Newtonian Fluid Research Articles

Film lifting and drainage of third-grade fluid on a vertical belt with surface tension

Understanding the film lifting and draining of fluid on a vertical belt with surface tension is crucial for improving predictive models in coating and lubrication processes. This paper presents a theoretical study on the film lifting and drainage of a third-grade fluid with surface tension. The driving mechanisms on a vertical belt are the belt’s upward movement, the gradient of surface tension, and gravity. The formulated nonlinear ordinary differential equation (ODE) is solved for a series-form solution using the Adomian decomposition method. Numerical computations are used to determine the stationary point placements and the thickness of the uniform film. The study elucidated that lift velocity shows a decreasing trend, while drainage velocity exhibits an increasing trend with increasing values of inverse capillary number C and Stokes number [Formula: see text]. The lift velocity shows an increase, whereas the drainage velocity demonstrates a decrease with an increase in the Deborah number De. With increasing values of [Formula: see text] and C, the stationary points shift away from the fluid–air interface, while an increase in De causes them to move towards the interface. Surface tension plays a role in supporting drainage and leads to a shift in the stationary points towards the belt. Newtonian and third-grade fluids are also compared in terms of velocity, stationary points, uniform film, and surface tension, providing insight into their behavior.

The Effect of Throughflow and Gravitational Modulation on Weakly Nonlinear Bio-Thermal Convection in a Porous Medium Layer

We investigate the impact of periodically varying gravitational fields and a throughflow on the bio-thermal Darcy–Brinkman convection within a porous medium layer saturated with a Newtonian fluid containing gyrotactic microorganisms. The study includes an examination of two types of a throughflow: one directed against the gravity field and another one along it. We assume that the gravitational modulation has a small amplitude, quantified as a second-order smallness in the dimensionless parameter ϵ, which represents the supercritical parameter of the Rayleigh number. For weakly nonlinear convection, a Ginzburg–Landau (GL) equation with a periodic coefficient is derived in the third order in ϵ. To analyze the heat and mass transfer, we numerically solve the GL equation. The numerical results reveal that the vertical throughflow in the bio-thermal convection exhibits a dual nature, allowing for both augmentation and a reduction of the heat and mass transfers. We investigate the influence of variations in the Vadasz number, Peclet number, bioconvective Peclet number, frequency, and amplitude of modulation on the heat and mass transfer. The effects of these parameters are depicted graphically, illustrating that higher values of the Vadasz and Peclet numbers, as well as increased modulation amplitude, positively impact the heat and mass transfer. In addition, a comparative analysis of modulated and non-modulated systems shows a significant effect of the modulation on the stability of systems.

Sedimentation of spheroids in Newtonian fluids with spatially varying viscosity

This paper examines the rigid body motion of a spheroid sedimenting in a Newtonian fluid with a spatially varying viscosity field. The fluid is at zero Reynolds number, and the viscosity varies linearly in space in an arbitrary direction with respect to the external force. First, we obtain the correction to the spheroid's rigid body motion in the limit of small viscosity gradients, using a perturbation expansion combined with the reciprocal theorem. Next, we determine the general form of the particle's mobility tensor relating its rigid body motion to an external force and torque. The viscosity gradient does not alter the force/translation and torque/rotation relationships, but introduces new force/rotation and torque/translation couplings that are determined for a wide range of particle aspect ratios. Finally, we discuss results for the spheroid's rotation and centre-of-mass trajectory during sedimentation. A steady orientation arises at long time whose value depends on the viscosity gradient direction and particle shape. These results are significantly different than when no viscosity gradient is present, where the particle stays at its initial orientation for all times. We summarize the observations for prolate and oblate spheroids for different viscosity gradient directions and provide plots for the orientation and centre-of-mass trajectory versus time. We also provide guidelines to extend the analysis when the viscosity gradient exhibits a more complicated spatial behaviour.

Numerical simulation and experimental study of hole cleaning

Insufficient hole cleaning causes tool wear and reduces drilling efficiency. Existing evaluation methods and models are limited. In this study, a universal method is proposed to assess hole cleaning efficiency (HCE). A coupled computational fluid dynamics and discrete element method (CFD-DEM) numerical model for non-Newtonian fluid simulation of cuttings transport is developed. The influence of various factors on HCE was analyzed from an energy and particle collision perspective, with a particular focus on the mechanisms of fluid viscosity and rate of penetration (ROP) on cuttings settling. Results show that increased fluid viscosity improves HCE, while excessive viscosity negatively affects it. Higher ROP results in increased solid particle concentration and collision probability, leading to energy loss and reduced efficiency. Lower HCE was observed when the inclination deviated from the vertical. The HCE can be significantly improved by increasing the fluid velocity and reducing the eccentricity. A comprehensive prediction model for HCE is established using Design of Experiment (DOE), dimensional analysis, and nonlinear regression. This model incorporates a generalized fluid apparent viscosity, taking into account the impact of each rheological parameter. Additionally, it can be applied to predict hole cleanliness in both Newtonian and non-Newtonian fluids. By comparing the experimental results of hole cleanliness in three distinct fluids, the regression model yielded reliable predictive results. The findings enhance understanding regarding how fluid properties and the ROP affect cuttings transport and enable precise and convenient prediction and optimization of hole cleaning efficiency.

Flow Modeling of a Non-Newtonian Viscous Fluid in Elastic-Wall Microchannels

The use of polymer microspheres is becoming increasingly widespread. Along with their most common applications, they are beginning to be used in the synthesis of photonic crystals, microstructure analysis and multiplexed diagnostics for disease control purposes. This paper presents a simple mathematical model that allows us to study the transport mechanisms involved in the deformation of an elastic microchannel under the flow stream of a power-law fluid. In particular, we analyze the momentum transfer to a non-Newtonian fluid (Polydimethylsiloxane, PDMS) due to the deformation of the elastic ceiling of a rectangular microchannel. Hooke’s law is used to represent the stress–deformation relationship of the PDMS channel ceiling. Stop-flow lithography is modeled, and the pressure exerted by the deformed PDMS ceiling on the fluid when the microchannel returns to its original form is taken into account. It is found that the response time of the elastic ceiling deformation increases with the channel width and length and decreases with the channel height independently of the power-law exponent of the injected fluid. However, an increase in the power-law exponent beyond unity causes an increase in the wall-deformation response time and the maximum deformation of the channel height compared to a Newtonian fluid.

Free falling of nonspherical particles in Newtonian fluids, B: Acceleration

The acceleration length of nonspherical particles is required for various aspects of system design. However, no simple or usable equations can be found in literature. Therefore, this study is designed to show that the force balance developed earlier for spherical particles, including the new exponential function for the history force, is also valid for nonspherical particles. To achieve this, a new history force parameter definition considering sphericity has been developed based on numerous experiments. The experimental results confirm the definitions of particle acceleration and velocity of nonspherical particles. The acceleration length can be described as a function of the Archimedes number, density ratio, and particle diameter by analogy to spherical particles, considering the terminal Reynolds number, drag coefficient, and history force parameter as functions of the sphericity. In most cases, the acceleration length describes the experiments well, but it is less accurate for cases of orientation change during acceleration.

Design and analysis of a novel magnetic helical swimmer

Magnetic helical swimmers are one type of robots that swim at low Reynolds number environments by rotating around the helix axis. Considering the importance and dramatic increase in the use of robots and microrobots in the near future, optimizing and increasing their efficiency is very important and noteworthy. Propulsion force and translational velocity are among the most important features of the magnetic helical swimmer, which improves the function of the swimmer as each of them increases. In this paper, a new design has been proposed for the magnetic helical swimmer by changing the geometry of the tail region, which has increased the propulsion force and improved its translational velocity. A suitable experimental setup has been designed and built in accordance with the required experiments to evaluate the translational velocity of the proposed swimmer. Using the experimental results, two models have been presented to express the translational velocity and propulsion force of the swimmer in terms of its angular velocity. The results of the experiments show that the propulsion force of the built swimmer is 698.89 % higher than that of the common magnetic helical swimmer with similar dimensions and the same environmental conditions in Newtonian fluid. At the end of the experiments, the motion of the proposed swimmer is simulated in the COMSOL software, and the results of the experiments are used to validate the simulation results. Finally, the effect of parameters such as the helix pitch and the number of turns of the helix on the translational velocity of the swimmer is investigated using the computer simulations.

On fluid-saturated poro-hyperelastic rotating cylinder: A centrifugal filtration

One of the applications of porous materials is centrifugal filtration. This study develops the Lagrangian equations that govern a steady-state, fluid-saturated, poro-hyperelastic, axisymmetric rotating cylinder. The formulation assumes incompressible solid and Newtonian fluid constituents to address the filtration process. The differential scheme takes into account the impact of porosity on the reduction of the drained shear and bulk moduli of the solid skeleton. Additionally, the normalized Kozeny-Carman formula considers the effect of porosity changes due to deformation on permeability. The Standard Galerkin Finite Element Method solves the derived equations using FlexPDE. ANSYS is unable to solve the current problem due to the lack of centrifugal and Coriolis accelerations in Darcy's law and its inability to account for changes in initial permeability and porosity resulting from the deformation of the solid skeleton. Therefore, the validation of the governing equations and the applied solution is investigated in three limited cases.It is shown that a rise in the angular velocity causes the expansion in the Von-Mises stress of solid constituent, radial displacement, negative pore pressure, and radial filtration velocity because of the increase in the centrifugal force. Also, the permeability and radial displacement grow with the initial porosity rise. The radial filtration velocity rises with the increased permeability resulting from the deformation. Moreover, drained shear and bulk moduli of the solid skeleton fall with increased porosity, resulting in a rise in the radial displacement. Besides, the radial displacement and filtration velocity expand with the increase of solid and fluid densities.

Compact Viscosity Sensors for Downhole Enhanced Oil Recovery Polymer Fluid Degradation Monitoring

Summary There are currently no technologies available to measure polymer solution viscosities at realistic downhole conditions in a well during enhanced oil recovery (EOR). In this paper, custom-made probes using quartz tuning fork (QTF) resonators are demonstrated for measurements of viscosity of polymer fluids in the laboratory. The electromechanical response of the resonators was calibrated in simple Newtonian fluids and in non-Newtonian polymer fluids at different concentrations. The responses were then used to measure field-collected samples of polymer injection fluids. In the polymer fluids, the measured viscosity values by tuning forks were lower than those measured by the conventional rheometer at 6.8 s−1, closer to the solvent viscosity values. However, the predicted rheometer viscosity vs. QTF-measured viscosity showed a distinct exponential correlation (R2=0.9997), allowing for an empirical calibration between the two viscometers for fluids having the same solvent and polymer compositions. The QTF sensors produced acceptable viscosity measurements of polymer fluids within the required polymer concentration ranges used in the field and predicted field sample viscosities with less than 1–2 cp (or 10–20%) error from the rheometer data. Results were validated based on separate independent tests where the devices were used to measure the viscosity of Newtonian fluids and non-Newtonian polymer fluids in a series of consecutive dip tests, simulating more realistic usage. These devices can be used to measure either the “relative” viscosity changes from a polymer solution prior and post-injection or to measure a “calibrated” viscosity via empirical exponential correlation. The compact QTF sensors developed in this study can be easily integrated into portable systems for laboratory or wellsite deployment as well as logging tools for downhole deployment. This work also demonstrates the ability of these QTF devices to make sensitive viscosity measurements at high-frequencies, opening opportunities for their use in high-frequency rheology studies of EOR fluids.

Endothermic and exothermic chemical reactions’ influences on a nanofluid flow across a permeable microchannel with a porous medium

The compact dimensions and large surface area-to-volume ratio characteristic of microchannel geometries can efficiently utilise endothermic and exothermic chemical reactions to enhance heat transfer, control temperature, adjust reactivity, intensify processes and develop innovative thermal management techniques. Becasue of this, the exothermic and endothermic chemical reaction mechanism is explored by considering the titanium oxide (TiO2) nanoparticles with water (H2O) as the base fluid. An incompressible Newtonian fluid flows through the porous microchannel. The pressure gradient factor assumes the flow in the microchannel. Energy and solutal transportation analyses are made with Robin’s boundary conditions and activated energy phenomena. Similar variables are introduced to convert the model into non-dimensional. A numerical scheme, namely the Runge–Kutta-Fehlberg 45th (RKF-45) scheme, is implemented to execute solutions. The results explore that thermal distribution decreases for elevated activation energy values and Biot number values in the exothermic case while enhanced in the endothermic case. The rate of thermal distribution declines with the addition of solid fractions and chemical reaction parameters in the endothermic case; the opposite trend is observed in the exothermic case.

Convective instability of Ekman boundary layer flow of a Newtonian fluid over a stretchable rotating disk

ABSTRACT This paper examines a linear convective instability of an incompressible, Newtonian, viscous fluid rotating over a stretchy spinning disk in an Ekman boundary layer flow. First time in the literature, a numerical analysis of impacts of the stretching mechanism on the stability of the Ekman flow in the presence of the Coriolis force has been carried out, where the bottom disk is allowed to uniformly extend in radial direction. The von Kármán similarity transformations have been used to convert the governing equations of motion into a system of non-linear coupled ordinary differential equations (ODEs) in non-dimensional variables. Then velocity profiles of the flow have been obtained by numerically solving these dimensionless ODEs. The neutral stability curves were then obtained by performing a linear stability analysis for the convective mechanism by using the Chebyshev collocation method. Surface stretching has a globally stabilizing influence on both Type-I and Type-II instability modes of the Ekman flow, according to the stability curves. Then, the result established from the stability curves has been verified by calculating total kinetic energy change due to induced perturbations in the flow system. y.

Analysis of quasi-variational–hemivariational inequalities with applications to Bingham-type fluids

In this paper we study the sensitivity analysis of elliptic quasi-variational–hemivariational inequalities with constraint. The upper semicontinuity property of the solution map with respect to a parameter is established. An application to the steady-state incompressible Navier–Stokes equation with mixed boundary conditions in a model for a generalized Newtonian fluid of Bingham-type is provided. The boundary conditions represent a generalization of the no leak condition, and a multivalued and nonmonotone version of a nonlinear Navier–Fujita frictional slip condition. Furthermore, a sensitivity result is proved for the weak formulation of the model when all the data are subjected to perturbations. Finally, for the Bingham-type fluids, an optimal control problem is studied.

Laminar mixing of Newtonian and non‐Newtonian fluids in SMX static mixer

AbstractThis report is focused on understanding the mixing performance of Newtonian and non‐Newtonian fluids in an SMX static mixer through computational fluid dynamics (CFD) study in Simcenter STAR‐CCM+. For this, the standard SMX mixer with four mixer elements of radius 26 mm was chosen. The aspect ratio (L/D) was taken as 1. The model constructed was compared using pressure drop ratio values available in literature. First, the design was validated for Newtonian fluid, then for shear‐thinning fluid (non‐Newtonian). Mixing patterns produced through particle tracking approach revealed how blending improved as the fluid moved downstream and interacted with increasing number of mixer elements. A sensitivity study was undertaken to investigate the effect of particle injection mechanism on the mixing process. Two injection methods, vertical and horizontal, were explored to check the influence of injection position on mixing. The results indicate that for the given configuration irrespective of the injection location, at least four mixing elements are needed to achieve good mixing for both Newtonian and shear‐thinning fluids investigated in this study. Statistical reports were used to quantify mixing to understand the mixing behaviour for Newtonian and non‐Newtonian fluids with change in Reynolds number. At high Reynolds number, non‐Newtonian fluids exhibited better mixing abilities. Further, efforts were taken to optimize the various design parameters to produce the most optimum solution with a single mixer element for Newtonian fluid.

Start-Up Rotation of a Porous Colloidal Sphere in a Cavity

The starting rotation of a porous sphere induced by the sudden application of a continuous torque about its diameter at the center of a spherical cavity filled with an incompressible Newtonian fluid at low Reynolds numbers is analyzed. The unsteady Stokes and Brinkman equations governing the fluid velocities outside and inside the porous particle, respectively, are solved via the Laplace transform, and an explicit formula of its dynamic angular velocity as a function of the pertinent parameters is obtained. The behavior of the start-up rotation of an isolated porous particle and the cavity wall effect on the particle rotation are interesting. The angular velocity of the particle grows incessantly over time from an initial zero to its final value, while the angular acceleration declines with time continuously. In general, the transient angular velocity is an increasing function of the porosity of the particle. A porous sphere with higher fluid permeability rotates at higher angular velocity and acceleration relative to the reference particle at any elapsed time but lags behind the reference particle in the percentage growth of angular velocity towards the respective terminal values. The transient angular velocity decreases with increasing particle-to-cavity radius ratio, but it is not a sensitive function of the radius ratio when the resistance to fluid flow inside the porous particle or the radius ratio itself is small.

Physical Properties of Paste Synthesized from Wet- and Dry-Processed Silver Powders.

This study compares the characteristics and low-temperature curing properties of pastes prepared from silver (Ag) powders synthesized by either wet powder (WP) or dry powder (DP) processing. The WP synthesis of electrode particles has the advantage of controlling the average particle size and particle size distribution but the disadvantage of producing low-purity, crystalline particles because they are synthesized through chemical reduction at less than 100 °C. Conversely, the DP synthesis of electrode particles has the advantage of producing pure, highly crystalline particles (due to synthesis at high temperatures) but the disadvantage of a high processing cost. WP and DP were used to manufacture pastes for low-temperature curing, and the physical properties of the pastes and the electrode characteristics after low-temperature curing were compared between powder types. Shear stress as a function of the shear rate shows that the WP paste is a plastic fluid, whereas the DP paste is a pseudoplastic fluid, closer to a Newtonian fluid. Screen printing the Ag pastes and curing for 30 min at 130 °C produces a nonconductive WP paste, whereas it produces a DP paste with a conductivity of 61 mΩ/sq, indicating that the highly crystalline DP paste is advantageous for low-temperature curing.

An Experimental Study on the Effect of Nanofluids on the Thermal Conductivity and Rheological Properties of a Coolant for Liquids

Thermal conductivity and viscosity are important properties for nanofluids as they significantly affect the flow and heat transfer process. To date, the rheological properties of water-based nanofluids have been well studied, while the results are scarce for non-aqueous nanofluids. In this study, the thermal conductivity and rheological properties of two different kinds of oxide nanofluids (CuO and Al2O3) in a typical commercial data center focusing on liquid coolants were systematically investigated at different mass fractions and temperatures. The results showed that the addition of nanoparticles can significantly improve the heat conduction capacity of mineral oil coolants. There is an average increase in thermal conductivity of up to 20–25%. The shear rate–shear stress and shear rate–viscosity curves all showed that mineral oil coolant-based oxide nanofluids behaved as Newtonian fluids and that nanoparticles did not cause the increment in viscosity. The effect of temperature on rheological properties was also studied, and the result showed that high temperatures resulted in low viscosity and shear stress. Finally, the effect of particle type was investigated, and it was found that no matter what kind of nanoparticles were added, their effects on the rheological behaviors were the same.

Dynamics of a single bubble in Newtonian and non-Newtonian fluids: Experimental and simulation approaches

The intricate nature of non-Newtonian fluid rheology has raised notable attention, particularly in gas–liquid systems, where the dispersed bubbles may generate shear forces and change the shear-dependent viscosity of the surrounding liquid. While the effective shear rate, γ̇eff=vb/Db, is commonly used to approximate the shear-thinning viscosity around spherical bubbles, deviations may arise for deformed bubbles present in real systems. This work combines laboratory experiments and numerical simulations to investigate the evolution of a single rising bubble in three different systems: water, glycerol/water solutions characterizing viscous-Newtonian systems, and carboxymethyl cellulose (CMC) aqueous solutions exhibiting shear-thinning. The experiment was performed with bubble sizes of 1–9mm using imaging techniques. The measured fluid rheology is modeled by the Carreau model, and used in 3D direct numerical simulations based on a diffuse interface approach. The shear-thinning behaviors are found to increase the bubble terminal velocity through two distinct mechanisms: reducing the apparent viscosity around the bubble and promoting the bubble deformation. The extent of the shear-thinning effect depends on the three dominating regimes under which different rheology parameters play a significant role. Finally, empirical models for bubble terminal velocity and drag coefficient are evaluated using two shear-thinning viscosity estimations, based on the effective shear rate and the average shear-thinning viscosity near the bubble interface. The good agreement between experimental and simulation results validates the proposed models.

Modeling and analysis of hybrid-blood nanofluid flow in stenotic artery

Current communication deals with the flow impact of blood inside cosine shape stenotic artery. The under consideration blood flow is treated as Newtonian fluid and flow is assumed to be two dimensional. The governing equation are modelled and solved by adopting similarity transformation under the stenosis assumptions. The important quantities like Prandtl number, flow parameter, blood flow rate and skin friction are attained to analyze the blood flow phenomena in stenosis. The variations of different parameters have been shown graphically. It is of interest to note that velocity increases due to change in flow parameter gamma and temperature of blood decreases by increasing nanoparticles volume fraction and Prandtl number. In the area of medicine, the most interesting nanotechnology approach is the nanoparticles applications in chemotherapy. This study provides further motivation to include more convincing consequences in the present model to represent the blood rheology.

Simulation of vortices and numerical evaluation of heat transfer using multiwalled carbon nanotubes-based hybrid nanofluid for viscous flow sensor

ABSTRACT In this paper, we aim at the simulation of setup for vortex generation and measurement. This project will lead to designing the experimental setup to create vortices and development of heat flow sensors. The working fluid for the vortex generator is hybrid nanofluid such as Iron (III) Oxide-MWCNT and propanol. The usage of these hybrid fluids was considered due to their better physical and chemical properties compared to water and other conventional fluids. Ansys Fluent was used to simulate the experiment. Viscosity of the fluid increases for both hybrid nanofluids, from inlet to outlet by a magnitude of 10 times (for Fe3O4 + MWCNT: 5.3 × 10−5 Pa.s to 6.3 × 10−4 Pa.s; for Al2O3 + MWCNT: 7.5 × 10−5 Pa.s to 6.5 × 10−4 Pa.s), for laminar flow (Reynolds number = 400). Vortex generation increases the viscosity of the hybrid mixture but not water (for water, it stays constant across the channel at 4.9 × 10−4 Pa.s). Vortex induced viscosity is seen in hybrid mixtures. Strain thinning due to vortex formation is not observed, therefore the behavior of the mixtures is along the lines of Newtonian fluids.

Simulation of expansion and contraction for sudden plastic flow of Bingham cement grout and Newtonian fluids in a rectangular duct, using the lattice Boltzmann method

Bingham-type fluids are crucial in many industries and in geology. This study examines their behavior in reinforcing fractured rocks. Rheological properties were derived from experimental data of a water-cement mixture. Computational simulations were conducted using Lattice Boltzmann Method, with a modification to the relaxation parameter. Behavior of these mixtures in narrow ducts that widen and narrow suddenly, common in fractured rocks, was analyzed. Comparing Bingham and Newtonian fluids in various duct shapes provided insight into pressure distribution. Findings demonstrate that both cement-water mixtures, with or without addition of cement, adhere to Forchheimer flow patterns. Furthermore, it is observed that Newtonian fluids generate more intense vortices in expansive and contractive areas, resulting in higher pressure drops compared to Bingham plastics. The ultimate goal is to propose a predictive model based on mortar reinforcement for fractured rocks, taking into account rheological properties and water-cement ratio, thus reducing the need for costly experiments.