Power Law Lubricants Research Articles

Coupled heat and mass transfer mathematical study for lubricated non-Newtonian nanomaterial conveying oblique stagnation point flow: A comparison of viscous and viscoelastic nanofluid model

Abstract The lubrication phenomenon plays a novel role in the chemical industries, manufacturing processes, extrusion systems, thermal engineering, petroleum industries, soil sciences, etc. Owing to such motivated applications, the aim of the current work is to predict the assessment of heat and mass transfer analysis for non-Newtonian nanomaterial impinging over a lubricated surface. The flow is subject to the oblique stagnation point framework. The lubricated phenomenon is observed due to viscoelastic nanofluid. The impacts of chemical reaction are also endorsed. The fundamental conservation laws are utilized to model the flow problem and similarity transformation are used to transform the governing system of partial differential equations into ordinary differential equations. A thin layer of power law lubricant is used to enhance the lubrication features. The numerical object assessment regarding the simulation process is captured by implementing the Keller Box scheme. The physical characterization endorsing the thermal fluctuation with flow parameters is inspected.

Heat transfer in Jeffrey fluid flow over a power law lubricated surface inspired by solar radiations and magnetic flux

For faster speeds and higher load operations, modern bearings use lubricants with polymer components of increasing molecular weight. These lubricants exhibit non-Newtonian rheological behaviour. For industrial lubrication and bearing applications, power-law lubricants are often used. This article is modeled through the slip as an interfacial condition to demonstrate the role of power-law lubrication on the stagnation point flow of magneto Jeffrey fluid. The significant features of magnetic flux over the lubricated surface are studied to control the flow and thermal mechanisms. The heating effect caused by the non-linear thermal radiations is analyzed. Interfacial conditions are developed by applying the continuity of fluid-lubricant shear-stress and velocity at the interface. The similarity transformation is used to acquire and then numerically solve the non-linear ordinary differential equations. By using MATLAB's bvp4c finite difference scheme, local similarity solutions are obtained for a power-law index equal to (1/2). The effects of lubrication, MHD, and thermal radiation on all the relevant parameters are scrutinized and illustrated in graphs. It is observed that the effect of slip and Jeffrey's material parameters raise the numerical value of the coefficient of skin friction along the x-axis. Further, the stronger magnetic field has the more tendency to reduce the fluid momentum and encourages the thermal field. Additionally, increasing the Prandtl number and Schmidt number raises the heat and mass transfer rates, respectively.

Numerical Simulation for Flow and Heat Transfer of a Nanofluid Over Lubricated Stretchable Surface

The lubricants mostly used in industry have non-Newtonian properties and adhere to a variety of constitutive connections. The power law lubricant, which follows the Ostwald model and is widely used in engineering lubrication, is one of them. In this study the flow analysis of nanofluid in the vicinity of a stagnation point over a lubricated stretching surface has been investigated. The lubrication is provided by a thin layer of variable thickness of power-law fluid. Impact of thermophoresis and Brownian motion is also investigated. To acquire the dimensionless governing equations utilized an appropriate transformation. A newly developed powerful numerical procedure known as Legendre wavelet spectral collocation method (LWSCM) has been employed to acquire the similar solution. A comparison in the special cases between the published and present results substantiate the obtained solutions. Addition of the lubrication enhances the fluid velocity and reduces the temperature of the nanofluid at the stretchable surface.

Significance of Buongiorno’s model on viscoelastic MHD flow over a heated lubricated surface subject to Joule heating

Lubrication theory has attained attention lately due to its practical applications, such as the formation of thin films, adhesives, and lubrication of components of machines. Jeffrey’s nanofluid flow over the stagnation region past a power-law lubricated surface is presented in this study. Buongiorno’s model is employed to scrutinize the effects of thermophoresis and Brownian motion phenomena with constant wall and prescribed surface temperature (PST) and effects of heat source/sink, chemical reaction, and Joule heating. Due to the continuity of shear stress of fluid-lubricant and velocity at the interface, interfacial conditions are generated. By similarity conversions, ordinary differential equations are obtained and their solutions are computed numerically. For power-law index equaling [Formula: see text], local similarity solutions are calculated by adopting a finite difference scheme, viz. bvp4c in MATLAB. The energy profiles for constant and prescribed temperatures are monitored. The effects of pertinent parameters on the flow, thermal, and mass distributions are scrutinized and illustrated in graphs. Flow field decreases significantly by raising slip parameter as the aptitude of power-law lubricant to improve the velocity of the bulk fluid. The numerical comparison of wall stress and Nusselt number is also presented. The slip and Jeffrey’s material parameters raise the numerical outcomes of the wall shear stress. In addition, increment in Prandtl number enhances the numerical value of the Nusselt number; however, it reduces for relaxation-to-retardation times ratio.

Modeling and simulation for estimating thin film lubrication effects on flow of Jeffrey liquid by a spiraling disk

Advancements in mechanical expertise and rigorous need for gyratory components of machines expedite scientists towards essentiality of the eternal evolution of modified lubricants to corroborate the reliability, innocuous procedure and stability of sundry bearings. To enhance the performances at heftily ponderous load and high velocity, the high molecular polymers are utilized in mechanical bearings as lubricant. These lubricants are non-Newtonian in characteristics and comply with different constitutive relationships. One of them is the power law lubricant which complies with Ostwald model and is broadly utilized for the engineering lubrication. The derivation of the slip-flow conditions at the interface of bulk Jeffrey fluid and the thin layer non-Newtonian lubricant is performed over a disk spiraling with simultaneous radial stretching and rotation. To obtain a homogeneous solution, the power-law index is suggested 1/3 and no-slip boundary condition is converted into an incipient slip boundary condition. A single dimensionless slip parameter is introduced to regulate the velocity slip. Flow equations are obtained, and the similarity conversion is performed to obtain ordinary differential equations. Numerical results are computed to visually perceive the effects of lubrication on the flow field by incorporating the interfacial slip conditions. The presence of the lubrication enhances the fluid velocity and plays major role in the reduction of the skin friction at disk surface.

Lubrication effects on the peristaltic motion of a couple stress fluid in an asymmetric channel

The present article deals with theoretical analysis on the peristaltic transport of a couple stress fluid with lubrication on the walls of the channel. The walls are coated with thin layer of power-law lubricant and the condition arised by the coating is modelled by taking the continuity of velocity and shear stresses of both the fluids at the fluid–fluid interface. The flow problem is discussed in two-dimensional asymmetric medium assuming long wavelength and low Reynolds number. Closed form solutions for velocity, stream function and flow rate are discussed. The numerical solutions for pressure rise, trapping and reflux are discussed. The effects of lubricant parameter, couple stress parameter, phase difference, wave amplitudes and flow rate are discussed for symmetric and asymmetric channels. It is observed that by increasing the lubrication effects, pressure rise increases in the pumping region and for trapping, boluses disappear and streamlines become parallel to the walls of the channel. From the given flow problem, the limiting cases of no-slip and viscous flow are presumed and found to be in excellent agreement with the existing literature.

Stagnation point Walter’s-B nanofluid flow over power-law lubricating surface with slip conditions: Hybrid HAM solutions

Modern bearings used the lubricants having polymer components of larger molecular weight for higher speed and high load operations. These lubricants show rheological activity that is non-Newtonian. Power-law lubricants are commonly used for industrial and bearing lubrication operations. This article is modeled through the slip as interfacial condition to demonstrate the role of power-law lubrication on the stagnation point flow of Walters-B nanofluid. The thermophoretic force and Brownian movement factors are accounted in energy and mass species expressions. The expressions in partial differential forms are constructed for both the base and lubricant fluids. The system is re-structured into ordinary differential expressions by the implication of dimensional analysis. An approximate and numerical scheme namely the hybrid homotopy analysis method is reported to demonstrate the solutions of nonlinear expressions. The behavior of involved constraints on practical quantities is shown and analyzed. The nature of friction factor, thermal and solutal rates at the surface is reported through numeric data. Match of the present solution with previously published data shown better agreement. It can be seen that the slip phenomenon dominates over the free-stream phenomenon. The large values of viscoelastic parameter decay the thermal and solutal fields.

Analysis of a double layer porous hybrid journal bearing considering the combined influence of wear and non-Newtonian behaviour of lubricant

Use of porous materials in fluid film is well established so as to make more uniform distribution of pressure along the journal surface. The work presented in this paper deals with theoretical examination into the effect of worn bearing surface on the behaviour of a hybrid double layer porous journal bearing system (DLPJBS) operating with power-law lubricants. The governing equation for the flow of non-Newtonian lubricant in the bearing porous clearance space is solved by using the FEM. The effects of non-Newtonian lubricant on the bearing characteristics of a worn bearing have been studied. Findings of this study indicates that the hybrid DLPJBS operating under non-Newtonian lubricant offers enhanced values of $${\bar{h}}_{min}$$ , $${\bar{\omega}}_{th}$$ and rotor dynamic coefficients (stiffness and damping coefficients).

Lubrication effects on axisymmetric flow of a micropolar fluid by a spiraling disk

Advances in modern technology and extremely stringent demands for rotating elements of machines impose researchers on the need for the continuous development of improved lubricants to ensure the stability, safe operation, and reliability of various bearings. For operations at high speed and heavy load, modern bearings use lubricants containing high molecular weight polymer components. Such lubricants exhibit non-Newtonian rheological behavior. Power-law lubricant is widely used for the bearings and the industrial lubrication processes. This article is established to estimate the power-law lubrication effects on the Homann flow of a micropolar fluid past a disk with the spiraling motion. A lubrication layer of a non-Newtonian power-law lubricant with negligible thickness is applied between the disk rough surface and the bulk fluid. A new and very complex interfacial boundary condition is derived for the lubricated spiraling disk and is utilized to explore the impact of different flow parameters on the fluid velocity as well as the microrotation. Numerical results are computed for some quantities of physical interest, i.e., radial, azimuthal skin friction coefficients, and the wall shear stress are calculated for various values of the spiral angle, disk spiraling parameter, material parameter, and slip parameter. The addition of slip assists the radial velocity and opposes the azimuthal velocity. The radial velocity is enhanced by increasing the disk spiraling and spiral angle.

Magnetized mixed convection second‐grade fluid flow adjacent to a lubricated vertical surface

AbstractThe aspects of magnetized mixed convection in second‐grade fluid flow near stagnant point induced by vertical wall are reported. The fluid is impinging orthogonally on the power law lubricant surface. The convective surface temperature and concentration distribution have been assumed. Both the lubricant and the base fluid are governed by the partial differential mathematical expressions. The velocity of the second‐grade fluid and the lubricant are supposed to be continuous at interface. To get the solution of defined nonlinear problem, an implicit numerical technique namely Keller‐Box scheme is applied. The influential constraints are visualized by plotting graphs on velocity, concentration, and thermal profiles. The results of skin‐friction factors, and mass and heat transport rates for both opposing and assisting flows are tabulated and evaluated. The obtained results are validated through available data for limiting conditions.

Compressible fluid film lubrication of rollers with thermal effects

The present paper squarely aims to analyze the squeezing velocity of a hydrodynamic lubrication used for symmetric roller bearings. Hydrodynamic compressible fluid film lubrication of cylindrical rollers is here considered under the influence of non Newtonian power law lubricants with squeezing velocity and cavitations. The changes that show up in lubrication consistency due to pressure, density and temperature are shown via ures and tables. Further, pressure, density, temperature, load, traction and coefficient of traction for various consistency index n and normal speeds are calculated and compared with the previous results. Those results are united with the previous findings.

Thermal Effects in Power-Law Fluid Film Lubrication of Rolling/Sliding Line Contact

Hydrodynamic lubrication of heavily loaded rigid system of non-symmetric roller bearings is studied to investigate the thermal effects in the operating behavior of line contact under isothermal and adiabatic boundaries. The incompressible power law lubricant is here considered and its consistency is taken to change with hydrodynamic pressure and the corresponding mean lubricant temperature. The flow controlling equations such as momentum, continuity and thermal energy are solved numerically using R-K Fehlberg method. The results obtained particularly, pressure, mean temperature, load and traction profiles are in good agreement with the previous findings.

Effects of non-Newtonian lubricants and elastic coating on transient elastohydrodynamic lubrication at impact squeeze loading

This study explores the effects of non-Newtonian lubricants on elastohydrodynamic lubrication with coating at impact and rebound loading using power law lubricants. The coupled transient modified Reynolds, rheology, elasticity deformation, and ball motion equations are solved simultaneously, thus obtaining the transient pressure profiles, film shapes, normal squeeze velocities and accelerations. The effect of the flow index ( n) is equivalent to enhancing the lubricant viscosity, also enlarging the damper effect. The simulation results reveal that the film thickness, the primary peak, and the secondary peak increase with increasing the flow index. The greater the flow index is, the earlier the dimple form, and the smaller the maximum value of the impact force is. The rebounding velocity and the peak value of acceleration increase with decreasing the flow index. Moreover, this research possesses academic innovation and industrial application.

Non-Newtonian Lubrication of Asymmetric Rollers with Thermal and Inertia Effects

ABSTRACTThis research work explores the effects of thermal and inertia on hydrodynamic lubrication of asymmetric rigid rollers by incompressible non-Newtonian power law fluids and assesses the contribution of inertia to the system under consideration. The consistency of the power law lubricants is assumed to vary with the pressure and mean film temperature. The governing equations are solved first analytically and then numerically by the Runge-Kutta-Fehlberg method together with some reasonable tolerance. The results obtained confirm that there is significant increase in load and traction due to inertia. In addition, the effect of inertia shifts the pressure peak and the cavitation points toward the left.

A Lubrication Theory for Anisotropic Slips and Flow Rheology

abstractA lubrication theory, considering the coupled effects of anisotropic slip on both the solid–liquid interface and non-Newtonian power law lubricant, is proposed to enhance surface treatment and oil additives. A modified Reynolds equation as well as Poiseuille and Couette flow rate correctors are then derived by applying the rheology model and Navier slip boundary conditions with orthogonal principal slip lengths (, ). Hence, the different slenderness ratios that lead to different performance of journal bearings are used to highlight the coupling effects of anisotropic slips and flow rheology. Contours of constant load ratios are plotted and then the parameters in flow rheology and boundary slip can be located while designing functional surfaces in journal bearings.

A comparative study of full and partial textured hybrid orifice compensated circular thrust pad bearing system

This work concern with the performance of hybrid circular thrust pad bearing having partial and full textured surface, operating with power law lubricant has been studied. The governing Reynolds equation is non-linear with pressure. Finite element method with JFO boundary conditions has been implemented to obtain fluid film pressure on the bearing surface and cavitation zone. The numerically simulated results reveal that, among the different non-Newtonian lubricants, the dilatant one provides the minimum value of frictional power loss. Results show that surface texture and the behavior of lubricant significantly changes the frictional power loss and other performance parameters. It is expected that the result obtained will be very much quite useful for bearing designer and academic community.

A tribological study of piston rings lubricated by power law oils

A 2D axisymmetric hydrodynamic model was developed considering fluid structure interaction analysis in order to solve the Navier–Stokes equations. The effect of lubricants viscosities in terms of both monograde and multigrade oils, on the produced piston ring friction force are compared, using smooth and textured piston rings. The novelty of the current paper is the solution of the Navier–Stokes equations with the use of power law lubricants, which act in non-Newtonian shear for the piston ring friction problem. The lubricant viscosity variation in relation to the temperature has been taken into account. Simulation shows a good prediction at lower loads and higher piston speeds. The hydrodynamic pressure, the oil film thickness and the friction force on smooth and textured flat piston ring are predicted and presented.

POWER LAW FLUID MODEL INCORPORATED INTO THIN FILM ELASTOHYDRODYNAMIC LUBRICATION OF CIRCULAR CONTACTS

The modified Reynolds equation for power-law fluid is derived from the viscous adsorption theory for thin film elastohydrodynamic lubrication (TFEHL) of circular contacts. The lubricating film between solid surfaces is modeled as three fixed layers, which are two adsorption layers on each surface and a middle layer. The differences between classical EHL and TFEHL with power-law lubricants are discussed. Results show that the TFEHL power law model can reasonably calculate the pressure distribution, the film thickness, and the velocity distribution. The thickness and viscosity of the adsorption layer and the flow index significantly influence the lubrication characteristics of the contact conjunction.

A theoretical study of ionic liquid lubricated μ-EHL line contacts considering surface texture

In this paper, the micro-EHL behavior of seven different ionic liquids in textured surface of concentrated engineering contacts is discussed. The surface textures with sinusoid, triangle and saw-tooth waveform with roughness amplitudes equal to asperity heights have been considered. The ionic liquids have been modeled as piezo-viscous power-law lubricants and film thickness, contact pressure and friction force studied for different power law index, material parameter and texture patterns. The results show that the texture pattern and material combinations significantly affect the micro-EHL contact behavior. Lubricating behavior of ionic liquids can be improved by judicious selection of texture and material combinations.

Characterization of lubrication of asymmetric rollers including thermal effects

Purpose– The purpose of this paper is to deal with the qualitative analysis of hydrodynamic lubrication of asymmetric rollers with non-Newtonian incompressible power law lubricants including Newtonian.Design/methodology/approach– The fluid flow governing equations such as equation of motion along with continuity and thermal equations are solved first analytically and investigated numerically by the Runge-Kutta Fehlberg method.Findings– As a result of this work, it is found that there is a significant change in temperature, pressure, load and traction with Newtonian and non-Newtonian fluids.Research limitations/implications– The authors considered incompressible hydrodynamic lubrication of two rigid asymmetric rollers, one of them is assumed to be adiabatic. The convection term of the heat flow equation is taken in its average form.Originality/value– It is a theoretical problem of two heavily loaded rigid cylindrical rollers with cavitations, where the consistency of the power law lubricant is assumed to vary with pressure and the mean film temperature. It has not appeared in the literature.