Squeeze Film Lubrication Research Articles

Effect of Variation in Viscosity on Static and Dynamic Characteristics of Rough Porous Journal Bearings with Micropolar Fluid Squeeze Film Lubrication

In the present study, an effort was made to determine the effects of a porous matrix with different viscosities on the dynamic and static behaviors of rough short journal bearings taking into account the action of a squeezing film under varying loads without journal rotation. The micropolar fluid was regarded as a lubricant that contained microstructure additives in both the porous region and the film region. By applying Darcy’s law for micropolar fluids through a porous matrix and stochastic theory related to uneven surfaces, a standardized Reynolds-type equation was extrapolated. Two scenarios with a stable and an alternating applied load were analyzed. The impacts of variations in viscosity, the porous medium, and roughness on a short journal bearing were examined. We inspected the dynamic and static behaviors of the journal bearing. We found that the velocity of the journal center with a micropolar fluid decreased when there was a cyclic load, and the impact of variations in the viscosity and porous matrix diminished the load capacity and pressure in the squeeze film and increased the velocity of the journal center.

Theoretical analysis of effect of MHD, couple stress and slip velocity on squeeze film lubrication of rough Triangular plates

In this study, Christensen's stochastic theory is utilized on rough surfaces' hydrodynamic lubricating effect to examine how surface roughness, couple stress fluid, slip velocity, magnetohydrodynamic (MHD), and the triangular surface interact. Modified Reynolds equation is derived analytically using combining theories of Stokes couple stresses, Lorentz forces, and Christensen's stochastic hypothesis about hydrodynamic lubrication. Pressure, load carrying capacity and squeeze film time expression is derived mathematically using Reynolds equation that accounts for surface roughness and coupling stress. For various parameters including rough parameter, slip velocity, Hartmann number, and couple stress, the lubricating characteristics are analysed graphically. Squeeze film time, load carrying capacity, and pressure are enhanced by an increase in slip velocity, couplestress and magnetic field. The lubrication characteristics decreases (increases) on squeeze film pressure, load carrying capacity and squeeze film time through increasing values of the longitudinal (transverse) roughness parameter.

Influence of magneto-hydrodynamic and couple stress squeeze film lubrication on conical bearing-a slip velocity model

This paper explores the impact of MHD couple stress and slip velocity over a conical bearing in the presence of magnetic field. The flow is considered as incompressible. A uniform magnetic field is imposed perpendicular to the bearing alongy-axis. The modified Reynolds equation is solved using appropriate boundary conditions in dimensionless form to find the pressure distribution which is then used to obtain the expression for load carrying capacity paving the way for the calculation of response time. Numerical computations of the results show that the MHD couple stress on the conical bearings indicates that enhances the pressure distribution, load carrying capacity and squeeze film time of the conical bearings. Further, decrease in these characteristics was observed for the increased values of slip velocity and cone angle.

Effect of magnetic field and slip velocity on the performance of bearings lubricated by couple stress fluid on long cylinder and infinite plate — A theoretical analysis

In this research, the combined effect of magnetohydrodynamics (MHD) and slip velocity on squeeze film lubrication of long cylinders and infinite plates with couple stress fluid has been studied. Combining the Stokes couple stress theory and the Lorentz force theory yields analytical solutions for the modified Reynolds equation. Using the Reynolds equation, the mathematical expressions for squeeze film pressure, load-carrying capacity and squeeze film time are obtained. The pressure, load carrying capacity and squeeze film time increase with the combined effect of MHD, couple stress fluids and slip velocity.

Semi-analytical approach-based studies of the squeeze film lubrication between rough porous annular discs: Rabinowitsch fluid model

In recent years, there has been much interest in the effects of porosity and surface roughness (SR) or geometric irregularities between two moving plates under hydrodynamic lubrication. Porous bearings are used extensively in wide range of equipment, including computers, office equipment, home appliances, electric motors, and vehicles. In light of the importance of the aforementioned applications, we explored how SR and porous materials affect annular discs under the condition of a squeeze film. A five-point Gauss quadrature integral formula has been used to examine the characteristics of annular discs and a small perturbation method has been used to discretise the governing Rabinowitsch fluid flow (RFF) equations. The impact of nonlinear parameters on the behaviour of porosity and SR have been visualised in terms of film pressure (FP), load carrying capacity (LCC), and squeeze response time (SRT) of annular discs. Under the conditions of pseudoplastic and dilatant fluids, the effects of SR and porous materials between annular discs have been estimated in the form of the film pressure, LCC, and SRT and are presented in this manuscript as tables and graphs. According to the findings, the performance of an annular disc is significantly affected by porous material and radial roughness patterns. In addition, when RFF is carried through a rough surface and porous media, the performance is found to improve for dilatant fluids but suffer for pseudoplastic fluids.

Magnetohydrodynamics and viscosity variation in couple stress squeeze film lubrication between rough flat and curved circular plates

A simplified mathematical model has been developed for understanding combined effects of surface roughness, viscosity variation and couple stresses on the squeeze film behaviour of a flat and a curved circular plate in the presence of transverse magnetic field. The Stokes (1966) couple stress fluid model is included to account for the couple stresses arising due to the presence of microstructure additives in the lubricant. In the context of Christensen’s (1969) stochastic theory for the lubrication of rough surfaces, two types of one-dimensional roughness patterns (radial and azimuthal) are considered. The governing modified stochastic Reynolds type equations are derived for these roughness patterns. Expressions for the mean squeeze film characteristics are obtained. Numerical computations of the results show that the azimuthal roughness pattern on the curved circular and flat plate results in more pressure buildup whereas performance of the squeeze film suffers due to the radial roughness pattern. Further the Lorentz force characterized by the Hartmann number, couple stress parameter and viscosity variation parameter improve the performance of the squeeze film lubrication as compared to the classical case (Non-magnetic, Newtonian case and non-viscous case).

Theoretical analysis of effect of MHD, couple stress and slip velocity on squeeze film lubrication characteristics of Long Cylinder and Infinite Rough Plate

The current research examines how a long cylinder, and an infinitely flat surface are affected by surface roughness, MHD, couple stress, and slip velocity using the stochastic theory of hydrodynamic lubrication of rough surfaces as developed by Christensen. Squeeze film time, load carrying capacity, and pressure are calculated using a derived mathematical form of Reynolds' modified equation that accounts for surface roughness and coupling stress. The amount of time needed to squeeze a film under a specific pressure and load can be determined using an analytical method called Reynolds' equation. The lubrication characteristics are graphically represented for various parameters. When a magnetic field occurs and the slip velocity increases, the pressure of the squeeze film, its capacity to carry loads, and the time it takes are all significantly increased. The lubricating properties caused a decrease or increase in the values of the longitudinal (transverse) roughness parameter.

Mathematical Model to Study the Squeeze Film Characteristics of Diseased Human Synovial Knee Joint

Synovial fluid functions as a biological lubricant and lubricates articular cartilage to reduce friction and wear. Lubricin and hyaluronic acid are the primary components of synovial fluid responsible for its lubricating properties. The loss of properties in synovial fluid and articular cartilage due to aging and activities can restrict mobility in synovial joints, resulting in the degradation of articular cartilage and ultimately leading to pathological synovial joints, which is a major cause of disability. Thus, research on synovial joints remains crucial, and despite previous investigations on synovial joint lubrication, there are several issues related to squeeze film lubrication that require further attention. The Newtonian model of squeeze film lubrication in synovial joints needs to be extensively studied. In this study, lubrication and other related properties of synovial fluid are studied theoretically. In this paper, we have studied the flow of synovial fluid in the diseased synovial joint. Further, we have studied the effect of the viscosity of the synovial fluid, the permeability of articular cartilage, thickness of articular cartilage, and fluid film thickness on the characteristic of the squeeze film formed between the articular cartilages of the diseased human knee joint. The flow of synovial fluid is modeled by considering it as a viscous, incompressible and Newtonian fluid. We have derived the modified Reynolds equation using the principle of hydrodynamic lubrication and continuum mechanics theory and solved it by applying the suitable boundary conditions according to the physical considerations. Subsequently, we obtained the expression for pressure distribution in fluid film, load-bearing capacity, and squeeze time and have done the theoretical analysis on these properties for different parameters. Pressure increases with squeeze velocity and viscosity of the synovial fluid and decreases with permeability and fluid film thickness. Human knee joint becomes diseased due to excessive pressure, and the mobility of the knee joint decreases. The load capacity increases with viscosity and squeeze velocity and decreases with permeability resulting in the reduction of the load-carrying capacity of the knee joint in diseased conditions. Moreover, the squeeze time also increased in the diseased state of the joint.

Electrical Contact During a Rolling Vibratory Motion Considering Mixed Lubrication

Abstract In many devices and applications, electrical contacts are exposed to vibrations, sliding, or rolling conditions and are prone to fretting-based degradation. Thus, lubricants are often employed in such contacts to reduce sliding wear and fretting corrosion. However, due to the non-conductive behavior of the lubricants with fluorocarbons and hydrocarbons, lubricants lead to a few adverse problems. Also, the fluid dynamics upon excitation, vibration, or sliding causes extended breaks or gaps in between the conducting surfaces. In reality, this can be noticed during vibrations occurring as a result of earthquakes or technical personnel maintenance. This could also have applications to electrified rolling element bearings. Factors such as surface roughness and fluid viscosity will determine the time taken for the two surfaces of the connectors to separate from a solid conductive contact. In this work, a coupled structural–fluid theoretical model is developed for evaluating such intermittent contact breaks/gaps when two metallic rough surfaces in contact are under vibrations. The model is capable of predicting the increase in the fluid film as well as the contact resistance change with time due to the possible connector vibration. The experimentally observed rocking vibration mode seen in connectors and the time-dependent squeeze film lubrication effect are also considered.

Study about the characteristics of squeeze film between rough porous curved annular plates in the presence of micropolar fluids

This article examines the impact of micropolar fluids on the squeeze film lubrication between rough porous curved annular plates. The mean squeeze film pressure, mean load bearing capacity, and squeezing time film are evaluated for two forms of rough surface patterns (radial and azimuthal) by deriving the stochastic Reynolds equation. The squeeze film properties are found to decrease (increase) the radial (azimuthal) roughness patterns.

Numerical examination of wall properties for the magnetohydrodynamics stagnation point flow of micro-rotating fluid subject to weak concentration

In this investigation, stagnation point flow of non-Newtonian fluid is considered under the impact of magnetohydrodynamics, porous medium, and mixed convection effects. Additionally, angular momentum and energy transport constitutive equations are also taken into account in order to explore the fluid micro-rotational effects. The fluid motion develops by virtue of linear stretching and slip factors. Furthermore, the energy transport equation is raised with the effect of viscous dissipation and heat source phenomena. Mathematical formulations lead to a set of ordinary differential equations by introducing similarity variables. The proposed model has been solved numerically using fourth-order Runge–Kutta method with shooting technique. Influence of pertinent flow parameters for the case of weak concentration of micro-elements on velocity, temperature, skin friction, and local heat flux at the surface is computed and discussed. Different ranges are chosen for the flow parameters, for example; magnetic field variation is taken [0, 0.9], micro-rotation [0,1], stretching ratio [0,0.2], surface condition [0,1], the Prandtl number [3, 12], and the Eckert number [3, 11]. The fluid velocity slows down when the magnetic number varies from 0.0 to 0.5 in the presence of weak concentration (m = 0.5) of micro-elements. In addition, the maximum increasing percentage of skin friction is obtained when the porosity parameter varies from 0.0 to 0.6. The maximum decreasing percentage of the Nusselt number is obtained when the thermal slip parameter varies from 0.0 to 0.8. The current study has multiple fascinating applications in polymeric solutions, bio-medical functions like magnetic drug targeting, heat conduction in tissues, surface roughness, and squeeze film lubrication problems between conical bearings.

Effect of Significant Parameters on Squeeze Film Characteristics in Pathological Synovial Joints

Synovial joints are unique biological tribo-systems that allow for efficient mobility. Most of the synovial joint activities in the human body are accomplished due to the presence of synovial fluid. As a biological lubricant, synovial fluid lubricates the articular cartilage to minimize wear and friction. The key components of synovial fluid that give it its lubricating ability are lubricin, hyaluronic acid (HA), and surface-active phospholipids. Due to age and activities, synovial fluid and articular cartilages lose their properties, restricting synovial joint mobility and resulting in articular cartilage degradation, leading to the pathological synovial joint, which is a major cause of disability. In this context, synovial joint research remains significant. Even though synovial joint lubrication has been investigated, several problems linked to squeeze film lubrication need greater attention. The Newtonian model of squeeze film lubrication in synovial joints must be studied more extensively. This work aims to investigate squeeze film lubrication in diseased synovial joints. The lubrication and other properties of synovial fluid and the flow of synovial fluid in a diseased human knee joint are investigated theoretically in this work. We have investigated the effect of the synovial fluid viscosity and the effects of permeability and thickness of articular cartilage on squeeze film properties. Moreover, we have also investigated the effect of squeeze velocity and film thickness on the characteristics of the squeeze film formed between the articular cartilages of a diseased human knee joint. In this work, the articular cartilages were treated as a rough, porous material, and the geometry was approximated as parallel rectangular plates, while the synovial fluid flow is modeled as a viscous, incompressible, and Newtonian fluid. The modified Reynolds equation is obtained using the principles of hydrodynamic lubrication and continuum mechanics, and it is solved using the appropriate boundary conditions. The expressions for pressure distribution, load-bearing capacity, and squeezing time are then determined, and theoretical analysis for various parameters is conducted. Pressure is increased by squeeze velocity and viscosity, while it is decreased by permeability and film thickness, leading to an unhealthy knee joint and a reduction in knee joint mobility. The load capacity of the knee joint decreases with permeability and increases with viscosity and squeezing velocity, resulting in a reduction in the load-carrying capacity of the knee joint in diseased conditions. Synovial knee joint illness is indicated by increased pressure and squeeze time. The squeeze film properties of synovial joints are important for maintaining joint health and function. Joint diseases such as osteoarthritis, rheumatoid arthritis, and gout can affect the composition and production of synovial fluid, leading to changes in squeeze film properties and potentially causing joint damage and pain. Understanding these relationships can help in the development of effective treatments for joint diseases.

Ferrofluid squeeze film lubrication: surface roughness effect

PurposeThis study aims to investigate the combined effects of roughness and ferrofluid lubricant on finite journal bearing load capacity and squeeze time.Design/methodology/approachThe stochastic theory of Christensen is applied to study the surface roughness effect. The Shliomis model is used to take into account the effects of the rotational viscosity of ferromagnetic particles and their magnetic moment. A finite wire located in the center of the shaft produces the applied magnetic field. A developed computing code allows predicting the effect of the surface roughness on the performance of the considered journal bearing. The good agreement with the results of the literature validates the used approach.FindingsThis study shows that unlike longitudinal roughness, the presence of transverse roughness makes the use of ferrofluid more beneficial in terms of increasing the performance of finite journal bearings. This increase is more significant for large relative eccentricities, which present an ideal confinement.Originality/valueThis study shows the effect of two surface roughness patterns on the squeezing performance of a finite journal bearing lubricated by a ferrofluid.

MICROPOLAR FLUID LUBRICATION OF FINITE ROUGH POROUS JOURNAL BEARING WITH SQUEEZING EFFECT

In this paper, a theoretical analysis of the effect of surface roughness on the squeeze film lubrication of finite porous journal bearings with micropolar fluids is studied. A more generalized form of surface roughness is mathematically modeled by a stochastic random variable with non-zero mean, variance and skewness. The generalized average Reynolds type equation is derived for the squeeze film lubrication of finite rough porous journal bearings with micropolar fluids as lubricant. The closed form expressions are obtained for the fluid film pressure, load carrying capacity, journal centre velocity and locus of the journal centre. The cases of a constant applied load and an alternating applied load are analyzed under a cyclic load the micropolar fluids provide a reduction in the journal centre velocity. Further, it is numerical computations of the results show that the negatively skewed surface roughness pattern increase fluid film pressure, load carrying capacity and decreases the journal centre velocity. Where as adverse effects were found for the positively skewed surface roughness pattern. The effect of porous parameter causes reduction in fliud film pressure, load carrying capacity and enhances the journal centre velocity.

Magnetohydrodynamic Micropolar Fluid Squeeze Film Lubrication between Stepped Porous Parallel Plates

Objectives: The primary goal of this paper is to study the influence of MHD and micropolar fluid on the squeeze film lubrication between stepped porous parallel plates. Method: The non-Newtonian micropolar fluid MHD Reynolds type equation is derived by considering the flow of micropolar fluid in the porous matrix as described by Darcy’s law, as well as microstructure additives and magnetic effects associated with the magnetization of the fluid. The numerical solutions are presented graphically for the MHD squeeze film characteristics for various values of coupling number parameter, characteristic material length, and magnetic Hartmann number. Findings: According to the results, the micropolar fluid and the magnetic effects significantly influence the squeeze film characteristics. Comparing the MHD micropolar fluid impact on the squeeze film lubrication with the corresponding Newtonian and non-magnetic cases, we observe that there is a significant increase in the approaching time and the load-carrying capability. The increase in the step height decreases the squeezing film time. Novelty: The original research was conducted on the magneto-hydrodynamic micropolar fluid squeeze film lubrication between stepped porous parallel plates which has not been studied so far. The effect of applied magnetic field is to enhance the load carrying capacity and delayed time of approach which are the most desirable characteristics for improving the bearing performance. Keywords: Squeeze Film; Stepped plates; Magnetohydrodynamic; Porous; Micropolar

A comparative study of ferrofluid lubrication on double-layer porous squeeze curved annular plates with slip velocity

This article makes an effort to present a comparative study on the performance of a Shliomis model-based ferrofluid (FF) lubrication of a porous squeeze film in curved annular plates taking slip velocity into account. The modified Darcy’s law has been adopted to find the impact of the doublelayered porosity, while the slip velocity effect has been calculated according to Beavers and Joseph’s slip conditions. The modified Reynolds equation for the double-layered bearing system is solved to compute a dimensionless pressure profile and load-bearing capacity (LBC). The graphical results of the study reveal that the LBC increases in the case of magnetization, volume concentration and upper plate’s curvature parameter while it decreases with other parameters for both the film thickness profile. A comparative study suggests that the exponential film thickness profile is more suitable to enhance LBC for the annular plates lubricated by ferrofluid, including the presence of a slip. The study shows that the slip model performed quite well and there is a potential for improving the performance efficiency. Besides, multiple methods have been presented to enhance the performance of the above mentioned bearing system by selecting various combinations of parameters governing the system.

Combined effect of circumferential roughness and squeeze velocity on ferrofluid squeeze film with rotating sphere and rough plate

Based on the Jenkins model for ferrofluid flow regarding the performance of squeeze-film lubrication between rotating upper spherical surface and circumferentially rough lower plate is presented. Here, for hydrodynamic lubrication, we have adopted the ferrohydrodynamic theory. Further, using Christensen’s stochastic model, surface roughness is examined. In the paper, in the presence of a radially variable magnetic field, rotations of both the upper and lower surfaces as well as roughness of the surface, the Reynolds type equation for the squeeze-film bearing is established. By using the Reynolds type equation, expressions for the non-dimensional film pressure and load-carrying capacity are obtained for circumferential roughness pattern. Neuringer–Rosensweig (NR) model results are computed using the Jenkins model. The results show that non-dimensional film pressure increases remarkably when the non-dimensional radial parameter ( R) increases. Also, as the nominal minimum film thickness increases, load-carrying capacity decreases in the Jenkins model. However, as a result of Tables 5 and 6, the non-dimensional load-carrying capacity of the Jenkins model is improved compared to that of the NR model.

Numerical investigation of squeeze film lubrication on bioinspired hexagonal patterned surface

PurposeThis paper aims to investigate the squeeze film lubrication properties of hexagonal patterned surface inspired by the epidermis structure of tree frog’s toe pad and numerically explore the working mechanism of hexagonal micropillar during the acquisition process of high adhesive and friction for wet contacts.Design/methodology/approachA two-dimensional elastohydrodynamic numerical model is employed for the squeezing contacts. The pressure distribution, load carrying capacity and liquid flow rate of the squeeze film are obtained through a simultaneous solution of the two-dimensional Reynolds equation and elasticity deformation equations.FindingsHigher pressure is found to be longitudinally distributed across individual hexagonal pillar, with pressure peak emerging at the center of hexagonal pillar. Expanding the area density and shrinking the channel depth or initial film thickness will improve the magnitude of squeezing pressure. Relatively lower pressure is generated inside interconnected channels, which reduces the load carrying capacity of the squeeze film. Meanwhile, the introduction of microchannel is revealed to downscale the total mass flow rate of squeezing contacts.Originality/valueThis paper provides a good proof for the working mechanism of surface microstructures during the acquisition process of high adhesive and friction for wet contacts.

Ferro-nanofluid squeeze film lubrication with heat transfer

A theoretical study of a squeezing ferro-nanofluid flow including thermal effects is carried out with application to bearings and articular cartilages. A representational geometry of the thin layer of a ferro-nanofluid squeezed between a flat rigid disk and a thin porous bed is considered. The flow behaviours and heat transfer in the fluid and porous regions are investigated. The mathematical problem is formulated based on the Neuringer–Rosensweig model for ferro-nanofluids in the fluid region including an external magnetic field, Darcy law for the porous region and Beavers–Joseph slip condition at the fluid–porous interface. The expressions for velocity, fluid film thickness, contact time, fluid flux, streamlines, pathlines, mean temperature and heat transfer rate in the fluid and porous regions are obtained by using a perturbation method. An asymptotic solution for the fluid layer thickness is also presented. The problem is also solved by a numerical method and the results by asymptotic analysis, perturbation and numerical methods are obtained assuming a constant force squeezing state and are compared. It is shown that the results obtained by all the methods agree well with each other. The effects of various parameters such as Darcy number, Beavers–Joseph constant and magnetization parameter on the flow behaviours, contact time, mean temperature and heat transfer rate are investigated. The novel results showing the impact of using ferro-nanofluids in the two applications under consideration are presented. The results under special cases are further compared with the existing results in the literature and are found to agree well.

Stochastic Reynolds equation for the combined effects of piezo-viscous dependency and squeeze-film lubrication of micropolar fluids on rough porous circular stepped plates

The aim of this paper is to presents a theoretical analysis on squeeze-film characteristics of a rough porous circular stepped plate in the vicinity of pressure-dependent viscosity and lubrication by micropolar fluids. A closed-form expression for non-dimensional pressure, load, and squeezing time is derived based on Eringen’s theory, Darcy’s equation, and Christensen’s stochastic approach. Results indicate that the effects of pressure-dependent viscosity, surface roughness, and micropolar fluids play an important role in increasing the load-carrying capacity and squeezing time, whereas the presence of porous media decreases the load-carrying capacity and squeezing time of the rough porous circular stepped plates.