Squeeze Film Characteristics Research Articles

Effects of fluid inertia forces in ferrofluid lubricated circular stepped squeeze films – Shliomis model

Purpose This paper aims to study the inertia squeeze film characteristics between ferrofluid-lubricated circular stepped disks. Owing to the development of modern machine systems, the application of ferrofluids has received great attention. Because the circular disks are a special situation of circular stepped squeeze films, a further study of fluid inertia force effects on the ferrofluid-lubricated circular stepped squeezing mechanism is motivated. Design/methodology/approach On the basis of the ferrohydrodynamic flow model of Shliomis incorporating the momentum integral method, the effects of fluid inertia forces in ferrofluid-lubricated circular stepped squeeze films in the presence of external magnetic fields are investigated in this study. Analytical solutions of squeeze film performances are derived. Findings The fluid inertia force effects provide an increased load capacity and a longer squeeze film time for the ferrofluid-lubricated circular stepped squeeze film, especially for a larger value of the inertia parameter, the Langevin parameter and the volume concentration and a smaller value of the radius ratio and the step height ratio. Originality/value For engineering applications, numerical tables for squeeze film loads of circular stepped disks are also provided in this paper.

Squeeze film characteristics of conical bearings with combined effects of piezo-viscous dependency and non-Newtonian couple stresses

In this paper, the analysis of squeeze film characteristics of conical bearings with combined effects of piezo-viscous dependency and couple stress fluid is presented. On the basis of the Stokes microcontinuum theory of couple stress fluid model and Barus experimental research, a modified Reynolds equation is derived, the standard perturbation technique is used to solve the highly non-linear Reynolds equation and approximate analytical solution is obtained for the squeeze film pressure, load carrying capacity and squeeze film time. According to the results obtained, the effect of viscosity pressure dependency on the squeeze film lubrication of conical bearings with couple stress fluids is to improve the load carrying capacity significantly and lengthen the squeeze film time as compared to iso-viscous Newtonian case.

Influence of the Disturbance Frequency on the Dynamic Characteristics of an Ultrasonic Gas Squeeze Film

ABSTRACTDynamic characteristics of an air ultrasonic squeeze film are affected by disturbance of the levitating object. A completely analytical model for the dynamic characteristics of the air squeeze film taking into consideration the effects of the disturbance acting on the levitating object was established by using compressible gas hydrodynamic lubricating theory. The models were solved by nonlinear numerical methods. Dynamic characteristics of the air squeeze film at specific cases were obtained and the effects of the disturbance amplitude and frequency on dynamic characteristics were discussed. It is found that these influences are significant. Experiments on stiffness and damping coefficients of the squeeze film measurement were carried out. The results showed some discrepancy with the theoretical values.

On the ferrofluid lubricated squeeze film characteristics between a rotating sphere and a radially rough plate

Ferrofluid lubricated squeeze film bearing design system formed by a rotating upper spherical surface and a radially rough lower flat plate considering variable magnetic field, which is oblique to the lower plate, have been analyzed. The variable magnetic field is important because of its advantage of generating maximum field at the required active contact zone. The problem is motivated because squeeze film behaviour is widely observed in many industrial applications like in machine tools, gears, rolling elements, hydraulic systems, engines, clutch plates, force pendulum apparatus, etc. Moreover, the squeeze film behaviour is also observed in skeletal joints of human body. On the basis of ferrohydrodynamic theory and Christensen’s stochastic theory for hydrodynamic lubrication of rough surfaces, the modified Reynolds equation is derived and expressions for squeeze film characteristics are obtained which are calculated numerically and interpreted. While deriving Reynolds equation effects of various parameters like rotation, width of the nominal minimum film thickness and squeeze velocity are also considered.

Non-Newtonian inertial magnetohydrodynamic porous squeeze film lubrication between circular discs

This paper presents a numerical investigation of porous squeeze film between two circular discs of couple stress conducting lubricant in the presence of externally applied magnetic fields taking into account fluid inertia forces. The latter are considered using the reduced Navier–Stokes equations. The fluid flow within the porous disc is modeled by the modified Darcy law. The governing equations are resolved by successive over relaxation method in a sequential coupling algorithm. From the results obtained, the influence of transverse magnetic field, inertia forces and couple stress are to improve the porous squeeze film characteristics.

On the squeeze film characteristics between a sphere and a flat porous plate using ferrofluid

The ferrofluid (FF) lubricated bearing design system formed by upper spherical surface and a flat porous plate considering variable magnetic field, which is oblique to the lower plate, has been analyzed. The porous plate is considered because of having its advantageous property of self-lubrication. The analytical model with squeeze behavior of the phenomenon is developed, considering the validity of Darcy's law in the porous region, using equation of continuity, and equations from ferrohydrodynamics theory. The expressions for squeeze film characteristics are obtained and calculated numerically. The results indicate the better performance of the system, when FF is used as lubricant.

Combined effects of piezo – viscous coupled stress lubricant and rotational inertia upon squeeze film performance of rough circular discs

Purpose – The purpose of this paper is to investigate squeezing and rotating motions between two rough parallel circular discs lubricated by piezo – viscous couple stress lubricant with pressure-dependent viscosity variation. Design/methodology/approach – Based upon the Stokes couple stress theory, Barus viscosity-pressure dependency relation and Christensen rough surfaces model, squeeze film characteristics between two rough parallel circular discs are obtained. Findings – According to the results, it is found that, the combined effects of couple stresses and viscosity-pressure dependency increases squeeze film performance with respect to the classical Newtonian iso-viscous (constant viscosity) lubricant. However, increasing the rotational inertia parameter reduces squeeze film characteristics. On the other hand, depending on the structure of surface roughness, the squeeze film characteristics can be increased or decreased. Furthermore, results show that the surface roughness with circular pattern increases squeeze film characteristics, while the surface roughness with radial pattern will decrease it. Originality/value – This paper is relatively original and describes the squeeze film characteristics between two parallel circular discs with viscosity-pressure dependency, rotational inertia, couple stresses and surface roughness effects.

Effect of pressure dependent viscosity on squeeze film characteristics of micropolar fluid in convex curved plates

Effect of pressure dependent viscosity on squeeze film characteristics of micropolar fluid in convex curved plates

Effect of pressure dependent viscosity on squeeze film characteristics of micropolar fluid in convex curved plates

In this paper, the effect of pressure dependent viscosity on the squeeze film characteristics between convex curved plates of a cosine form is presented. Micropolar fluid theory, which is a possible non-Newtonian model of a suspension of rigid particle additives, is applied to the study of the lubrication of cosine form convex curved plates. The modified Reynolds equation is solved for the fluid film pressure and then the cosine form by considering the exponential relationship in the viscosity variation. For iso-viscous lubricants, the effects of pressure dependent viscosities signify an increase in the values of the squeeze film pressure, the load capacity and the elapsed time. It provides useful information in designing the mechanisms of squeeze film plates for engineering application.

Investigation of Combined Effects of Rotational Inertia and Viscosity–Pressure Dependency on the Squeeze Film Characteristics of Parallel Annular Plates Lubricated by Couple Stress Fluid

This study presents combined effects of couple stress fluids and rotational inertia together with considering lubricant viscosity variation with pressure in squeeze film characteristics of parallel annular plates. Squeeze film characteristics are obtained by combined solution of modified Reynolds equation and Stoke's microcontinuum for couple stress fluids with consideration of viscosity variation with pressure. Various cases of couple stress, inertial, and noninertial characteristics with isoviscous and piezoviscous contributions are investigated. The pressure distribution and load-carrying capacity for lubricant film are obtained in a closed form, using a small perturbation method. Furthermore, numerical solution of the film height versus response time is calculated employing the fourth-order Runge–Kutta method. The result shows that the combined effects of couple stresses and viscosity–pressure dependency improve the load-carrying capacity and lengthen the response time, as compared to the classical Newtonian lubricant with constant viscosity. However, increasing rotational inertia parameter decreases squeeze film characteristics.

Non-Newtonian Inertia Squeeze Film Characteristics in Rectangular Stepped Plates

A study of non-Newtonian inertia squeeze film in rectangular stepped plates has been presented in this paper. Applying the momentum integral method incorporating the micro-continuum theory of non-Newtonian fluids, a non-Newtonian inertia lubrication equation is derived. It is found that the fluid inertia effects yield in a higher normal load capacity as well as a longer squeeze film time as compared to the non-Newtonian stepped squeeze film in the absence of fluid inertia forces.

Modified Reynolds Equation for Different Types of Finite Plates with the Combined Effect of MHD and Couple Stresses

We make an effort to analyze the behavior of squeeze film characteristics of different finite plates with couple stress fluid in the presence of a transverse magnetic field. On the basis of the Stokes couple stress fluid model and hydromagnetic flow model, a modified Reynold's equation is derived, which is solved by using appropriate boundary conditions to obtain squeeze film pressure, load-carrying capacity, and squeeze film time. The graphical representation of the results suggests that the different bearing systems register an enhanced performance with couple stresses compared to that of a bearing system working with a conventional lubricant in the presence of a transverse magnetic field. It is observed that the effect of applied magnetic field on the squeeze film lubrication between different finite plates with conducting couple stress fluids is to increase the load-carrying capacity significantly and to delay the time of approach compared to the corresponding nonconducting Newtonian case. It is seen that for all of the finite plates of different shapes, the circular shape gives the maximum load and time.

Combined effects of fluid inertia forces and non-Newtonian rheology in circular stepped squeeze film disks

Based on the Stokes microcontinuum fluid model together with the averaged inertia principle, the combined effects of fluid inertia forces and non-Newtonian rheology on the squeeze film characteristics between circular stepped disks have been presented in this paper. Comparing with the case of a Newtonian lubricant without inertia forces, the influences of convective inertia forces and non-Newtonian couple stresses provide an increase in values of the load-carrying capacity and the approaching time. The improved performances are more pronounced for stepped squeeze films operating with a larger density parameter and couple stress parameter, and a smaller step height ratio and radius ratio.

Effects of circumferential and radial rough surfaces in a non-Newtonian magnetic fluid lubricated squeeze film

The effects of surface roughness in circular squeeze film disks lubricated with a non-Newtonian magnetic fluid are investigated in this paper. Employing the stochastic model together with the microcontinuum theory and the ferromagnetic flow model, a non-Newtonian magnetic-fluid lubricated Reynolds equation including the influences of rough surfaces is derived, and applied to predict the squeeze film performances. According to the results, the surface roughness effects of circumferential structures increase the mean load capacity and lengthen the mean approaching time as compared to those of the smooth disks with a non-Newtonian magnetic fluid. However, the radial roughness patterns yield a reversed trend. In addition, the effects of rough surfaces on the squeeze film characteristics are more pronounced for circular disks operating with larger values of the surface roughness parameter, the non-Newtonian couple stress parameter, the volume concentration parameter and the magnetic Langevin parameter.

Effects of pressure-dependent viscosity variation on the squeeze film lubrication between a sphere and a rough flat plate with couple stress fluids

In this paper, a theoretical study of the combined effects of surface roughness and the variation of viscosity with pressure on the squeeze film lubrication between sphere and a flat plate is presented. Based on the Christensen’s stochastic theory for the hydrodynamic lubrication of rough surfaces, two types of one-dimensional surface roughness (radial and azimutal) patterns are considered. The generalized averaged Reynold’s equation for Stokes couple stress fluids accounting for the pressure dependent viscosity is mathematically derived for the problem under consideration. The standard perturbation technique is used to solve the averaged nonlinear Reynold’s equation and an approximate analytical solution for the fluid film mean pressure is obtained for the two types of one-dimensional roughness patterns. It is found that, the effects of couple stresses and pressure dependent viscosity variation are to improve the squeeze film characteristics.

Effect of Surface Roughness on the Squeeze Film Characteristics of Circular Plates in the Presence of Conducting Couplestress Fluid and Transverse Magnetic Field

The combined effect of surface roughness and magnetic field on the performance characteristic of the circular plates lubricated with conducting couplestress fluid (CCSF) has been studied. On the basis of the Christensen Stochastic model, the generalized stochastic Reynold’s equation is derived. Modified equations for the nondimensional pressure, load load-carrying capacity, and squeeze film time are derived. The results are presented both numerically and graphically and compared with conducting smooth surface case. It is observed that the surface roughness effects are more pronounced for couplestresses as compared to nonconducting Newtonian fluid (NCNF) in the presence of magnetic field.

MAGNETO-HYDRODYNAMIC NON-NEWTONIAN CURVED CIRCULAR SQUEEZE FILMS

The squeeze film performances between curved circular plates lubricated with an electrically conducting non-Newtonian fluid in the presence of external magnetic fields are investigated in this paper. Based upon the magneto-hydrodynamic flow theory together with the Stokes microcontinuum theory, the magneto-hydrodynamic non-Newtonian Reynolds equation is derived and applied to predict the curved circular squeeze film behaviors. Comparing with the hydrodynamic Newtonian case, the squeeze film characteristics for curved circular plates are improved by the use of an electrically conducting non-Newtonian fluid in the presence of external magnetic fields. Numerical values of the load capacity and the approaching time are provided in Tables for engineering applications.

Magnetohydrodynamic (MHD) squeeze film characteristics between finite porous parallel rectangular plates with surface roughness

Purpose – The purpose of this paper is to consider magnetohydrodynamic (MHD) squeeze film characteristics between finite porous parallel rectangular plates with surface roughness. Design/methodology/approach – Based upon the MHD theory, this paper analyzes the surface roughness effect squeeze film characteristics between finite porous parallel rectangular plates lubricated with an electrically conducting fluid in the presence of a transverse magnetic field. Findings – It is found that the magnetic field effects characterized by the Hartmann number produce an increased value of the load carrying capacity and the response time as compared to the classical Newtonian lubricant case. The modified averaged stochastic Reynolds equation governing the squeeze film pressure is derived. Research limitations/implications – The present study has considered both Newtonian fluids and non-Newtonian liquids. Practical implications – The work represents a very useful source of information for researchers on the subject of MHD squeeze film with finite porous parallel rectangular plates lubricated with an electrically conducting fluid. Originality/value – This paper is relatively original and illustrates the squeeze film characteristics between finite porous parallel rectangular plates with MHD effects.

Fluid inertia force effects in hydromagnetic sphere-plate squeeze films

This paper investigates the influences of fluid inertia forces in hydromagnetic sphere-plate squeeze films. Applying the averaged inertia principle, a megnetohydrodynamic pressure gradient equation has been derived. From the results obtained, the combined effects of fluid inertia forces and electrical conducting fluids in the presence of external magnetic fields provide better squeeze film characteristics, and lengthen the operating life of the sphere-plate system as compared to the non-inertia non-conducting-fluid case.

Effect of surface roughness on magneto-hydrodynamic squeeze-film characteristics between a sphere and a porous plane surface

Purpose– The purpose of this article is to analyse the effects of surface roughness on the magneto-hydrodynamic (MHD) squeeze-film characteristics between a sphere and a porous plane surface, which have not been studied so far.Design/methodology/approach– The analytical model takes into account the effect of porosity by assuming that the flow in the porous matrix obeys modified Darcy's law. The stochastic MHD Reynold's type equation is derived by using the Christensen's stochastic method developed for hydrodynamic lubrication of rough surfaces. Two types of one-dimensional surface roughness (radial and azimuthal) patterns are considered.Findings– The expressions for the mean MHD squeeze-film pressure and mean load-carrying capacity are obtained numerically. The results are shown graphically for selected representative parametric values. It is found that the response time increases significantly for the MHD case as compared to the corresponding non-conducting lubricants. The effect of roughness parameter is to increase/decrease the load-carrying capacity and the response time for azimuthal/radial roughness patterns as compared to the smooth case. Also, the effect of porous parameter is to decrease the load-carrying capacity and response time as compared to the solid case.Originality/value– In this paper, an attempt has been made to analyse the combined effects of surface roughness and permeability on the MHD squeeze-film characteristics between a sphere and a plane surface.