Effects Of Fluid Inertia Forces Research Articles

Effects of magnetic force and non‐Newtonian characteristics on squeeze film bearings

AbstractIn the present article, the special effects of fluid inertia forces and magnetic field in circular squeeze film bearings greased with a time‐independent thixotropic non‐Newtonian fluid have been brought to the limelight. The pressure delivery and load carrying capacity representing the recitals of bearing have been calculated with the values of yield number, thixotropic parameter, power‐law index, Reynolds number, and Hartmann number. The squeeze film pressure and load carrying capacity are increased with the rise of yield number, power‐law index, Reynolds number, and Hartmann number whereas a reverse trend is shown with the increase of thixotropic parameter or a scalar structural parameter of materials. Based on the results obtained from the present study, the influence of thixotropic fluid enhances the pressure and load carrying capacity as compared to pseudo‐plastic, Newtonian, and dilatant fluids as lubricants.

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.

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.

Inertial MHD Couple Stress Effects on Infinitely Wide Slider Bearings

This article presents a numerical study of magnetohydrodynamic (MHD) infinitely wide plane inclined slider bearings including both fluid inertia and non-Newtonian couple stress effects. Fluid inertia forces are considered in the film fluid using a simplified form of the Navier-Stokes equations. The non-Newtonian couple stress behavior of the lubricant is described based on the microcontinuum Stokes theory. The governing equations are discretized by finite differences using a boundary layer–type equations resolution. The resulting algebraic equations are solved using the Gauss-Seidel method. It is found that the couple effects of fluid inertia forces, MHD, and non-Newtonian couple stresses provide a significant improvement in the slider bearing load capacity compared to the case of the noninertia Newtonian nonconducting lubricant. The use of conducting lubricant diminishes the negative effect of inertia forces on the friction coefficient.

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.

Inertia Effects on Inclined Slider Bearings Lubricated by a Couple Stress Fluid

This article deals with a numerical investigation of fluid inertia effects on inclined slider bearings lubricated by couple stress fluids. Convective inertial forces are considered in the film fluid. A reduced version of the Navier-Stokes equations is thus derived. The non-Newtonian couple stress behavior of the lubricant is described based on the microcontinuum Stokes theory. The governing partial differential equations are discretized by finite differences based on boundary layer–type equations. The resulting algebraic equations are solved using a Gauss-Seidel method. Compared to the case of the non-inertia Newtonian lubricant, the couple effects of fluid inertia forces and non-Newtonian couple stresses provide a significant improvement in slider bearing load capacity.

Inertia Effects in Rheodynamic Lubrication of an Externally Pressurized Thrust Bearing Using Bingham Lubricant with Sinusoidal Injection

In the present theoretical investigation, the combined effects of fluid inertia forces and sinusoidal injection of the Bingham lubricant, on the performance of an externally pressurized thrust bearing with circular geometry are studied. Using the conventional two-constant Bingham model and by adopting the method of averaging inertia terms, the reduced Navier-Stokes equations are modified and numerical solutions have been obtained for the bearing performances such as the pressure distribution and the load carrying capacity for different values of Bingham number, Reynolds number, time and amplitude. The effects of fluid inertia forces and the non-Newtonian characteristics of the Bingham lubricant on the bearing performances for different sinusoidal conditions are discussed.

Fluid inertia effects in ferrofluid squeeze film between a sphere and a plate

On the ground of the ferrohydrodynamic model proposed by Shliomis [13,14], the present study investigates the influences of fluid inertia forces on the ferrofluid squeeze film between a sphere and a plate in the presence of external magnetic fields. According to the results, the effects of fluid inertia forces enhance the load capacity and prolong the approaching time for the ferrofluid sphere–plate system. Further numerical results for the load capacity are also provided in a table for engineering applications.

Effects of fluid inertia forces on the squeeze film characteristics of conical plates—ferromagnetic fluid model

ABSTRACTOn the basis of the Shliomis ferromagnetic fluid model, this paper is mainly concerned with the influences of convective fluid inertia forces in magnetic fluid‐based conical squeeze film plates in the presence of external magnetic fields. By applying the averaged momentum principle, a lubrication equation governing the film pressure is derived. Some previous contributions can be obtained from special cases of the present studies. Comparing with the non‐inertia non‐magnetic case, better squeeze film performances are predicted for the magnetic fluid‐based conical plates operating with a larger value of the inertial parameter of fluid inertia forces, the volume concentration of ferrite particles and the strength of applied magnetic fields. Some numerical results with specific cone angles are also provided in tables for engineering applications. Copyright © 2012 John Wiley & Sons, Ltd.

Theoretical Investigation of Couple Stress Squeeze Films in a Curved Circular Geometry

A theoretical investigation of the laminar squeeze flow of a couple-stress fluid between a flat circular static disk and an axisymmetric curved circular moving disk has been carried out using modified lubrication theory and microcontinuum theory. The combined effects of fluid inertia forces, curvature of the disk and non-Newtonian couple stresses on the squeeze film behavior are investigated analytically. Each of these effects and their combinations show a significant enhancement in the squeeze film behavior, and these are studied through their effects on the squeeze film pressure and the load carrying capacity of the fluid film as a function of time. Two different forms of the gapwidth between the disks have been considered, and the results have been shown to be in good agreement with the existing literature.

Inertia effects in circular squeeze film bearing using Herschel–Bulkley lubricants

Recent engineering trends in lubrication emphasize that in order to analyze the performance of bearings adequately, it is necessary to take into account the combined effects of fluid inertia forces and non-Newtonian characteristics of lubricants. In the present work, the effects of fluid inertia forces in the circular squeeze film bearing lubricated with Herschel–Bulkley fluids with constant squeeze motion have been investigated. Herschel–Bulkley fluids are characterized by an yield value which leads to the formation of a rigid core in the flow region. The shape and extent of the core formation along the radial direction is determined numerically for various values of Herschel–Bulkley number and power-law index. The bearing performances such as pressure distribution and load capacity for different values of Herschel–Bulkley number, Reynolds number, power-law index have been computed. The effects of fluid inertia and non-Newtonian characteristics on the bearing performances have been discussed.

Combined effects of non-Newtonian rheology and fluid inertia forces on the non-linear transient behaviour in circular squeeze films

On the basis of the momentum integral method and the microcontinuum theory, the combined effects of total fluid inertia forces and non-Newtonian couple stresses on the non-linear squeeze film characteristics between parallel circular discs are presented. The squeeze-film lubrication equation is derived from the Stokes couple-stress motion equation retaining total fluid inertia terms to take into account the effects of non-Newtonian couple stresses resulting from the base oil blended with various types of additives, and the effects of local fluid inertia and convective fluid inertia. The non-linear motion equation for the squeezing disc is then numerically solved by using fourth-order Runge-Kutta method. Comparing with the Newtonian-lubricant inertialess case, the combined effects of fluid inertia forces and non-Newtonian couple stresses provide a significant increment in the response time of the squeeze film. The operating life of squeeze film discs are therefore lengthened, especially for larger couple stress parameters, Reynolds numbers and body inertia parameters. A design example is provided to facilitate the engineers assessing the extent to design the non-linear squeezing film discs considering the combined effects of total fluid inertia forces and non-Newtonian couple stresses.

Inertia Effects in a Curved Non-Newtonian Squeeze Film

Inertia Effects in a Curved Non-Newtonian Squeeze Film

Staic and Dynamic Characteristics of High-Speed, Stepped Thrust Gas-Film Bearings. Theoretical Analysis Considering Fluid Inertia Forces.

Stepped thrust gas-film bearings are widely used for high-speed rotating machinery due to their simple structure and high load-carrying capacity. In such bearings, the fluid inertia forces may play an important role under high-speed operation conditions. This paper describes the effects of fluid inertia forces on the static and dynamic characteristics of stepped gas-film bearings. In the numerical analysis, the pressure distributions in the pocket and land regions are evaluated from the generalized Reynolds equation considering the centrifugal force. The pressure values at the step are calculated by considering the conservation of mechanical energy and the continuity of fluid flow in the pocket and land regions. Moreover, the dynamic response of the bearings subjected to impulsive and sinusoidal excitations are analyzed for different values of film thickness ratios. From the numerical results. the effects of fluid inertia on the static and dynamic characteristics of high-speed, stepped thrust gas-film bearings are clarified.

The Effects of Fluid Inertia Forces on the Static Characteristics of Sector-Shaped, High-Speed Thrust Bearings in Turbulent Flow Regime

This paper describes a study on the performance characteristics of sector-shaped, high-speed thrust bearings subjected to the effects of both turbulence and fluid inertia forces. The basic lubrication equations are derived by integrating the momentum and continuity equations in the polar coordinates including the full inertia terms throughout the film thickness; and a numerical calculation technique combining the control volume integration and the Newton-Raphson linearization method is applied to solve the equations. The static characteristics such as the load carrying capacity and the pressure center are calculated for various values of pad extent angle and inner-to-outer radius ratio of a pad. The theoretical results of the load carrying capacity are compared with the experimental results. It was found that the fluid inertia forces have significant effects on the static characteristics of the bearings. Good agreement was obtained between theoretical and experimental results.

Inertia effects in rheodynamic lubrication of a squeeze film bearing

Recently, it has been emphasized that in order to analyse the performances of bearings adequately, it is necessary to take into account the combined effects of fluid inertia forces and non-newtonian characteristics of lubricants. In this research work, the effects of inertia forces in the squeeze film bearing lubricated with a Bingham fluid have been investigated. A Bingham fluid possesses a yield value, therefore the shape and extent of the core formation is determined numerically for various values of Bingham number and the flow is confined to the region between the core and the disks. Averaging the inertia terms over the film thickness and defining a modified pressure gradient, the rheodynamic lubrication equation containing the inertia terms has been analysed for velocity distributions in the two regions separating the core formation. For different values of Bingham number and squeeze Reynolds' number, the film pressure and the load capacity of the bearing have been obtained. Significant inertia effects on the load capacity of the bearing have been observed. The percentage increase in load-carrying capacity, due to inertia forces for materials with varying yield values and for different values of squeeze Reynolds' number, has been compared.

The Effects of Fluid Inertia Forces on the Dynamic Behavior of Short Journal Bearings in Superlaminar Flow Regime

The effects of fluid inertia on the dynamic behavior of oil film journal bearings are theoretically investigated. The dynamic oil film forces considering the combined effects of turbulence and fluid inertia are analytically obtained under the short bearing assumption. Based on the linearized analysis, the whirl onset velocity for a balanced rigid rotor supported horizontally in the oil film journal bearings are determined initially in the case of the length-to-diameter ratio of λ = 0.5 for Reynolds numbers of Re = 2750, 4580, and 5500. Moreover, the nonlinear equations of motion for the rotor are solved by the improved Euler’s method, and the relations between the transient journal motion and the pressure distribution corresponding to the above Reynolds numbers are examined. It is found that the fluid inertia significantly affects the dynamic behavior of turbulent journal bearings under certain operating conditions.

The Effects of Fluid Inertia Forces in Parallel Circular Squeeze Film Bearings Lubricated With Pseudo-Plastic Fluids

The effects of fluid inertia forces in parallel circular squeeze film bearings lubricated with pseudo-plastic fluids are examined theoretically. In the derivation of lubrication equation, the cubic equation obtained from the empirical flow curves for pseudo-plastic fluids is used as the relation between shear stress and shear strain rate, and the inertia term in the momentum equation is approximated by the mean value averaged across the film thickness. Numerical solutions for the film pressure of circular bearings lubricated with Newtonian and pseudo-plastic fluids under the sinusoidal squeeze motion are presented in graphical form and the effects of inertia forces on the film pressure are determined.

The Effects of Fluid Inertia Forces in Squeeze Film Bearings Lubricated with Pseudo-plastic Fluids : 2nd Report, Annular Pavallel Plates Squeeze Film Bearings

In this paper, the effects of fluid inertia forces in annular parallel plate squeeze film bearings lubricated with pseudo-plastic fluids are investigated theoretically. The cubic equation obtained from the empirical flow curves for the pseudo-plastic fluids is used as the relation between shear stress and shear strain rate. Approximating the inertia term in the momentum equation by the mean value averaged across the film thickness, a lubrication equation for calculating the film pressure of annular parallel plate squeeze film bearings is derived. Applying the lubrication equation to the annular bearings under the sinusoidal squeeze motion, the effects of inertia forces on the film pressure are examined for various nonlinear factor.

The effects of fluid inertia forces in squeeze film bearings lubricated with pseudo-plastic fluids (3rd report, Theoretical analysis in the case of a small nonlinear factor)

In this paper, theoretical analysis concerning the effects of fluid inertia forces in parallel circular squeeze film bearings lubricated with pseudo-plastic fluids is presented. Based on a first order perturbation method in a small nonlinear factor, an analytical solution is derived for the calculation of pressure distribution under sinusoidal squeezing motion, and the applicability of the solution is discussed. Results obtained from the analytical solution agree well with the numerical results for a small nonlinear factor.