On the Computation of Inertial Coefficients in Squeeze-Film Bearings

1987 ◽  
Vol 201 (2) ◽  
pp. 125-131
Author(s):  
M D Ramli ◽  
J Ellis ◽  
J B Roberts
Keyword(s):  
Differential Equation ◽  
Diameter Ratio ◽  
Fluid Film ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Film Pressure ◽  
Static Eccentricity ◽  
Computational Simplicity ◽  
Analytical Expressions ◽  
Good Agreement

Inertial coefficients for full squeeze-film bearings are evaluated theoretically using Smith's differential equation relating fluid-film pressure to journal acceleration (1). The variations of the non-dimensionalized inertial coefficients with static eccentricity ratio in the radial and transverse directions are compared with some corresponding values obtained from Reinhardt and Lund (2) and Szeri et al. (3). The results from these three methods show good agreement, especially for short bearings (that is bearings with low values of length–diameter ratio). However, Smith's approach has the advantage of computational simplicity and leads to fairly simple, asymptotic, analytical expressions for very short, and very long, bearings.

Mass Conserving Cavitation Effects in Squeeze-Film Journal Bearings Subjected to Fully Reversing Loads

2010 ◽  
Author(s):  
S. Boedo
Keyword(s):  
Large Range ◽  
Journal Bearings ◽  
Experimental Results ◽  
Fluid Film ◽  
Squeeze Film ◽  
Threshold Pressure ◽  
Film Pressure ◽  
Time Histories ◽  
Cavitation Threshold ◽  
Good Agreement

This paper presents a study of cavitation effects associated with the performance of fluid-film journal bearings subjected to fully-reversing sinusoidal loading. Employing an established mass-conserving cavitation algorithm, it is observed that periodic time histories of journal eccentricity and maximum film pressure are strongly influenced by the process of cavitation formation and collapse. Good agreement of predicted and experimental results is obtained over a large range of loads for cavitation threshold pressure values typically associated with vapor cavitation.

Magnetohydrodynamic Squeeze Film Characteristics Between Parallel Circular Plates Containing a Single Central Air Bubble in the Inertial Flow Regime

1999 ◽  
Vol 66 (4) ◽  
pp. 1021-1023 ◽  
Author(s):  
R. Usha ◽  
P. Vimala
Keyword(s):  
Magnetic Field ◽  
Differential Equation ◽  
Nonlinear Differential Equation ◽  
Bubble Radius ◽  
Fluid Film ◽  
Squeeze Film ◽  
Parallel Plates ◽  
Circular Plates ◽  
Air Bubble ◽  
Approximate Analytical Solutions

In this paper, the magnetic effects on the Newtonian squeeze film between two circular parallel plates, containing a single central air bubble of cylindrical shape are theoretically investigated. A uniform magnetic field is applied perpendicular to the circular plates, which are in sinusoidal relative motion, and fluid film inertia effects are included in the analysis. Assuming an ideal gas under isothermal condition for an air bubble, a nonlinear differential equation for the bubble radius is obtained by approximating the momentum equation governing the magnetohydrodynamic squeeze film by the mean value averaged across the film thickness. Approximate analytical solutions for the air bubble radius, pressure distribution, and squeeze film force are determined by a perturbation method for small amplitude of sinusoidal motion and are compared with the numerical solution obtained by solving the nonlinear differential equation. The combined effects of air bubble, fluid film inertia, and magnetic field on the squeeze film force are analyzed.

Numerical Study of Single Pad Externally Adjustable 120° Pad Bearing Using Fluid Structure Interaction

2021 ◽  
Author(s):  
Harishkumar Kamat ◽  
Chandrakant R. Kini ◽  
Satish B. Shenoy
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Fluid Film ◽  
Structural Deformation ◽  
Radial Clearance ◽  
Solution Technique ◽  
Eccentricity Ratio ◽  
Positive Direction ◽  
Film Pressure ◽  
Marine Propulsion

Abstract High-speed turbomachinery like turbine generators and marine propulsion systems uses special fluid film bearing called externally adjustable pad bearing due to their great advantages. The principal feature of this bearing is to alter the radial clearance and film thickness along the circumferential direction to improve the bearing performance parameters. In the present study, the effect of radial and tilt adjustment of 120° pad both in upward (or negative) and downward (or positive) direction on the bearing performance is predicted for various eccentricity ratios using the CFD technique. Later the influence of fluid film pressure on the bearing pad is examined using the FSI technique. Furthermore, the effect of eccentricity ratio on the bearing performance and also on pad structure is also analyzed using CFD coupled FSI analysis. The solution technique of the present numerical analysis is validated with the already published literature and the results are in good agreement. The numerical results suggest that for bearing with negative radial and negative tilt adjustment, bearing performance is superior compared to the other adjustments. However, the structural deformation is also significant for the negative radial and negative tilt adjustment. It is also observed that pad deformation increases with the increase in eccentricity ratio as there has been a rise in fluid film pressure.

Subharmonic, Quasi-Periodic and Chaotic Motions of a Rigid Rotor Supported by an Eccentric Squeeze Film Damper

1993 ◽  
Vol 207 (6) ◽  
pp. 383-392 ◽  
Author(s):  
J Y Zhao ◽  
E J Hahn
Keyword(s):  
Reynolds Equation ◽  
Power Spectra ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Eccentricity Ratio ◽  
Jump Phenomenon ◽  
Chaotic Motions ◽  
Squeeze Film Damper ◽  
Static Eccentricity

This paper analyses the complexity of the unbalance response possible with a simple rigid rotor supported by an eccentric squeeze film damper. The damper forces are obtained from the ‘π’ film short bearing approximation to the Reynolds equation and a fourth-order Runge-Kutta integration is used to evaluate the rotor response. Poincaré maps, rotor trajectories, bifurcation diagrams and power spectra are used to elucidate and to illustrate the diversity of the system behaviour. It is shown that for a large unbalance and static eccentricity ratio, the system can exhibit undesirable jump phenomenon and subharmonic, quasi-periodic and even chaotic motions, which limit the operating conditions at which dampers should be used.

A Numerical Model for Elastohydrodynamic Analysis of Plunger and Barrel Clearances in Fuel Injection Equipment

1994 ◽  
Vol 116 (3) ◽  
pp. 597-605 ◽  
Author(s):  
D. H. Gibson ◽  
P. J. Dionne ◽  
A. K. Singhal
Keyword(s):  
Numerical Model ◽  
Pressure Distribution ◽  
Fuel Injection ◽  
Fluid Film ◽  
Structural Deformation ◽  
Squeeze Film ◽  
Poisson Effect ◽  
Full Account ◽  
Film Pressure ◽  
Strongly Coupled

This paper describes a numerical model developed to predict the elastohydrodynamic (coupled solid-fluid) response of unit injector fuel systems. These systems consist of a concentric barrel and plunger with a small annular clearance. During operating (axial movement of the plunger), highly nonuniform pressure and clearance fields are developed which are strongly coupled with each other. The model simultaneously solves for the transient response of the fluid film pressure distribution and three different structural deformation components in a two-dimensional (axial-circumferential) domain. These structural components are the transverse bending of the plunger, radial expansion of the barrel, and radial growth of the plunger from a Poisson effect. The fluid film pressure distribution is governed by the transient Reynolds equation (i.e., lubrication theory) and the structural deformation components governed by linear elastic theory. Full account is taken of these hydrostatic, hydrodynamic, and squeeze-film forces generated in the fluid. The model has been applied to several injector designs. Results have been compared with known performance characteristics and have been found to be qualitatively accurate, in that locations of plunger/barrel contact, and potential for failure, have been accurately predicted.

Squeeze Film Characteristics Between Parallel Circular Plates Containing a Single Central Air Bubble in the Inertial Flow Regime

1995 ◽  
Vol 117 (3) ◽  
pp. 513-518 ◽  
Author(s):  
H. Hashimoto
Keyword(s):  
Differential Equation ◽  
Nonlinear Differential Equation ◽  
Bubble Radius ◽  
Isothermal Condition ◽  
Fluid Film ◽  
Squeeze Film ◽  
Cylindrical Shape ◽  
Parallel Plates ◽  
Air Bubble ◽  
Film Characteristics

In this paper, the effects of an air bubble on the Newtonian squeeze film characteristics between two circular parallel plates with sinusoidal relative motion are theoretically investigated by considering the fluid film inertia effects. In the derivation of the lubrication equation, a single central air bubble of a cylindrical shape is considered. Approximating the momentum equation governing the squeeze film flow by the mean value averaged across the film thickness and assuming an ideal gas under isothermal condition for an air bubble, a nonlinear differential equation for the bubble radius is obtained. The nonlinear differential equation is solved by the Runge-Kutta-Gill method, and then the squeeze film force is determined. Moreover, the analytical solutions for the air bubble radius and pressure distribution are derived based on the perturbation method for a small amplitude of sinusoidal motion, and the analytical results are compared with the numerical results. From the calculated results, the combined effects of air bubble and fluid film inertia on the squeeze film force are clarified.

PURE SQUEEZE FILM BEHAVIOR OF LONG JOURNAL BEARINGS WITH COUPLE STRESS FLUIDS UNDER DYNAMIC LOADING

2000 ◽  
Vol 24 (3-4) ◽  
pp. 477-492 ◽  
Author(s):  
Jaw-Ren Lin ◽  
Yeon-Pun ◽  
Yuan Kang ◽  
Kuo-Chiang Cha
Keyword(s):  
Couple Stress ◽  
Reynolds Equation ◽  
Stokes Equations ◽  
Equations Of Motion ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Film Pressure ◽  
Couple Stresses ◽  
Bearing Life

On the basis of microcontinuum theory, a theoretical analysis of pure squeeze film behavior of journal bearings with couple stress lubricants operating under a dynamic load is presented. To account for the effects of couple stresses arising from the lubricant blended with various additives, the modified Reynolds equation governing the film pressure is obtained from Stokes equations of motion. Various bearing characteristics for long bearings are then calculated. According to the results obtained, the influence of couple stresses on the dynamic squeeze film motion is apparent and not negligible. Comparing with the Newtonian-lubricant case, the effects of coupe stresses provide and enhancement in the film pressure as well as a reduction in the velocity of the journal center; consequently, the maximum eccentricity ratio of the journal center is decreased. On the whole, the bearing lubricated with couple stress fluid signifies and improvement in the dynamic squeeze film performance and results in longer bearing life.

Fluid Inertia Forces in Squeeze Film Dampers

1991 ◽  
Author(s):  
A. El-Shafei ◽  
S. M. Crandall
Keyword(s):  
Reynolds Number ◽  
Velocity Profiles ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Eccentricity Ratio ◽  
Number Range ◽  
Squeeze Film Dampers ◽  
Energy Approximation ◽  
Inertia Forces ◽  
Good Agreement

Abstract Fluid inertia forces in Squeeze Film Dampers (SFDs) are obtained for short and long dampers using an energy approximation based on the assumption that the velocity profiles with inertia are the same as those for an inertialess fluid. It is shown that the inertia forces thus obtained are proportional to the usual radial, centripetal, tangential and Coriolis accelerations of the journal, plus an additional nonlinear acceleration. The inertia coefficients of the dampers are obtained, for both uncavitated and cavitated dampers, and are plotted versus the eccentricity ratio for centered, nearly circular whirl. The inertia forces obtained by the energy approximation are compared to an exact linearized solution for centered, circular whirl, and good agreement is found for both short and long dampers in the Reynolds number range of ordinary SFD application.

Analysis of ‘Boosted Lubrication’ in Human Joints

1970 ◽  
Vol 12 (5) ◽  
pp. 364-369 ◽  
Author(s):  
D. Dowson ◽  
A. Unsworth ◽  
V. Wright
Keyword(s):  
Synovial Fluid ◽  
Operating Conditions ◽  
Fluid Film ◽  
Squeeze Film ◽  
Cartilage Surface ◽  
Human Joints ◽  
Experimental Findings ◽  
Joint Behaviour ◽  
Human Joint ◽  
Good Agreement

The load-bearing human joint is a self-acting dynamically loaded bearing which employs a porous and elastic bearing material (articular cartilage) and a highly non-Newtonian lubricant (synovial fluid). The authors' understanding is that the human joint experiences fluid-film (including elastohydrodynamic), mixed and boundary lubrication in its various operating conditions. It has been recognized that squeeze-film action is capable of providing considerable protection to the cartilage surface once a fluid film is generated (6) (8)§. Furthermore, the possibility of an increasing concentration of hyaluronic acid in synovial fluid during the squeeze-film action due to the porous nature of the cartilage and its surface topography and the known relationship between this concentration and the effective viscosity (7) has led to the concept of ‘boosted lubrication’ as an important feature of joint behaviour (10). A mathematical analysis of the concept of boosted lubrication of human joints is presented in this paper. The predictions of the analysis are shown to be in good agreement with experimental findings (12).

Influence of different flow regimes on the performance characteristics of a four-pad hydrostatic squeeze film damper loaded between pads

2019 ◽  
Vol 71 (3) ◽  
pp. 440-446
Author(s):  
Amina Nemchi ◽  
Ahmed Bouzidane ◽  
Aboubakeur Benariba ◽  
Hicham Aboshighiba
Keyword(s):  
Turbulent Flow ◽  
Load Capacity ◽  
Flow Regimes ◽  
Performance Characteristics ◽  
Squeeze Film ◽  
Eccentricity Ratio ◽  
Flow Conditions ◽  
Content Type ◽  
Turbulent Flow Regime ◽  
Squeeze Film Dampers

Purpose The purpose of this paper is to study the influence of different flow regimes on the dynamic characteristics of four-pad hydrostatic squeeze film dampers (SFDs) loaded between pads. Design/methodology/approach A numerical model based on Constantinescu’s turbulent lubrication theory using the finite difference method has been developed and presented to study the effect of eccentricity ratio on the performance characteristics of four-pad hydrostatic SFDs under different flow regimes. Findings It was found that the influence of turbulent flow on the dimensionless damping of four-pad hydrostatic SFDs appears to be essentially controlled by the eccentricity ratio. It was also found that the laminar flow presents higher values of load capacity compared to bearings operating under turbulent flow conditions. Originality/value In fact, the results obtained show that the journal bearing performances are significantly influenced by the turbulent flow regime. The study is expected to be useful to bearing designers.

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