The Gaseous Squeeze-Film at Moderately Large Squeeze Numbers

1970 ◽  
Vol 92 (4) ◽  
pp. 766-781 ◽  
Author(s):  
C. H. T. Pan
Keyword(s):  
Edge Effects ◽  
Lubrication Theory ◽  
Point Of View ◽  
Squeeze Film ◽  
Universal Functions ◽  
Inertia Effects ◽  
Gas Lubrication ◽  
Spherical Bearing ◽  
Squeeze Number ◽  
Isothermal Gas

The asymptotic analysis of the gaseous squeeze-film bearing has been extended to obtain 0 {σ−1/2} effects in accordance with the isothermal gas lubrication theory and the method of singular perturbation. 0 {σ−1/2} corrections are identified to contain not only edge effects (inner problem) but also edge-interior interactions which are analogous to the boundary layer displacement effects in aerodynamics. The latter features can further be recognized to be related to mean-gap taper, squeeze taper, and cross-edge sliding. These results are discussed from the point of view of “global bearing properties” including the temporal mean as well as the in-phase and quadrature synchronous components of the fluid film force and moment. The edge effects are presented in terms of universal functions which can be used directly as corrections in the global properties. The edge-interior interactions must be determined by solving the asymptotic p.d.e. with boundary condition also expressed in terms of universal functions. Formulations applicable to cylindrical, conical, and spherical bearing geometries are outlined. Illustrative numerical examples are provided. Conditions affecting the validity of the isothermal gas lubrication theory (neglecting inertia effects) as related to the magnitude of the squeeze number are discussed.

Squeeze Film Flow Between Arbitrary Two-Dimensional Surfaces Subject to Normal Oscillations

1978 ◽  
Vol 100 (3) ◽  
pp. 316-322 ◽  
Author(s):  
J. A. Tichy ◽  
M. F. Modest
Keyword(s):  
Thrust Bearing ◽  
Analytic Solution ◽  
Film Flow ◽  
Oscillation Amplitude ◽  
Reynolds Numbers ◽  
Lubrication Theory ◽  
Squeeze Film ◽  
Two Dimensional ◽  
Surface Geometry ◽  
Inertia Effects

An analytic solution is presented for squeeze film flow with smooth, arbitrary, two-dimensional surface geometry. One surface undergoes sinusoidal oscillation toward the other. The oscillation amplitude is much smaller than the film thickness, which is in turn much smaller than the bearing length. The solution improves on the lubrication theory due to the inclusion of inertia effects. The solution to an illustrative problem is presented—the thrust bearing. The velocity field, pressure distribution and load differ significantly from those predicted by lubrication theory. The results show the lubrication solution for load and pressure to be in error by over 100 percent for Reynolds numbers as low as 5.

Inertia Effects on Compressible Squeeze Films

1995 ◽  
Vol 117 (1) ◽  
pp. 94-102 ◽  
Author(s):  
Jongmin Kang ◽  
Zhaoshun Xu ◽  
Adnan Akay
Keyword(s):  
Numerical Solutions ◽  
Fluid Layer ◽  
Phase Changes ◽  
Experimental Results ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Bearing Force ◽  
The Mean ◽  
Squeeze Number

In this paper, the combined effects of compressibility and fluid inertia in a squeeze film are considered. The governing equations are derived using an integral method for a one-dimensional case, initially considering a combination of Couette and Poiseuille Flows. Numerical and experimental results are obtained for the case of a pure squeeze film between flat circular disks. Influence of the film geometry was examined by considering a cavity on the surface of one of the disks. The numerical solutions are obtained by use of the Crank-Nicholson method with Lax modification. Comparison of the numerical results for pressure in the film with the experimental results show good agreement. The inertia of the fluid is found to significantly influence the pressure waveform in the film by altering the phase of the pressure developed in the film with respect to the oscillating disk. It is shown that these phase changes lead to “resonances” in the mean bearing force. The results also show that the mean bearing force can be superambient or subambient depending on the squeeze number. Both the damping and the bearing force show a “jump” at a critical squeeze number. Damping due to the fluid layer is shown to be amplitude-dependent.

Investigation of the Squeeze Film Dynamics Underneath a Microstructure With Large Oscillation Amplitudes and Inertia Effects

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Nadim A. Diab ◽  
Issam A. Lakkis
Keyword(s):  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Squeeze Film ◽  
Dsmc Method ◽  
Inertia Effects ◽  
Flow Parameters ◽  
Fluid Behavior ◽  
Dimensionless Groups ◽  
Simulation Monte Carlo ◽  
The Impact

This paper presents direct simulation Monte Carlo (DSMC) numerical investigation of the dynamic behavior of a gas film in a microbeam. The microbeam undergoes large amplitude harmonic motion between its equilibrium position and the fixed substrate underneath. Unlike previous work in literature, the beam undergoes large displacements throughout the film gap thickness and the behavior of the gas film along with its impact on the moving microstructure (force exerted by gas on the beam's front and back faces) is discussed. Since the gas film thickness is of the order of few microns (i.e., 0.01 < Kn < 1), the rarefied gas exists in the noncontinuum regime and, as such, the DSMC method is used to simulate the fluid behavior. The impact of the squeeze film on the beam is investigated over a range of frequencies and velocity amplitudes, corresponding to ranges of dimensionless flow parameters such as the Reynolds, Strouhal, and Mach numbers on the gas film behavior. Moreover, the behavior of compressibility pressure waves as a function of these dimensionless groups is discussed for different simulation case studies.

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical CO2 Expander

2017 ◽  
Author(s):  
Bugra Ertas ◽  
Adolfo Delgado ◽  
Jeffrey Moore
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Mechanical Impedance ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Damping Behavior ◽  
Impedance Testing ◽  
Stiffness And Damping ◽  
Onset Of Cavitation

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping; the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

scholarly journals Squeeze-Film Damper Technology: Part 1 — Prediction of Finite Length Damper Performance

1983 ◽  
Author(s):  
J. W. Lund ◽  
A. J. Smalley ◽  
J. A. Tecza ◽  
J. F. Walton
Keyword(s):  
Finite Length ◽  
Gas Turbines ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Strongly Coupled ◽  
Squeeze Film Damper ◽  
Rotor Systems ◽  
Squeeze Film Dampers ◽  
Calculation Results

Squeeze-film dampers are commonly used in gas turbine engines and have been applied successfully in a great many new designs, and also as retrofits to older engines. Of the mechanical components in gas turbines, squeeze-film dampers are the least understood. Their behavior is nonlinear and strongly coupled to the dynamics of the rotor systems on which they are installed. The design of these dampers is still largely empirical, although they have been the subject of a large number of past investigations. To describe recent analytical and experimental work in squeeze-film damper technology, two papers are planned. This abstract outlines the first paper, Part 1, which concerns itself with squeeze-film damper analysis. This paper will describe an analysis method and boundary conditions which have been developed recently for modelling dampers, and in particular, will cover the treatment of finite length, feed and drain holes and fluid inertia effects, the latter having been shown recently to be of great importance in predicting rotor system behavior. A computer program that solves the Reynolds equation for the above conditions will be described and sample calculation results presented.

Squeeze Film Flow in Arbitrarily Shaped Journal Bearings Subject to Oscillations

1978 ◽  
Vol 100 (3) ◽  
pp. 323-329 ◽  
Author(s):  
M. F. Modest ◽  
J. A. Tichy
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Film Flow ◽  
Linear Partial Differential Equation ◽  
Journal Bearings ◽  
Lubrication Theory ◽  
Squeeze Film ◽  
Solution Technique ◽  
Practical Applications ◽  
High Reynolds

Squeeze film flow in smooth but arbitrarily shaped infinite journal bearings is considered. The nonrotating shaft is subject to small sinusoidal oscillations. An analytic solution is presented which improves on the lubrication theory by including inertia terms in the equations of motion. The solution technique is to introduce a stream function by which the problem can be reduced to a linear partial differential equation, with time varying boundary conditions, which can be solved by conventional means. The solution to an illustrative problem is presented—the circular journal and bearing. The velocity field and pressure distribution differ qualitatively from those predicted by lubrication theory due to the existence of out-of-phase components. The results show that the lubrication solution for the amplitude of load and pressure can be significantly in error for high Reynolds number operation of a bearing at low eccentricity ratio. At high eccentricity ratios, however, the lubrication theory can be used with confidence, even at very extreme (high Reynolds number) conditions. Simple approximate closed form expressions for pressure and load are presented which are sufficiently accurate for engineering use (error <3 percent) in the range of practical applications.

Fluid Inertia Effects in a Non-Newtonian Squeeze Film Between Two Plane Annuli

1999 ◽  
Vol 122 (4) ◽  
pp. 872-875 ◽  
Author(s):  
R. Usha and ◽  
P. Vimala
Keyword(s):  
Carrying Capacity ◽  
Integral Method ◽  
Squeeze Flow ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Load Carrying ◽  
Analytical Expressions ◽  
Plastic Fluids

An analysis is presented for the laminar squeeze flow of an incompressible powerlaw fluid between parallel plane annuli using the modified lubrication theory and energy integral method. The local and the convective inertia of the flow are considered in the investigation. Analytical expressions for the load carrying capacity of the squeeze film are obtained using both the methods and are compared with those based on the assumption of inertialess flow. It is observed that the inertia correction in the load carrying capacity is more significant for pseudo-plastic fluids, n<1.[S0742-4787(00)00504-X]

Theoretical Investigation of Unsteady Squeeze Flow in a Curved Newtonian Squeeze Film

2002 ◽  
Vol 124 (4) ◽  
pp. 865-869 ◽  
Author(s):  
R. Usha and ◽  
P. Vimala
Keyword(s):  
Arbitrary Shape ◽  
Normal Force ◽  
Viscous Incompressible Fluid ◽  
Circular Disk ◽  
Squeeze Flow ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Inertia Effects ◽  
Curvature Effects ◽  
Load Carrying

The laminar squeeze flow of a viscous incompressible fluid between a flat circular disk and an axisymmetric curved disk of arbitrary shape is investigated theoretically using modified lubrication theory. The characteristics of squeeze film are investigated through inertia and curvature effects on the normal force exerted on the upper curved moving disk described by an exponential function for the sinusoidal squeeze motion. The constant force squeezing state is also examined. It has been observed that the load carrying capacity of the curved squeeze film is strongly influenced by the curvature and inertia effects.

Inertia Effects in Squeeze-Film Damper Bearings Generated by Circumferential Oil Supply Groove

2001 ◽  
Author(s):  
Jørgen W. Lund ◽  
Claus M. Myllerup ◽  
Henning Hartmann
Keyword(s):  
Dynamic Properties ◽  
Bulk Flow ◽  
Squeeze Film ◽  
Perturbation Approach ◽  
Inertia Effects ◽  
Squeeze Film Damper ◽  
Oil Supply ◽  
Reaction Forces ◽  
Flow Approximation ◽  
Acceleration Term

Abstract The dynamic properties of an industrial Squeeze-Film Damper (SFD) bearing design are described using the well-known perturbation approach, where the reaction forces induced by small movements away from the position of equilibrium are expanded into a Taylor series in terms of displacement, velocity, and acceleration. Although generally negligible, the acceleration term can become significant in SFD bearings when inertia effects in the damper lands are enhanced by the flow in a central circumferential oil supply groove. By using a bulk flow approximation in the oil supply groove an explicit expression is derived for the acceleration term. Experimental results confirm the significance of the oil supply groove geometry and appear to validate the bulk flow approximation.

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