Flow in Finite-Width Thrust Bearings Including Inertial Effects: II—Turbulent Flow

1978 ◽  
Vol 100 (3) ◽  
pp. 339-345 ◽  
Author(s):  
B. E. Launder ◽  
M. A. Leschziner
Keyword(s):  
Turbulent Viscosity ◽  
Turbulence Energy ◽  
Finite Width ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Thrust Bearings ◽  
Inertial Flow ◽  
Transport Effects ◽  
Rate Of Dissipation ◽  
Selection Of

A new set of turbulent resistance laws for hydrodynamic lubricant films has been derived with the aid of a turbulence model which includes transport effects on two turbulence parameters. The model consists of two differential equations for the turbulence energy and its rate of dissipation and a constitutive equation for the turbulent viscosity. The model places no restrictions on the Reynolds number. An efficient finite-difference scheme, based on the integro-differential approach and incorporating the resistance laws and a set of accurate inertial coefficients, is applied to the solution of the turbulent inertial flow in finite-width slider bearings. A selection of predictions is presented for non-inertial and inertial flows. The former are compared with solutions obtained with alternative turbulent lubrication theories. The importance of including fluid inertia effects is demonstrated.

Fluid-Inertia Effects in Spherical Hydrostatic Thrust Bearings

1967 ◽  
Vol 10 (3) ◽  
pp. 316-324 ◽  
Author(s):  
D. Dowson ◽  
C. M. Taylor
Keyword(s):  
Fluid Inertia ◽  
Inertia Effects ◽  
Thrust Bearings

Flow in Finite-Width, Thrust Bearings Including Inertial Effects: I—Laminar Flow

1978 ◽  
Vol 100 (3) ◽  
pp. 330-338 ◽  
Author(s):  
B. E. Launder ◽  
M. Leschziner
Keyword(s):  
Laminar Flow ◽  
Numerical Procedure ◽  
Solution Procedure ◽  
Finite Width ◽  
Inertial Effects ◽  
Full Inclusion ◽  
Thrust Bearings ◽  
Flow Problems ◽  
Differential Approach ◽  
Inertial Flow

Presented is a new numerical procedure for the calculation of flow in finite-width bearing films. The method, based on the integro-differential approach, is a development of schemes devised by Patankar and Spalding [8] and Gosman and Pun [9] for general flows occurring in fields other than tribology. Principal features of the method are: the full inclusion of inertial effects; the retention of “primitive” variables; the use of a marching solution procedure using line-by-line solution of the discretized conservation equations. Applications to several aspects of laminar inertial flow problems are discussed.

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.

Annular Squeeze Films With Inertial Effects

1983 ◽  
Vol 105 (3) ◽  
pp. 361-363 ◽  
Author(s):  
S. R. Turns
Keyword(s):  
Annular Plate ◽  
Equation Of Motion ◽  
Plate Motion ◽  
Squeezing Flow ◽  
Approximation Technique ◽  
Inertial Effects ◽  
Fluid Inertia ◽  
Governing Equations ◽  
Inertia Effects ◽  
Incompressible Newtonian Fluid

An analysis of the laminar squeezing flow of an incompressible Newtonian fluid between parallel plane annuli is presented in which a successive approximation technique is used to account for fluid inertia effects. An expression for the force generated by the fluid is developed and coupled to the equation of motion for the annular plate. Results are presented from the numerical integration of the governing equations for the plate motion.

A Comparison of Algebraic and Differential Second-Moment Closures for Axisymmetric Turbulent Shear Flows With and Without Swirl

1988 ◽  
Vol 110 (2) ◽  
pp. 216-221 ◽  
Author(s):  
S. Fu ◽  
P. G. Huang ◽  
B. E. Launder ◽  
M. A. Leschziner
Keyword(s):  
Shear Flows ◽  
Turbulent Jets ◽  
Moment Closure ◽  
Turbulent Shear ◽  
Turbulence Energy ◽  
Second Moment ◽  
Second Moment Closure ◽  
Transport Effects ◽  
Related Stress ◽  
Comparison Of The Results

Computations are reported for three axisymmetric turbulent jets, two of which are swirling and one containing swirl-induced recirculation, obtained with two models of turbulence: a differential second-moment (DSM) closure and an algebraic derivative thereof (ASM). The models are identical in respect of all turbulent processes except that, in the ASM scheme, stress transport is represented algebraically in terms of the transport of turbulence energy. The comparison of the results thus provides a direct test of how well the model of stress transport adopted in ASM schemes simulates that of the full second-moment closure. The comparison indicates that the ASM hypothesis seriously misrepresents the diffusive transport of the shear stress in nonswirling axisymmetric flows, while in the presence of swirl the defects extend to all stress components and are aggravated by a failure to account for influential (additive) swirl-related stress-transport terms in the algebraic modelling process. The principal conclusion thus drawn is that in free shear flows where transport effects are significant, it is advisable to adopt a full second-moment closure if turbulence modelling needs to proceed beyond the eddy-viscosity level.

Extended Finite Element Analysis of Journal Bearing Dynamic Forced Performance to Include Fluid Inertia Force Coefficients

2012 ◽  
Author(s):  
Luis San Andrés
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Small Amplitude ◽  
Forced Response ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Force Coefficients ◽  
Reaction Forces ◽  
Bearing Stiffness

Reynolds equation governs the generation of hydrodynamic pressure in oil lubricated fluid film bearings. The static and dynamic forced response of a bearing is obtained from integration of the film pressure on the bearing surface. For small amplitude journal motions, a linear analysis represents the fluid film bearing reaction forces as proportional to the journal center displacements and velocity components through four stiffness and four damping coefficients. These force coefficients are integrated into rotor-bearing system structural analysis for prediction of the system stability and the synchronous response to imbalance. Fluid inertia force coefficients, those relating reaction forces to journal center accelerations, are routinely ignored because most oil lubricated bearings operate at relatively low Reynolds numbers, i.e., under slow flow conditions. Modern rotating machinery operates at ever increasing surface speeds to deliver more power in smaller size units. Under these operating conditions fluid inertia effects need to be accounted for in the forced response of oil lubricated bearings, as recent experimental test data also reveal. The paper presents a finite element formulation to predict added mass coefficients in oil lubricated bearings by extending a basic formulation that already calculates the bearing stiffness and damping force coefficients. That is, a small amplitude perturbation analysis of the lubrication flow equations keeps the temporal fluid inertia effects and develops a set of equations to obtain the bearing stiffness, damping and inertia force coefficients. The method does not impose on the cost of the original formulation which makes it very attractive for ready implementation in existing software. Predictions of the computational model are benchmarked against archival test data for an oil-lubricated pressure dam bearing supporting large compressors. The comparisons show fluid inertia effects cannot be ignored for operation at high rotor speeds and with small static loads.

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