Experimental Evaluation of Sector-Shaped Hydrodynamic Thrust Bearings Under Translation and Transverse Vibration

1994 ◽  
Vol 116 (3) ◽  
pp. 521-527 ◽  
Author(s):  
Y. K. Wang ◽  
C. D. Mote
Keyword(s):  
Reynolds Number ◽  
Transverse Vibration ◽  
Thrust Bearing ◽  
Lubrication Theory ◽  
Fluid Inertia ◽  
Thrust Bearings ◽  
Spring Force ◽  
Bearing Load ◽  
The Mean ◽  
Simultaneous Translation

The bearing load of a plane inclined sector-shaped hydrodynamic thrust bearing, under simultaneous translation and transverse vibration, is measured experimentally. The results are used to evaluate the lubrication theory solutions. Consequently, both the influences of the unsteady film inertia, measured by the squeeze Reynolds number Res, and the convective film inertia, measured by the modified Reynolds number Re*, on load amplitude and phase are investigated. It is found that the inertia-neglected lubrication solutions underestimate: (1) the oscillatory component of the bearing load by 6.5 percent at Res = 1.0 and by 1.4 percent at Re* = 1.0, and (2) the mean component of the bearing load by 0.7 percent at Res = 1.0 and by 2.0 percent at Re* = 1.0 Moreover, the fluid inertia induces an equivalent negative spring force component which shifts the phase of the bearing load by 9.5 deg at Res =1.0 and by 4 deg at Re* = 1.0 as compared to the lubrication theory predictions. Hence it can be an important consideration when designing bearings for vibration control purposes.

The Effect of Lubricant Inertia Near the Leading Edge of a Plane Slider Bearing

1987 ◽  
Vol 109 (1) ◽  
pp. 60-64 ◽  
Author(s):  
R. H. Buckholz
Keyword(s):  
Reynolds Number ◽  
Leading Edge ◽  
Lubrication Theory ◽  
Major Conclusion ◽  
Fluid Inertia ◽  
Slider Bearing ◽  
Flux Balance ◽  
Analytical Results ◽  
Pressure Boundary Condition ◽  
Flow Through

The influence of fluid inertia on a plane slider bearing that operates at a 0(1) modified Reynolds number is examined in this study. The flow is laminar, and the Reynolds number—based on the slider velocity, lubricant kinematic viscosity, and leading-edge slider height—can be as high as 1000. Our major conclusion is that the primary effect of fluid inertia is to raise the pressure boundary condition near the bearing leading-edge. Lubrication theory is used to determine the pressure in the fluid film in the region downstream of the bearing entry. The leading-edge pressure increase caused by convective inertia is determined by a mass-flux balance between the flow near the leading-edge, and the flow through the bearing gap, which is determined by lubrication theory. Analytical results are obtained both for the convective-inertia pressure at the bearing entrance and for the pressure under the slider bearing. Results are compared to other numerical calculations and to analytical results, where the fluid inertia terms were kept throughout the bearing gap.

Magnetohydrodynamic lubrication flow between parallel plates

1966 ◽  
Vol 26 (3) ◽  
pp. 537-543 ◽  
Author(s):  
E. Roland Maki ◽  
Dennis C. Kuzma ◽  
Russell J. Donnelly
Keyword(s):  
Thrust Bearing ◽  
Lubrication Theory ◽  
Parallel Plates ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Theory And Experiment ◽  
Good Agreement

The magnetohydrodynamic lubrication flow in an externally pressurized thrust bearing is investigated both theoretically and experimentally. The ordinary magnetohydrodynamic lubrication theory for this bearing is extended to include fluid inertia effects. Very good agreement is obtained between theory and experiment.

Inertial contributions to friction measurements in thrust bearings

2021 ◽  
pp. 135065012110653
Author(s):  
Jonathon K. Schuh
Keyword(s):  
Scaling Laws ◽  
Thrust Bearing ◽  
Friction Reduction ◽  
Textured Surface ◽  
Fluid Inertia ◽  
Viscous Effects ◽  
Navier Stokes Equation ◽  
Moving Plate ◽  
Thrust Bearings ◽  
Lubricated Sliding

Surface textures decrease friction in lubricated sliding contact. Traditionally, the friction reduction for a given textured surface is determined by using the Reynolds equation, which neglects fluid inertia. However, as the separation and relative motion between the surfaces increase, inertia can affect the measured tangential and normal forces for flow over a textured surface, and thus cause the coefficient of friction to differ from the purely viscous, Stokes flow prediction. Here, the increase in torque and normal force between a moving plate and stationary textured surface, which simulates a textured thrust bearing, are calculated as a function of the Reynolds number in the thin film limit. The predictions for a non-textured thrust bearing are compared to fully 3-D numerical simulations of the incompressible Navier-Stokes equation, and the predictions for textured thrust bearings are compared to experimental data given in the literature. Good agreement is seen between the predictions and the data, validating the predicted scaling laws. This work also suggests that inertia can be used as a secondary effect to reduce friction in lubricated sliding, and textures that take advantage of the inertial effects will have lower friction than textures that only use purely viscous effects.

Approximations in Hydrodynamic Lubrication

1992 ◽  
Vol 114 (1) ◽  
pp. 14-25 ◽  
Author(s):  
R. X. Dai ◽  
Q. Dong ◽  
A. Z. Szeri
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Hydrodynamic Lubrication ◽  
Lubrication Theory ◽  
Navier Stokes ◽  
Fluid Inertia ◽  
Navier Stokes Equations ◽  
Number Range ◽  
Bearing Stiffness

In this numerical study of the approximations that led Reynolds to the formulation of classical Lubrication Theory, we compare results from (1) the full Navier-Stokes equations, (2) a lubrication theory relative to the “natural,” i.e., bipolar, coordinate system of the geometry that neglects fluid inertia, and (3) the classical Reynolds Lubrication Theory that neglects both fluid inertia and film curvature. By applying parametric continuation techniques, we then estimate the Reynolds number range of validity of the laminar flow assumption of classical theory. The study demonstrates that both the Navier-Stokes and the “bipolar lubrication” solutions converge monotonically to results from classical Lubrication Theory, one from below and the other from above. Furthermore the oil-film force is shown to be invariant with Reynolds number in the range 0 < R < Rc for conventional journal bearing geometry, where Rc is the critical value of the Reynolds number at first bifurcation. A similar conclusion also holds for the off-diagonal components of the bearing stiffness matrix, while the diagonal components are linear in the Reynolds number, in accordance with the small perturbation theory of DiPrima and Stuart.

On Parallel Hybrid Guide Bearings Under Combined Sliding and Small Amplitude Vibration

1994 ◽  
Vol 116 (1) ◽  
pp. 127-132 ◽  
Author(s):  
S. H. Chen ◽  
C. D. Mote
Keyword(s):  
Small Amplitude ◽  
Squeeze Film ◽  
Phase Lag ◽  
Fluid Inertia ◽  
Parallel Hybrid ◽  
Bearing Load ◽  
Hybrid Bearing ◽  
Unsteady Fluid ◽  
Saw Blade ◽  
Simultaneous Translation

An original hybrid bearing model, operating under constant volumetric incompressible lubricant supply rate Q*, is proposed for 2-D parallel hybrid guide bearings subject to simultaneous translation and small amplitude transverse vibration. The model may describe the typical fluid film constrained between a translating/rotating saw blade and a saw guide, where lubricant is fed directly into the oscillating film. The inner boundary, or recess, pressure is time varying and coupled to the external lubricant supply. Unsteady fluid inertia resulting from vibration is measured by the squeeze Reynolds’ number Res and modeled. A methodology for analytical solution is developed to predict the amplitude and phase of the dynamic bearing load Wt*. A sample hybrid bearing, used to demonstrate the film pressure generating mechanisms in hybrid squeeze film, generates a 1.1 to 7.1 percent larger Wt* with a 5 to 21 deg phase lag for 1 ≤ Q* ≤ 4 when compared to Wt* produced in a hydrodynamic squeeze film bearing at the same Res. This phase shift can be significant when bearings are used for vibration control purposes.

Plane Slider Bearing Load Due to Fluid Inertia—Experiment and Theory

1985 ◽  
Vol 107 (1) ◽  
pp. 32-38 ◽  
Author(s):  
J. A. Tichy ◽  
S.-H. Chen
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Pressure Jump ◽  
Experimental Measurements ◽  
Small Reynolds Number ◽  
Inertia Effect ◽  
Fluid Inertia ◽  
Slider Bearing ◽  
Bearing Load ◽  
Slow Velocity

Experimental measurements of load in a simulated plane slider bearing have been performed. The flow is laminar but modified Reynolds numbers up to 30 are obtained. In comparison with actual bearings, large film thickness and slow velocity are used to avoid experimental difficulties and isolate the inertia effect. The load is found to have increased by 100 percent relative to lubrication theory at modified Reynolds number about ten. Most existing inertia theories predict only a small effect at this Reynolds number. A simple theory is proposed to account for this discrepancy, combining existing models which have considered an inlet pressure jump and small Reynolds number perturbation analysis.

Optimum Stiffness of Externally Pressurized Thrust Bearings in Turbulent Regime

1970 ◽  
Vol 92 (3) ◽  
pp. 457-465 ◽  
Author(s):  
F. A. Shen
Keyword(s):  
Reynolds Number ◽  
Thrust Bearing ◽  
Reynolds Numbers ◽  
Turbulent Regime ◽  
Constant Flow ◽  
Thrust Bearings ◽  
High Reynolds Numbers ◽  
Study Results ◽  
Bearing Design ◽  
High Reynolds

The requirements for the optimum stiffness and the corresponding stiffness values of several types of externally pressurized, incompressible fluid-film thrust bearings under a turbulent Couette flow condition have been established. Study results indicate that the dimensionless optimum stiffness of the thrust bearing using any of the several types of geometrically restrictive compensators such as capillary and orifice, decreases with increasing Reynolds number. At high Reynolds numbers, the effect of varying Reynolds number on the stiffness becomes quite small. In contrast to the aforementioned restrictive compensation, the dimensionless stiffness of a constant-flow bearing design increases strongly with increasing Reynolds number. At Reynolds number of 106, the dimensionless stiffness varies approximately according to Re0.8.

The flow of liquid in a stream from the standard turbine impeller

1979 ◽  
Vol 44 (3) ◽  
pp. 700-710 ◽  
Author(s):  
Ivan Fořt ◽  
Hans-Otto Möckel ◽  
Jan Drbohlav ◽  
Miroslav Hrach
Keyword(s):  
Reynolds Number ◽  
Kinematic Viscosity ◽  
Momentum Flux ◽  
Relative Size ◽  
Mean Velocity ◽  
Axial Profile ◽  
The Mean ◽  
Hot Film ◽  
Turbine Impeller

Profiles of the mean velocity have been analyzed in the stream streaking from the region of rotating standard six-blade disc turbine impeller. The profiles were obtained experimentally using a hot film thermoanemometer probe. The results of the analysis is the determination of the effect of relative size of the impeller and vessel and the kinematic viscosity of the charge on three parameters of the axial profile of the mean velocity in the examined stream. No significant change of the parameter of width of the examined stream and the momentum flux in the stream has been found in the range of parameters d/D ##m <0.25; 0.50> and the Reynolds number for mixing ReM ##m <2.90 . 101; 1 . 105>. However, a significant influence has been found of ReM (at negligible effect of d/D) on the size of the hypothetical source of motion - the radius of the tangential cylindrical jet - a. The proposed phenomenological model of the turbulent stream in region of turbine impeller has been found adequate for values of ReM exceeding 1.0 . 103.

scholarly journals Settling of an asymmetric dumbbell in a quiescent fluid

2016 ◽  
Vol 802 ◽  
pp. 174-185 ◽  
Author(s):  
F. Candelier ◽  
B. Mehlig
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Size Difference ◽  
Fluid Inertia ◽  
Horizontal Orientation ◽  
Vertically Aligned ◽  
Rigid Rod ◽  
Quiescent Fluid

We compute the hydrodynamic torque on a dumbbell (two spheres linked by a massless rigid rod) settling in a quiescent fluid at small but finite Reynolds number. The spheres have the same mass densities but different sizes. When the sizes are quite different, the dumbbell settles vertically, aligned with the direction of gravity, the largest sphere first. But when the size difference is sufficiently small, then its steady-state angle is determined by a competition between the size difference and the Reynolds number. When the sizes of the spheres are exactly equal, then fluid inertia causes the dumbbell to settle in a horizontal orientation.

scholarly journals Aerodynamics of smooth and rough square-section prisms at incidence in very high Reynolds-number cross-flows

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Nils Paul van Hinsberg
Keyword(s):  
Reynolds Number ◽  
Cross Sections ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Surface Boundary ◽  
Experimental Proof ◽  
Surface Boundary Layer ◽  
Pitch Moment ◽  
The Mean ◽  
High Reynolds

Abstract The aerodynamics of smooth and slightly rough prisms with square cross-sections and sharp edges is investigated through wind tunnel experiments. Mean and fluctuating forces, the mean pitch moment, Strouhal numbers, the mean surface pressures and the mean wake profiles in the mid-span cross-section of the prism are recorded simultaneously for Reynolds numbers between 1$$\times$$ × 10$$^{5}$$ 5 $$\le$$ ≤ Re$$_{D}$$ D $$\le$$ ≤ 1$$\times$$ × 10$$^{7}$$ 7 . For the smooth prism with $$k_s$$ k s /D = 4$$\times$$ × 10$$^{-5}$$ - 5 , tests were performed at three angles of incidence, i.e. $$\alpha$$ α = 0$$^{\circ }$$ ∘ , −22.5$$^{\circ }$$ ∘ and −45$$^{\circ }$$ ∘ , whereas only both “symmetric” angles were studied for its slightly rough counterpart with $$k_s$$ k s /D = 1$$\times$$ × 10$$^{-3}$$ - 3 . First-time experimental proof is given that, within the accuracy of the data, no significant variation with Reynolds number occurs for all mean and fluctuating aerodynamic coefficients of smooth square prisms up to Reynolds numbers as high as $$\mathcal {O}$$ O (10$$^{7}$$ 7 ). This Reynolds-number independent behaviour applies to the Strouhal number and the wake profile as well. In contrast to what is known from square prisms with rounded edges and circular cylinders, an increase in surface roughness height by a factor 25 on the current sharp-edged square prism does not lead to any notable effects on the surface boundary layer and thus on the prism’s aerodynamics. For both prisms, distinct changes in the aerostatics between the various angles of incidence are seen to take place though. Graphic abstract

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