Theoretical Modelling of Thin Air Film Thickness in Miscible Liquids

2022 ◽  
pp. 817-824
Author(s):  
Vijayakumar Mathaiyan ◽  
R. Vijayanandh ◽  
Dong Won Jung
Keyword(s):  
Film Thickness ◽  
Theoretical Modelling ◽  
Miscible Liquids ◽  
Air Film

Rough Air-Soft Elastohydrodynamic Lubrication

2013 ◽  
Vol 420 ◽  
pp. 30-35
Author(s):  
Khanittha Wongseedakaew ◽  
Jesda Panichakorn
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Modulus Of Elasticity ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Multilevel Methods ◽  
Inlet Temperature ◽  
Film Pressure ◽  
Air Inlet ◽  
Air Film

This paper presents the effects of rough surface air-soft elastohydrodynamic lubrication (EHL) of rollers for soft material under the effect of air molecular slip. The time independent modified Reynolds equation and elasticity equation were solved numerically using finite different method, Newton-Raphson method and multigrid multilevel methods were used to obtain the film pressure profiles and film thickness in the contact region. The effects of amplitude of surface roughness, modulus of elasticity and air inlet temperature are examined. The simulation results showed surface roughness has effect on film thickness but it little effect to air film pressure. When the amplitude of surface roughness and modulus of elasticity increased, the air film thickness decreased but air film pressure increased. However, the air inlet temperature increased when the air film thickness increased.

scholarly journals Optimal Design for the Structure Parameters of Long Raster Engraving Air-floating Platform

Mechanika ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 55-63
Author(s):  
Deyun Mo
Keyword(s):  
Film Thickness ◽  
Element Model ◽  
Structure Design ◽  
Test Method ◽  
Loading Capacity ◽  
Three Dimension ◽  
Floating Platform ◽  
Range Analysis ◽  
Orthogonal Test Method ◽  
Air Film

Air-floating platform is the core component of long raster engraving system. In order to design an air-floating platform to greatly meet the demands of long raster engraving, this paper, based on the validation of simulation model accuracy by test platform, proposes a three-dimension finite element model about gas film, and investigates the influence of the gas film thickness, air pressure and width of bottom guideway on the loaded capacity and air consumption by orthogonal test method. Then the best design plan of air-floating platform structure was determined by range analysis method. The results showed that air film thickness H=0.02 mm, gas supply pressure Ps=0.15 MPa, width of bottom guideway Bx=140 mm, the loading capacity of single-sided guideway is about 3177 N, its air consumption is 191487 mm3/s. Hence, this plan can not only meet the requirements of the loading capacity but also reduce air consumption of air-floating platform so as to provide a basis for optimum structure design about air-floating platform.

The Effect of Disk Warpage/Skew on the Deflection and Vibration of a Flexible Disk Spinning Above a Baseplate and in Contact With a Point-Head

1997 ◽  
Vol 119 (1) ◽  
pp. 64-70 ◽  
Author(s):  
R. Y. Wu ◽  
G. G. Adams
Keyword(s):  
Film Thickness ◽  
Rotational Speed ◽  
Numerical Solutions ◽  
Point Contact ◽  
Angle Variation ◽  
Coupled Equations ◽  
Close Proximity ◽  
Small Change ◽  
Flexible Disk ◽  
Air Film

A flexible disk, with small initial warpage/skew, is spinning in close proximity to a stationary baseplate. The partial differential equation for the disk deflection is coupled to the Reynolds equation of the stabilizing air-film. Disk warpage/skew produces a small change in the deflection which rotates with the disk. These deflections are obtained by linearizing the coupled equations about the axisymmetric configuration corresponding to a perfect disk. Numerical solutions are obtained and compared for different values of rotational speed and air-film thickness. The results show that among the three skewed/warped disks modeled, the skewed disk (i.e., the plane of the disk is skewed with respect to its axis of rotation) produces the largest deflection change (axial runout). With the effect of a point-contact head included, the existence of disk warpage/skew causes the head to produce a spatially-fixed harmonically varying force. The total disk motion is determined by superposition of the deflection pattern fixed on the disk and the space-fixed head-induced vibration. The disk pitch angle variation at the head is obtained and the results are compared for various values of the rotational speed and air-film thickness.

scholarly journals Droplet levitation over a moving wall with a steady air film

2019 ◽  
Vol 862 ◽  
pp. 261-282 ◽  
Author(s):  
Erina Sawaguchi ◽  
Ayumi Matsuda ◽  
Kai Hama ◽  
Masafumi Saito ◽  
Yoshiyuki Tagawa
Keyword(s):  
Free Surface ◽  
Film Thickness ◽  
Surface Velocity ◽  
Pressure Balance ◽  
Local Pressure ◽  
Interferometric Method ◽  
Wall Velocity ◽  
Wide Range ◽  
Shape Oscillation ◽  
Air Film

In isothermal non-coalescence behaviours of a droplet against a wall, an air film of micrometre thickness plays a crucial role. We experimentally study this phenomenon by letting a droplet levitate over a moving glass wall. The three-dimensional shape of the air film is measured using an interferometric method. The mean curvature distribution of the deformed free surface and the distributions of the lubrication pressure are derived from the experimental measurements. We vary experimental parameters, namely wall velocity, droplet diameter and viscosity of the droplets, over a wide range; for example, the droplet viscosity is varied over two orders of magnitude. For the same wall velocity, the air film of low-viscosity droplets shows little shape oscillation with constant film thickness (defined as the steady state), while that of highly viscous droplets shows a significant shape oscillation with varying film thickness (defined as the unsteady state). The droplet viscosity also affects the surface velocity of a droplet. Under our experimental conditions, where the air film shape can be assumed to be steady, we present experimental evidence showing that the lift force generated inside the air film balances with the droplet’s weight. We also verify that the lubrication pressure locally balances with the surface tension and hydrostatic pressures. This indicates that lubrication pressure and the shape of the free surface are mutually determined. Based on the local pressure balance, we discuss a process of determining the steady shape of an air film that has two areas of minimum thickness in the vicinity of the downstream rim.

On Controlling the Film Thickness in Self-Acting Foil Bearings

1970 ◽  
Vol 92 (2) ◽  
pp. 359-362 ◽  
Author(s):  
A. Eshel
Keyword(s):  
Film Thickness ◽  
Free Path ◽  
Marked Effect ◽  
Solid Wall ◽  
Mean Free Path ◽  
Radius Of Curvature ◽  
Air Gaps ◽  
Foil Bearings ◽  
Foil Bearing ◽  
Air Film

Some factors useful in overcoming excessive air gaps in foil bearings are investigated. Since the gaps of interest are small, the foil bearing equations are modified to include the effects of the molecular mean free path. It is shown that by small corners in the solid wall, one can reduce the air film thickness considerably. A change in curvature with continuous slope has also a marked effect on the film thickness. Theoretical prediction curves allowing the calculation of the air gap as a function of corner angle, change in radius of curvature, and the molecular mean free path are presented.

scholarly journals Levitation of a drop over a moving surface

2013 ◽  
Vol 733 ◽  
Author(s):  
Henri Lhuissier ◽  
Yoshiyuki Tagawa ◽  
Tuan Tran ◽  
Chao Sun
Keyword(s):  
Film Thickness ◽  
Wall Motion ◽  
Angular Position ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Capillary Length ◽  
Large Velocity ◽  
Rotating Hollow Cylinder ◽  
Drag And Lift ◽  
Air Film

AbstractWe investigate the levitation of a drop gently deposited onto the inner wall of a rotating hollow cylinder. For a sufficiently large velocity of the wall, the drop steadily levitates over a thin air film and reaches a stable angular position in the cylinder, where the drag and lift balance the weight of the drop. Interferometric measurements yield the three-dimensional (3D) air film thickness under the drop and reveal the asymmetry of the profile along the direction of the wall motion. A two-dimensional (2D) model is presented which explains the levitation mechanism, captures the main characteristics of the air film shape and predicts two asymptotic regimes for the film thickness ${h}_{0} $: for large drops ${h}_{0} \sim {\mathit{Ca}}^{2/ 3} { \kappa }_{b}^{- 1} $, as in the Bretherton problem, where $\mathit{Ca}$ is the capillary number based on the air viscosity and ${\kappa }_{b} $ is the curvature at the bottom of the drop; for small drops ${h}_{0} \sim {\mathit{Ca}}^{4/ 5} {(a{\kappa }_{b} )}^{4/ 5} { \kappa }_{b}^{- 1} $, where $a$ is the capillary length.

High Knudsen Number Molecular Rarefaction Effects in Gas-Lubricated Slider Bearings for Computer Flying Heads

1987 ◽  
Vol 109 (2) ◽  
pp. 276-282 ◽  
Author(s):  
Y. Mitsuya ◽  
T. Ohkubo
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Flow Model ◽  
Slip Flow ◽  
Ambient Air ◽  
Mean Free Path ◽  
Lubricating Film ◽  
Modified Reynolds Equation ◽  
Air Film ◽  
Rarefaction Effects

This paper presents a study into the gas lubrication capability of an ultra-thin 0.025 μm film (converted value for ambient air film). The experimental results obtained using subambient helium as the lubricating film are compared with the calculated results using the modified Reynolds equation considering flow slippage due to the molecular mean free path effects. This comparison confirms that the slip flow model holds true within the range of the present experiments, and that the modified Reynolds equation is applicable for designing the computer flying heads operating at such thin spacing. The reason for the excellent agreement is discussed considering the locality of rarefaction effects on the lubricating surfaces and the anisotropy of these effects between the film thickness and the slider width.

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