Lift forces on three-dimensional elastic and viscoelastic lubricated contacts

2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Arash Kargar-Estahbanati ◽  
Bhargav Rallabandi
Keyword(s):  
Three Dimensional ◽  
Lubricated Contacts ◽  
Lift Forces

Numerical Investigation of the Drag and Lift Forces Acting on Impenetrable Rotating Spherical Nano-Particle

2008 ◽  
Author(s):  
M. R. Meigounpoory ◽  
A. Rahi ◽  
A. Mirbozorgi
Keyword(s):  
Lift Coefficient ◽  
Three Dimensional ◽  
Slip Boundary Condition ◽  
Slip Condition ◽  
Nano Particle ◽  
Slip Coefficient ◽  
Slip Boundary ◽  
Lift Forces ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

The drag and lift forces acting on a rotating impenetrable spherical suspended nano-particle in a homogeneous uniform flow are numerically studied by means of a three-dimensional numerical simulation with slip boundary condition. The effects of both the slip coefficient and rotational speed of the nanosphere on the drag and lift forces are investigated for Reynolds numbers in the range of 0.1 < Re < 100. Increase of rotation increases the drag and lift force exerted by flow at the surface of nano-sphere. By increasing slip coefficient the values of drag and lift coefficients decreases. At full slip condition, rotation of the nano-sphere has not significant effects on the drag and lift coefficient values moreover the lift coefficient of flow around the rotating spherical particle will be vanished. Present numerical results at no-slip condition are in good agreements with certain results of flow around of rotating sphere.

The development and application of the spacer layer imaging method for measuring lubricant film thickness

2001 ◽  
Vol 215 (3) ◽  
pp. 261-277 ◽  
Author(s):  
H. A. Spikes ◽  
P. M. Cann
Keyword(s):  
Film Thickness ◽  
Boundary Lubrication ◽  
Three Dimensional ◽  
Spectrometric Analysis ◽  
Imaging Method ◽  
Lubricated Contacts ◽  
Film Distribution ◽  
Spacer Layer ◽  
Lubricant Films ◽  
The 1960S

This paper reviews the historical development of optical interferometry as applied to the study of lubricant films. The technique was first applied to lubricated contacts in the 1960s, when it played an important role in the validation of the elastohydrodynamic theory of lubrication. Initially the method was not suited to the study of mixed and boundary lubrication because it could not measure film thicknesses of less than about 50 nm. In the 1970s, however, this limitation was partially overcome by the use of a spacer layer and this, coupled in the early 1990s with spectrometric analysis of the interfered light, enabled films down to just 1 nm thick to be measured in lubricated contacts, well within the boundary lubrication regime. Recently a number of workers have applied colorimetric image analysis to optical interference images to enable accurate three-dimensional maps of film distribution in lubricated contacts to be determined. This approach, coupled with the use of a spacer layer, has led to the spacer layer imaging method, which can map film thickness in boundary and mixed lubricated contact. Some recent applications of this technique are described.

Numerical Study on Deformation Behavior of a Fluid Particle Under Shear Flow

2011 ◽  
Author(s):  
Youngho Suh ◽  
Changhoon Lee
Keyword(s):  
Shear Flow ◽  
Deformation Behavior ◽  
Present Method ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Conditions ◽  
Droplet Deformation ◽  
Lift Forces ◽  
Drag And Lift ◽  
Acting Force

In this work, we studied the deformation behavior of a droplet under the various flow conditions. The droplet deformation is calculated by a level-set method. In order to determine the acting force on a particle in shear flow field, we propose the feedback forces which can maintain particle position with efficient handling of deformation. Computations were carried out to investigate the deformation behavior of a droplet caused by the surrounding gaseous flow and the effect of the deformation on the droplet characteristics with various dimensionless parameters. Based on the numerical results, we observed that drag and lift forces acting on a droplet depend strongly on the deformation. Also, the present method is proven to be applicable to a three-dimensional deformation of droplet in shear flow, which cannot be properly analyzed by the previous studies. The drag and lift forces obtained from the present numerical method are favorably compared with the data reported in the literature.

Hydrodynamic Characteristics of a Swimmer’s Hand

1999 ◽  
Vol 15 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Ross H. Sanders
Keyword(s):  
Entire Range ◽  
Three Dimensional ◽  
Hydrodynamic Characteristics ◽  
Large Contribution ◽  
Towing Tank ◽  
Hand Orientation ◽  
Resin Cast ◽  
Lift Forces ◽  
Direction Opposite

The main purpose of this study was to develop a model for calculating forces produced by a swimmer’s hand, with the thumb adducted, accelerating in the direction of flow. The model included coefficients to account for the velocity and acceleration of the hand. These coefficients were designed to calculate forces in the direction opposite the motion (drag) and two components of lift orthogonal to the direction of motion. To determine the coefficients, three-dimensional forces acting on a resin cast of a swimmer’s hand were recorded while accelerating the hand from rest to 0.45 m · s−1 and 0.6 m · −1 in a towing tank. The hand orientation was varied throughout the entire range at 5° increments. Three-dimensional surfaces describing the magnitude of the coefficients as functions of pitch and sweepback angle were produced. It was found that acceleration coefficients as well as velocity coefficients are required for accurate modeling of the forces produced by the hand in swimming. The forces generated by the hand are greatest when pitch angles approach 90° due to the large contribution by the drag component. However, at pitch angles near 45° and sweepback angles near 45° and 135°, lift forces contribute substantially.

Debris Denting Effects on Elastohydrodynamic Lubricated Contacts

1997 ◽  
Vol 119 (3) ◽  
pp. 579-587 ◽  
Author(s):  
Gang Xu ◽  
Farshid Sadeghi ◽  
J. David Cogdell
Keyword(s):  
Finite Element ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Element Model ◽  
Von Mises Stress ◽  
Internal Stresses ◽  
Element Analysis ◽  
Lubricated Contacts

A finite element model was developed to investigate the effects of a spherical debris on elastohydrodynamically lubricated rolling/sliding contacts. Three dimensional dent profiles were obtained using finite element method showing horseshoe shape material pile-up along the rolling direction. The dent profiles obtained from the finite element analysis (FEA) were compared with the experimental results. There is good qualitative agreement between FEA and experimental dent profiles. The FEA dent profiles were then used in a time dependent thermal elastohydrodynamic lubrication (EHL) point contact model to analyze the dent effects on the pressure, film thickness and temperature profiles. The presence of a dent in lubricated contacts generates high pressure spikes and increases the peak temperature. The internal stresses were calculated based on the pressure and traction data obtained from the EHL analysis. The results indicate that a dent created by a debris will cause the internal maximum Von Mises stress to occur near the surface, which contributes to surface initiated failures.

The Influence of Surface Patterning on the Thermal Properties of Textured Thrust Bearings

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Surrogate Model ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Three Dimensional ◽  
Major Axis ◽  
Friction Torque ◽  
Design Parameters ◽  
Textured Surfaces ◽  
Lubricated Contacts ◽  
Radial Extent

Contact performance can be enhanced by using textured surfaces. These are also found to have influences on lubricated contacts. A procedure to find the optimal partially textured thrust bearing configuration is presented in this study. A parallel sector-pad thrust bearing is simulated by a three-dimensional (3D) computational fluid dynamics (CFD) model. The stationary surface of the bearing is textured with dimples, while the rotor surface is flat. The results of the baseline model are validated by experimental data. In this study, we compare rectangular and elliptical dimples by investigating design parameters, such as major the length of the major axis (width), the length of the minor axis (length), dimple depth, circumferential space between two dimples, radial space between two dimples, radial extent, circumferential extent are selected as design parameters. A parametric study is conducted to investigate the influence of the texture geometries and a surrogate model is created. Based on the surrogate model, a multi-objective optimization scheme is used to navigate the design space and find the optimal texture structure that provides a lower maximal temperature inside the fluid film, higher load capacity, and lower friction torque. The results show that the optimal radial extent of the texture is around 80% of the pad radial length for both cases. The optimal length of the elliptical dimples in the circumferential direction is about 30% larger than the value of the rectangular dimples. In the final optimal design, the maximal temperature reduces 1.1% and 1.3% for rectangular and elliptical dimples while the load capacities are maintained at the same level.

scholarly journals Concurrent Multiscale Simulations of Rough Lubricated Contact of Aluminum Single Crystal

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 965
Author(s):  
Jie Zhang ◽  
Lihong Su ◽  
Zhongnan Wang
Keyword(s):  
Single Crystal ◽  
Contact Area ◽  
Three Dimensional ◽  
Domain Size ◽  
Md Simulations ◽  
Multiscale Simulation ◽  
Computational Time ◽  
Aluminum Single Crystal ◽  
Lubricated Contacts ◽  
Lubricated Contact

In this paper, a concurrent multiscale simulation strategy coupling atomistic and continuum models was proposed to investigate the three-dimensional contact responses of aluminum single crystal under both dry and lubricated conditions. The Hertz contact is performed by using both the multiscale and full molecular dynamics (MD) simulations for validation. From the contact area, kinetic energy and stress continuity aspects, the multiscale model shows good accuracy. It can also save at least five times the computational time compared with the full MD simulations for the same domain size. Furthermore, the results of lubricated contact show that the lubricant molecules could effectively cover the contact surfaces; thereby separating the aluminum surfaces and bearing the support loads. Moreover, the surface topography could be protected by the thin film formed by the lubricant molecules. It has been found that the contact area decreases obviously with increasing the magnitude of load under both dry and lubricated contacts. Besides, a decrease in contact area is also seen when the number of lubricant molecules increases. The present study has confirmed that the dimension of lubricated contacts could be greatly expanded during the simulation using the proposed multiscale method without sacrificing too much computational time and accuracy.

An Average Flow Model for Determining Effects of Three-Dimensional Roughness on Partial Hydrodynamic Lubrication

1978 ◽  
Vol 100 (1) ◽  
pp. 12-17 ◽  
Author(s):  
Nadir Patir ◽  
H. S. Cheng
Keyword(s):  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Surface Characteristic ◽  
Correlation Lengths ◽  
Lubricated Contacts ◽  
Empirical Relations ◽  
Numerical Flow Simulation

A new approach is utilized to determine the effects of surface roughness on partially lubricated contacts. An average Reynolds equation for rough surfaces is defined in terms of pressure and shear flow factors, which are obtained by numerical flow simulation. Through the use of measured or numerically generated rough surfaces, any three dimensional roughness structure can be analyzed with this method. The average Reynolds equation is obtained for isotropic surfaces, and for surfaces with directional patterns. The flow factors for these surfaces are expressed as empirical relations in terms of h/σ and a surface characteristic γ defined as the ratio of x and y correlation lengths.

The orbit of Pluto over a long interval of time

1966 ◽  
Vol 25 ◽  
pp. 227-229 ◽  
Author(s):  
D. Brouwer
Keyword(s):  
Periodic Orbit ◽  
Numerical Integration ◽  
Restricted Problem ◽  
Three Dimensional ◽  
The Third ◽  
Circular Restricted Problem ◽  
Resonance Relation

The paper presents a summary of the results obtained by C. J. Cohen and E. C. Hubbard, who established by numerical integration that a resonance relation exists between the orbits of Neptune and Pluto. The problem may be explored further by approximating the motion of Pluto by that of a particle with negligible mass in the three-dimensional (circular) restricted problem. The mass of Pluto and the eccentricity of Neptune's orbit are ignored in this approximation. Significant features of the problem appear to be the presence of two critical arguments and the possibility that the orbit may be related to a periodic orbit of the third kind.

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