In-depth Exploration of the Multigrid Method to Simulate Elastohydrodynamic Line Lubrications with Smooth, Wavy, and Rough Surfaces

2021 ◽  
pp. 1-24
Author(s):  
Shuangbiao Liu ◽  
Liangwei Qiu ◽  
Xiaoyang Chen
Keyword(s):  
Reynolds Equation ◽  
Multigrid Method ◽  
High Efficiency ◽  
Rough Surfaces ◽  
Mass Conservation ◽  
Boundary Line ◽  
Relaxation Processes ◽  
Restriction Operator ◽  
Relaxation Factors ◽  
Further Development

Abstract Due to high efficiency, multigrid (MG) algorithms developed by Lubrecht and Venner or others have been widely applied to solve the Reynolds equation in lubrication simulations. However, such algorithms are complex in nature and in-depth understandings and further development are of interest. This work proposes a new restriction operator of pressure to simplify the relaxation of the load balance equation and constructs several new relaxation processes based on key options of relaxations when either pressures or changes of pressure are evaluated from the Reynolds equation. In addition, effects of cycle types, treatments of cavitation boundary, line solvers, relaxation factors, and differential schemes are revealed. This paper further implements a mass conservation algorithm into the MG code in order to deal with micro-Cavitations. Characteristics of film thickness, pressure, flow continuity, and residuals, resulting from smooth, wavy, or rough surfaces are discussed. Finally, the results from the last correction cycles at various levels are recommended to be used for better accuracy.

EHD Lubrication of Multi-Body Common-Pin Conrod Big End Bearings System

2007 ◽  
Author(s):  
Aurelian Fatu ◽  
Dominique Bonneau
Keyword(s):  
Reynolds Equation ◽  
Film History ◽  
Mass Conservation ◽  
Connecting Rod ◽  
Thrust Bearings ◽  
Ehd Lubrication ◽  
Cylindrical Coordinate ◽  
Real Behavior ◽  
Multi Body ◽  
Fully Coupled

This paper describes a model for the analysis of elastohydrodynamic (EHD) lubrication of a multi-body common-pin connecting-rod (conrod) big end bearing system. Two conrod and three thrust bearings are fully coupled in order to simulate real behavior of the system. An extended Reynolds equation including mass conservation and oil film history is solved in the big end conrod bearings. The HD behavior of the thrust bearings is simulated by a cylindrical coordinate Reynolds equation. By comparisons with classical single rod analysis results show the pertinancy of simulating twin moving conrods.

Modelling of the Lateral Lubricating Interfaces in External Gear Machines Considering the Effects of Cavitation

2018 ◽  
Author(s):  
Divya Thiagarajan ◽  
Andrea Vacca
Keyword(s):  
Conservation Laws ◽  
Research Team ◽  
Reynolds Equation ◽  
Bubble Dynamics ◽  
Mass Conservation ◽  
Gap Model ◽  
Minimum Threshold ◽  
Structure Interaction ◽  
Pressure Distributions ◽  
The Stability

This work presents an approach for evaluating the cavitating conditions encountered in the lateral lubricating interfaces which exist between floating lateral bushings and gears in external gear machines (EGMs). Previous work in the authors’ research team had resulted in the development of a full fluid-structure-interaction (FSI)-EHD lubricating model for the lateral lubricating gaps, which was also validated against experiments. However, such a model uses a very simplified and approximate approach to consider aeration or cavitating conditions in the lubricating gap, where the pressures are simply saturated to a constant minimum value during their solution whenever they cross a minimum threshold. This subsequently results in numerically unstable predictions of pressure when substantial cavitating regions are encountered while also violating mass conservation laws. To overcome these issues, this paper presents a stable mass conserving cavitation algorithm by implementing the universal Reynolds equation in the existing FSI-EHD model which is applicable for both full film and cavitating conditions and has been found to be applicable in several other tribological interfaces. Such a method offers to predict the onset and shape of the cavitating regions without the need for considering complex bubble dynamics. After outlining the formulation and implementation of the new cavitation algorithm, this paper also presents simulations of a commercially available EGM, where using this cavitation algorithm was found to predict realistic pressure distributions in the lubricating interface while also maintaining the stability of such a complex lubricating gap model for EGMs.

Multigrid method for the solution of EHL point contact with bio-based oil as lubricants for smooth and rough asperity

2018 ◽  
Vol 70 (4) ◽  
pp. 599-611 ◽  
Author(s):  
Vishwanath B. Awati ◽  
Shankar Naik ◽  
Mahesh Kumar N.
Keyword(s):  
Design Methodology ◽  
Reynolds Equation ◽  
Multigrid Method ◽  
Approximation Scheme ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Alternative Source ◽  
Content Type ◽  
Longitudinal Roughness ◽  
Isothermal Case

Purpose The purpose of this paper is to study the elastohydrodynamic lubrication point contact problem with bio-based oil as lubricants for an isothermal case. The simulation of the problem is analyzed on smooth and rough asperity. Design/methodology/approach The modified Reynolds equation is discretized using finite difference and multigrid method with full approximation scheme (FAS), applied for its solution with varying load and speed. Findings This paper traces out the comparison of minimum and central film thickness with the standard formulation of Hamrock and Dowson. The effect of longitudinal roughness on surfaces is investigated by means of numerical simulations. Originality/value The results obtained are comparable with the standard results, and are shown by graphs and tables. Bio-based products bring out an alternative source of lubricant to reduce energy crises.

Preparation and Mechanism Analysis of High-Efficiency early Strength Agent

2012 ◽  
Vol 535-537 ◽  
pp. 2483-2487 ◽  
Author(s):  
Ming Sheng Zhang
Keyword(s):  
Cement Hydration ◽  
High Efficiency ◽  
Calcium Nitrate ◽  
Xrd Analysis ◽  
Mechanism Analysis ◽  
Hydration Products ◽  
Mineral Formation ◽  
Early Strength ◽  
Further Development

High-efficiency early strength agents were obtained which included triethanolamine, glycol and calcium nitrate. Then it was tested for concrete. Though text, we find that the compressive strength and flexural strength of the specimen, use of the high-efficiency early strength agent is greatly improved than with its much better not to use high-efficiency early strength agent. With time go on, high-efficiency early strength agent added does not make the strength of concrete worse, but better. Using SEM and XRD analysis technology text high-efficiency early strength agent by adding performances of concrete, including the degree of cement hydration, the morphology of hydration products and the composition of mineral formation. Analysis of the role of high-efficiency early strength agents from the perspective of the mechanism. Identified high-efficiency early strength agent impact on the cement hydration, for the further development of early strength agent to provide a theoretical basis.

scholarly journals Hydrodynamic lubrication of rough surfaces

1982 ◽  
Vol 383 (1785) ◽  
pp. 439-446 ◽  
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Hydrodynamic Lubrication ◽  
Rough Surfaces ◽  
Homogenization Method ◽  
Squeeze Film ◽  
Spatial Average

Using the two-space homogenization method we derive an averaged Reynolds equation that is correct to O (< H 6 > — < H 3 > 2 ), where H is the total film thickness and the angle brackets denote a spatial average. Applications of this mean Reynolds equation to a squeeze-film bearing with a sinusoidal or an isotropic surface roughness are discussed.

Numerical Simulation of Elastohydrodynamically Lubricated Contacts With Rough Surfaces

1994 ◽  
Vol 47 (6S) ◽  
pp. S221-S227 ◽  
Author(s):  
Alan Xiaolan Ai ◽  
Herbert S. Cheng
Keyword(s):  
Numerical Simulation ◽  
Surface Roughness ◽  
Numerical Analysis ◽  
Convective Flow ◽  
Multigrid Method ◽  
Rough Surfaces ◽  
Point Contacts ◽  
Random Roughness ◽  
Lubricated Contacts ◽  
Lubricant Flow

Transient numerical analysis to elastohydrodynamically lubricated point contacts with rough surfaces is described. The numerical simulation is based on the multigrid method. Three types of surface roughness: single dent or bump, oblique waviness and random roughness are reviewed. Under heavily loaded conditions, results reveal a strong domination of Couette flow (convective flow). The presence of sliding greatly increases pressure fluctuation and as a consequence may lead to surface-initiated spallings. For obliquely orientated roughness, lubricant flow intends to deform the ridges and create primarily longitudinal passages.

670nm Single Wavelength Nd:YAG Ceramic Laser

2013 ◽  
Vol 321-324 ◽  
pp. 482-485
Author(s):  
Zhi Chao Wu ◽  
Xiu Li Zhang
Keyword(s):  
High Power ◽  
Doping Concentration ◽  
High Efficiency ◽  
Frequency Doubling ◽  
Single Pulse ◽  
Intracavity Frequency ◽  
Propagation Matrix ◽  
Ceramic Laser ◽  
Laser Diode Arrays ◽  
Further Development

The Nd:YAG ceramic laser at 670 nm was studied by means of dispersion prism and KTP intracavity-frequency-doubling. We designed and optimized the cavity parameters by MatrixLaser software based on the standard ABCD ray propagation matrix. By using the laser diode arrays side-pumped Nd:YAG ceramic crystal with Nd doping concentration of 1.1at% and dimension of Φ3×50 mm, the Nd:YAG ceramic laser at 670 nm was realized. Under repetition rate of 1 000Hz and single pulse pumped energy of 144 mJ, the output energy of 5.1mJ at 670 nm is obtained. The optic-optic efficiency is 3.54%. The results not only formed the basis for the further development of the high power and high efficiency ceramic red laser, but also provided a great prospect for the high power ceramic red laser in the field of medical treatment, color display and other areas of application.

scholarly journals Medical thermography: capabilities and perspectives

2018 ◽  
Vol 99 (2) ◽  
pp. 264-270 ◽  
Author(s):  
A M Morozov ◽  
E M Mokhov ◽  
V A Kadykov ◽  
A V Panova
Keyword(s):  
Human Body ◽  
Thermal Imaging ◽  
Diagnostic Method ◽  
High Efficiency ◽  
Clinical Medicine ◽  
Modern Medicine ◽  
Wide Range ◽  
History Of ◽  
Further Development ◽  
Physical Principles

Medical thermography is a modern diagnostic method that is currently gaining popularity due to high informative value and non-invasiveness. The aim of the study was to review the capabilities and prospects of medical thermography in modern medicine. The analysis of domestic and foreign literature on the application of medical thermography methods for the period of 2012-2017 was performed. The article presents the capabilities of imaging in various fields of medicine, evaluates the prospects of further development of the method, advances and disadvantages of thermography were identified. It also provides the review of the application of medical infrared thermography in clinical medicine. The experience of thermography application in various medical fields was investigated: angiology, otolaryngology, surgery, neurology, obstetrics and gyenecology, etc. Apart from medical aspects of this topic, the article discusses the history of medical thermography as well as provides the physical principles of this method. At present, thermal imaging can solve a wide range of problems: determining the presence of changes in the human body, and, as a result, the probability of pathology development, monitoring the effectiveness of treatment and rehabilitation. Every year more and more studies are carried out, confirming the high efficiency, reliability and safety of thermography, thermographic screenings are suggested, that can be assumed as prediction of future method's popularity.

scholarly journals Improved design of InGaP/GaAs//Si tandem solar cells

2021 ◽  
Vol 12 ◽  
pp. 1
Author(s):  
Santiago Torres-Jaramillo ◽  
Roberto Bernal-Correa ◽  
Arturo Morales-Acevedo
Keyword(s):  
Solar Cells ◽  
Silicon Solar Cell ◽  
High Efficiency ◽  
Optimization Procedure ◽  
Optimized Design ◽  
Optimum Thickness ◽  
Tandem Solar Cells ◽  
Development Costs ◽  
Improved Design ◽  
Further Development

Optimizing any tandem solar cells design before making them experimentally is an important way of reducing development costs. Hence, in this work, we have used a complete analytical model that includes the important effects in the depletion regions of the III-V compound cells in order to simulate the behavior of two and four-terminal InGaP/GaAs//Si tandem solar cells for optimizing them. The design optimization procedure is described first, and then it is shown that the expected practical efficiencies at 1 sun (AM1.5 spectrum) for both two and four-terminal tandem cells can be around 40% when the appropriate thickness for each layer is used. The optimized design for both structures includes a double MgF2/ZnS anti-reflection layer (ARC). The results show that the optimum thicknesses are 130 (MgF2) and 60 nm (ZnS), respectively, while the optimum InGaP thickness is 220 nm and GaAs optimum thickness is 1800 nm for the four-terminal tandem on a HIT silicon solar cell (with total tandem efficiency around 39.8%). These results can be compared with the recent record experimental efficiency around 35.9% for this kind of solar cells. Therefore, triple junction InGaP/GaAs//Silicon tandem solar cells continue being very attractive for further development, using high efficiency HIT silicon cell as the bottom sub-cell.

scholarly journals Research Progress on Toxicity of Natural Compounds

2021 ◽  
Vol 5 (2) ◽  
Author(s):  
Zhangping Zhou ◽  
Zilong Fu ◽  
Yan Li ◽  
Biao Ren ◽  
Ling Duan ◽  
...  
Keyword(s):  
Natural Resources ◽  
High Efficiency ◽  
Natural Compounds ◽  
Research Progress ◽  
Rational Utilization ◽  
Active Compounds ◽  
Natural Substances ◽  
Low Toxicity ◽  
Further Development ◽  
Active Substances

There are many active substances in natural resources. After years of research, researchers at home and abroad have extracted active compounds and proved that these compounds have low toxicity and high efficiency, but the toxicity of these compounds cannot be ignored. In this paper, the research progress on the toxicity of compounds isolated from various natural substances is reviewed, which provides a reference for the further development and rational utilization of natural compounds.

Sign in / Sign up

Export Citation Format

Share Document