scholarly journals Film Thickness in Slender Elliptic Contacts

2021 ◽  
Author(s):  
Marius Wolf
Keyword(s):  
Film Thickness ◽  
State Of The Art ◽  
Asymptotic Solutions ◽  
Large Parameter ◽  
Parameter Domain ◽  
Simulation Results ◽  
New Formula ◽  
Increasing Load

In this paper, analytical equations for the central film thickness in slender elliptic contacts are investigated. A comparison of state-of-the-art formulas with simulation results of a multilevel EHL solver is conducted and shows considerable deviation. Therefore, a new film thickness formula for slender elliptic contacts with variable ellipticity is derived. It incorporates asymptotic solutions, which results in validity over a large parameter domain. It captures the behaviour of increasing film thickness with increasing load for specific very slender contacts. The new formula proves to be significantly more accurate than current equations.

Film thickness in elastohydrodynamically lubricated slender elliptic contacts: Part I – numerical studies of central film thickness

2021 ◽  
pp. 135065012110477
Author(s):  
Marius Wolf ◽  
Sergey Solovyev ◽  
Fatemi Arshia
Keyword(s):  
Film Thickness ◽  
State Of The Art ◽  
Experimental Studies ◽  
Elastohydrodynamic Lubrication ◽  
Large Parameter ◽  
Numerical Studies ◽  
Minimum Film Thickness ◽  
Subsequent Publication ◽  
New Formula ◽  
Increasing Load

In this paper, analytical equations for the central film thickness in slender elliptic contacts are investigated. A comparison of state-of-the-art formulas with simulation results of a multilevel elastohydrodynamic lubrication solver is conducted and shows considerable deviation. Therefore, a new film thickness formula for slender elliptic contacts with variable ellipticity is derived. It incorporates asymptotic solutions, which results in validity over a large parameter domain. It captures the behaviour of increasing film thickness with increasing load for specific very slender contacts. The new formula proves to be significantly more accurate than current equations. Experimental studies and discussions on minimum film thickness will be presented in a subsequent publication.

Analysis of Center Detonation Characteristics of Water Mist

2014 ◽  
Vol 602-605 ◽  
pp. 3434-3437
Author(s):  
Yu Kun Chen ◽  
Ke Yin Wang ◽  
Hai Ying Huang ◽  
Pai Hang Zhao
Keyword(s):  
Theoretical Model ◽  
Theoretical Calculation ◽  
Water Mist ◽  
Correction Factors ◽  
Simulation Results ◽  
New Formula ◽  
Detonation Characteristics

This paper analyzed the formula for calculating the velocity and scatter radius of water mist droplets after detonation. Through establishing model, calculating by the formula and simulation of theoretical model, the reasons of deviation between calculation and simulation results were found out. In order to make theoretical calculation more accurate and applicable, new formula was created by introducing correction factors.

NUMERICAL INVESTIGATION OF FILM DISTRIBUTION IN HORIZONTAL-TUBE FALLING FILM EVAPORATOR

2011 ◽  
Vol 19 (03) ◽  
pp. 177-183 ◽  
Author(s):  
JIN-BO CHEN ◽  
QING-GANG QIU
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Film Thickness ◽  
Liquid Film ◽  
Numerical Investigation ◽  
Horizontal Tube ◽  
Flow Density ◽  
Falling Film ◽  
Film Distribution ◽  
Simulation Results

The technique of horizontal-tube falling film has been used in the cooling and heating industries such as refrigeration systems, heating systems and ocean thermal energy conversion systems. The comprehensive performance of evaporator is directly affected by the film distribution characteristics outside tubes. In this paper, numerical investigation was performed to predict the film characteristics outside the tubes in horizontal-tube falling film evaporator. The effects of liquid flow rate, tube diameter and the circular degree of tube on the film thickness were presented. The numerical simulation results were compared with that of the empirical equations for calculating the falling film thickness, and agreements between them were reasonable. Numerical simulation results show that, at the fixed fluid flow density, the liquid film is thicker on the upper and lower tube and the thinnest liquid film appears at angle of about 120°. The results also indicate that, when the fluid flow density decreases to a certain value, the local dryout spot on the surface of the tube would occur. In addition, the film thickness decreases with the increases of the tube diameter at the fixed fluid flow density.

scholarly journals COVID-19 Diagnosis Using Capsule Network and Fuzzy C -Means and Mayfly Optimization Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Ali Farki ◽  
Zahra Salekshahrezaee ◽  
Arash Mohammadi Tofigh ◽  
Reza Ghanavati ◽  
Behdad Arandian ◽  
...  
Keyword(s):  
State Of The Art ◽  
Optimal Method ◽  
X Ray ◽  
Suggested Technique ◽  
Improve Accuracy ◽  
Sensitivity Rate ◽  
Chest X Ray ◽  
Therapeutic Measures ◽  
Simulation Results ◽  
Day By Day

The COVID-19 epidemic is spreading day by day. Early diagnosis of this disease is essential to provide effective preventive and therapeutic measures. This process can be used by a computer-aided methodology to improve accuracy. In this study, a new and optimal method has been utilized for the diagnosis of COVID-19. Here, a method based on fuzzy C -ordered means (FCOM) along with an improved version of the enhanced capsule network (ECN) has been proposed for this purpose. The proposed ECN method is improved based on mayfly optimization (MFO) algorithm. The suggested technique is then implemented on the chest X-ray COVID-19 images from publicly available datasets. Simulation results are assessed by considering a comparison with some state-of-the-art methods, including FOMPA, MID, and 4S-DT. The results show that the proposed method with 97.08% accuracy and 97.29% precision provides the highest accuracy and reliability compared with the other studied methods. Moreover, the results show that the proposed method with a 97.1% sensitivity rate has the highest ratio. And finally, the proposed method with a 97.47% F 1 -score rate gives the uppermost value compared to the others.

Numerical Investigation for Characteristics and Oil-Air Distributions of a Tilting-Pad Journal Bearing Under Different Loads

2020 ◽  
Author(s):  
Aoshuang Ding ◽  
Xuesong Li
Keyword(s):  
Film Thickness ◽  
Journal Bearing ◽  
Viscosity Ratio ◽  
Cavitation Model ◽  
Tilting Pad ◽  
Sst Model ◽  
Bearing Load ◽  
Simulation Results ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

Abstract This paper analyses the flow characteristics and oil-air distributions of oil flows in a tilting-pad journal bearing under different bearing loads. This titling-pad journal bearing is working at 3000 rpm rotation speed and its minimum film thicknesses have been measured under different loads from 180 kN to 299 kN. Based on the previous researches of this bearing under 180 kN, the gaseous cavitation and low-turbulence flow exists in this bearing flow. A suitable gaseous cavitation model and the SST model with low-Re correction are used in the film flow simulations. With the rotor and pads assumed to be rigid, the dynamic mesh and motion equations are applied to simulate the motions of the rotor and the rotations of the pads. Based on the simulation results under different bearing loads, the simulated minimum film thicknesses agrees well with the measured data. It indicates that the simulation results can catch the film geometries and flows correctly. With the load increasing, the rotor moves closer to the loaded pads and the minimum film thickness decreases. Taking the effect of boundary layers into consideration, the turbulence has a negative relationship with the film thickness and decreases in the loaded area under higher bearing load. It can be verified by the simulated lower turbulent viscosity ratio distributions in the loaded pads. In the unloaded area, both the film thickness and turbulence viscosity ratio are positively related to the bearing loads. Thus, the higher bearing load may lead the flow to be more different in the loaded and unloaded area, and the turbulence in the loaded pads may transfer to laminar in the end. As for the oil-air distributions, in the unloaded pads, with the bearing load increasing, the simulated air volume fraction increases in the unloaded pads with lower pressure. It should be caused by the higher film thickness of the unloaded pads under higher loads. In sum, the flow turbulence and cavitation process changes with the bearing load. With a higher load, the cavitation becomes more in the unloaded pads and the flow changes sharper from the high-turbulence unloaded area to the low-turbulence loaded area. As the simulation results is in good accordance with the experimental data, the SST model with low-Re correction and the gaseous cavitation model are verified to be suitable for bearing film simulations under different loads.

State-of-the-Art Master Slave Flip-Flop Designs for Low Power VLSI Systems

2016 ◽  
pp. 166-198
Author(s):  
Kunwar Singh ◽  
Satish Chandra Tiwari ◽  
Maneesha Gupta
Keyword(s):  
Low Power ◽  
State Of The Art ◽  
Relative Power ◽  
Power Budget ◽  
Comprehensive Overview ◽  
Feedback Strategy ◽  
Flip Flop ◽  
Simulation Results

This chapter presents a comprehensive overview of the conventional fully static master slave flip-flops used in low power VLSI systems where power budget is critical. In addition, the chapter also presents alternative realization of fully static master-slave flip-flops utilizing a modified feedback strategy. The flip-flops designed on the basis of modified architecture have been explained in detail and compared with state-of-the-art master slave flip-flop designs available in the literature. Extensive capacitance calculations have been performed in terms of clock load and capacitance at internal nodes has also been estimated for all the flip-flop configurations. This is executed in order to compare their relative power and delay characteristics which are well supported by simulation results.

scholarly journals Tag Localization with Asynchronous Inertial-Based Shifting and Trilateration

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5204
Author(s):  
Alma’aitah ◽  
Eslim ◽  
Hassanein
Keyword(s):  
Low Power ◽  
Indoor Localization ◽  
State Of The Art ◽  
Location Estimation ◽  
Object Localization ◽  
Personal Area Networks ◽  
Matlab Simulation ◽  
Tag Localization ◽  
Simulation Results ◽  
Localization Data

Personal Area Networks (PAN) are key topologies in pervasive Internet of Things (IoT) localization applications. In the numerous object localization techniques, centralization and synchronization between the elements are assumed. In this paper, we leverage crowdsourcing from multiple fixed and mobile elements to enhance object localization. A cooperative crowdsourcing scheme is proposed to localize mobile low power tags using distributed and mobile/fixed readers for GPS assisted environments (i.e., outdoor) and fixed readers for indoors. We propose Inertial-Based Shifting and Trilateration (IBST) technique to provide an accurate reckoning of the absolute location of mobile tags. The novelty in our technique is its capability to estimate tag locations even when the tag is not covered by three readers to perform trilateration. In addition, IBST provides scalability since no processing is required by the low power tags. IBST technique is validated through extensive simulations using MATLAB. Simulation results show that IBST consistently estimates location, while other indoor localization solutions fail to provide such estimates as the state-of-the-art techniques require localization data to be available simultaneously to provide location estimation.

Study of Fluid-Solid Simulation on the Large-Scale Hydrostatic Bearing of Hollow Coaxial

2009 ◽  
Vol 628-629 ◽  
pp. 281-286 ◽  
Author(s):  
Xiang Jun Yu ◽  
Ji Xin Wang ◽  
Yong Li
Keyword(s):  
Film Thickness ◽  
Large Scale ◽  
Maximum Stress ◽  
Impact Factors ◽  
Oil Film ◽  
Hydrostatic Bearing ◽  
Simulation Results ◽  
Stress And Deformation

In order to investigate the changing law of the film thickness caused by the deformation of hollow coaxial and drum-shaped lining and accurately calculate the stress of hollow coaxial and rum-shaped lining, the fluid-solid numerical simulatied model of a large-scale hydrostatic bearing was established. The stress and deformation of hollow coaxial and drum-shaped lining was obtained by indirect coupled methods. The typical impact factors and the deformation laws of the thinnest film were discussed. The simulation results indicate that the maximum stress locatioes on the drum-shaped lining and hollow coaxial; and the deformation of the hollow coaxial is 60.47 times that of the drum-shaped lining, and the oil film thinnest thickness decreases by 12.1% due to the deformation of the hollow coaxial and drum-shaped lining; and the stiffness of the hollow coaxial makes greatest impact on oil film deformation.

Lubricant Flow and Evaporation Model for Heat Assisted Magnetic Recording Systems Including Reactive End-Group Effects and Thin-Film Viscosity

2012 ◽  
Author(s):  
Joanna E. Bechtel ◽  
David B. Bogy
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Magnetic Recording ◽  
Disjoining Pressure ◽  
Thickness Dependence ◽  
Heat Assisted Magnetic Recording ◽  
Lubricant Flow ◽  
Simulation Results ◽  
Thin Film Viscosity ◽  
Film Viscosity

The lubricant applied to the disk in a hard drive is a critical component for head-disk interface reliability. In Heat Assisted Magnetic Recording (HAMR), the heat supplied to the disk by the laser will add new thermal considerations to lubricant performance. Investigations into how the lubricant behaves at the small time and length scales seen in HAMR systems need to be conducted numerically. Published works on HAMR lubricant modeling have considered only the van der Waals contribution to disjoining pressure, commonly called the dispersive component, and do not consider the film thickness dependence of viscosity. However, lubricants with reactive end groups such as Fomblin Zdol are widely used, and such simple disjoining pressure and viscosity models do not capture certain lubricant behavior. We have developed a simulation tool that incorporates film thickness dependencies of viscosity and polar and dispersive disjoining pressure into a continuum lubrication model. We investigate the effect of initial thickness on lubricant flow and evaporation under HAMR write conditions considering both components of disjoining pressure and thin-film viscosity. Simulation results indicate the effect of including polar disjoining pressure depends on the initial lubricant thickness. The inclusion of viscosity thickness dependence does not affect simulation results under scanning laser conditions but will be important in reflow simulations.

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