Influences of Iteration Details on Flow Continuities of Numerical solutions to Isothermal Elastohydrodynamic Lubrication with Micro-Cavitations

2020 ◽  
pp. 1-28
Author(s):  
Shuangbiao Liu ◽  
Liangwei Qiu ◽  
Zhijian Wang ◽  
Xiaoyang Chen
Keyword(s):  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Iteration Process ◽  
Mass Conservation ◽  
The Other ◽  
Flow Curves ◽  
Line Contacts ◽  
Film Content ◽  
Relaxation Factors ◽  
First Time

Abstract Studying elastohydrodynamic lubrication (EHL) of line contacts involving micro-cavitations, this paper exams various numerical solutions with a focus of their explicit flow continuities from inlet to exit. For the first time, influences of relaxation details, error controls, differential schemes, and mesh densities on flow continuity in EHL are revealed in a systemic fashion. Furthermore, hybrid relaxation-factors are introduced, the line relaxation is enabled with earlier boundary condition enforcement, and a typical iteration process is updated with a three-in-one iteration control. Such a process is further integrated with two different starvation/cavitation treatments: one explicitly adjusts reformation locations, and the other uses a fractional film content parameter to adjust the Couette term originated by Bayada et al.. The mass conservation results for problems with multiple micro-cavitations occurring inside the lubrication region are compared and flow curves clearly demonstrate satisfactory continuities. These insights are beneficial for EHL simulations.

A Theoretical Approach to the Shift Mechanics of Rubber Belt Variators

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Francesco Sorge
Keyword(s):  
Numerical Solutions ◽  
Control Volume ◽  
Mass Conservation ◽  
Theoretical Description ◽  
The Other ◽  
Control Surface ◽  
Speed Ratio ◽  
Rubber Belt ◽  
Total Mass Flux ◽  
Inertia Forces

This paper proposes a theoretical description of the mechanical behavior of rubber belt variators during the speed ratio shift. Comparing with the steady operation, the mass conservation of the belt is completely reformulated considering an elementary dihedral control volume between two planes through the pulley axis and balancing the inside mass variation with the total mass flux through the control surface. On the other hand, the belt equilibrium conditions are similar to the steady case, as the inertia forces due to the shifting motion are negligible with respect to the other forces. Assuming a one-dimensional belt model, it is shown that adhesive regions may appear inside the arc of contact, where the belt sticks to the pulley flanges along spiral-shaped paths. It is demonstrated that this type of contact may occur only for the closing pulleys, differently from the steady drives and from the opening pulleys, where only quasiadhesive internal subregions may be observed at most, where the sliding velocity turns out to be quite small along a more or less extended portion of the arc of contact. Numerical solutions are calculated for all types of conditions, and their characteristics are widely described.

Traction in Thermal Elastohydrodynamic Lubrication of Rough Surfaces

1992 ◽  
Vol 114 (1) ◽  
pp. 186-191 ◽  
Author(s):  
L. Chang
Keyword(s):  
Numerical Solutions ◽  
Rough Surfaces ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Wide Range ◽  
Line Contacts ◽  
Simulation Results

This paper studies the traction behavior of elastohydrodynamically lubricated line contacts between two rough surfaces. The study uses a thermal micro-elastohydrodynamic-lubrication (micro-EHL) model and obtains traction coefficients for a wide range of operating conditions and for film parameters as small as 1.50. The simulation results suggest that the traction is generally insensitive to the roughness structure and magnitude as long as the contact maintains a full EHL film. The results also indicate clearly that the lubricant squeeze induced by the motion and interaction of rough surfaces significantly affects the numerical solutions to thermal micro-elastohydrodynamic lubrication.

A Reynolds-Eyring Equation for Elastohydrodynamic Lubrication in Line Contacts

1987 ◽  
Vol 109 (4) ◽  
pp. 648-654 ◽  
Author(s):  
T. F. Conry ◽  
S. Wang ◽  
C. Cusano
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Newtonian Flow ◽  
Line Contacts ◽  
Different Temperatures ◽  
Eyring Model ◽  
Eyring Theory ◽  
New Equation

A new Reynolds equation, based on the Eyring theory of non-Newtonian flow, is derived for flow in one dimension. It is shown that this new equation reduces to the traditional Reynolds equation as the Eyring model approaches the Newtonian model in the limit. Numerical solutions are presented for a selected oil at two different temperatures. The central film thickness decreases with increasing dimensionless viscosity parameter and slide/roll ratios. A transition zone is noted through which the ratio of minimum to central film thickness passes as the pressure distribution goes from near Hertzian to a distribution that appreciably deviates from Hertzian.

Waviness Amplitude Reduction in EHL Line Contacts Under Rolling-Sliding

1998 ◽  
Vol 120 (4) ◽  
pp. 705-709 ◽  
Author(s):  
A. A. Lubrecht ◽  
D. Graille ◽  
C. H. Venner ◽  
J. A. Greenwood
Keyword(s):  
Film Thickness ◽  
Financial Constraints ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
The Other ◽  
Foreseeable Future ◽  
Lubricant Film Thickness ◽  
Detailed Understanding ◽  
Line Contacts ◽  
Do So

Due to technological pressures the lubricant film thickness in EHD contacts has decreased over the years and will continue to do so for the foreseeable future. On the other hand, financial constraints cause the surface roughness in these contacts to decrease very slowly, or might even cause an increase. As a result, the ratio of film thickness to composite roughness will continue to decrease. The question that remains to be answered is to what extent this decrease will affect the contact performance. A third development makes this question even more acute, the request of increased reliability. As a consequence, the problem of the detailed understanding of the elastohydrodynamic lubrication with rough surfaces is as urgent as ever. Recent work has shown that the features inside the contact deform, and that the level of deformation is a function of the wavelength of the feature and the contact operating conditions, including slip. This last aspect of the problem, which has not been addressed previously, forms the central topic of the current paper. Instead of studying the deformation of a real roughness profile, the deformation of its sinusoidal Fourier components is investigated.

Darwin's two competing phylogenetic trees: marsupials as ancestors or sister taxa?

2012 ◽  
Vol 39 (2) ◽  
pp. 217-233 ◽  
Author(s):  
J. David Archibald
Keyword(s):  
Fossil Record ◽  
Evolutionary Biology ◽  
Phylogenetic Trees ◽  
Charles Darwin ◽  
The Other ◽  
Charles Lyell ◽  
Single Origin ◽  
Molecular Studies ◽  
Richard Owen ◽  
First Time

Studies of the origin and diversification of major groups of plants and animals are contentious topics in current evolutionary biology. This includes the study of the timing and relationships of the two major clades of extant mammals – marsupials and placentals. Molecular studies concerned with marsupial and placental origin and diversification can be at odds with the fossil record. Such studies are, however, not a recent phenomenon. Over 150 years ago Charles Darwin weighed two alternative views on the origin of marsupials and placentals. Less than a year after the publication of On the origin of species, Darwin outlined these in a letter to Charles Lyell dated 23 September 1860. The letter concluded with two competing phylogenetic diagrams. One showed marsupials as ancestral to both living marsupials and placentals, whereas the other showed a non-marsupial, non-placental as being ancestral to both living marsupials and placentals. These two diagrams are published here for the first time. These are the only such competing phylogenetic diagrams that Darwin is known to have produced. In addition to examining the question of mammalian origins in this letter and in other manuscript notes discussed here, Darwin confronted the broader issue as to whether major groups of animals had a single origin (monophyly) or were the result of “continuous creation” as advocated for some groups by Richard Owen. Charles Lyell had held similar views to those of Owen, but it is clear from correspondence with Darwin that he was beginning to accept the idea of monophyly of major groups.

Sphagnum mosses (Sphagnaceae, Bryophyta) of mires Chefandzar and Masota in North Ossetia (Caucasus)

2018 ◽  
Vol 52 (2) ◽  
pp. 455-462 ◽  
Author(s):  
G. Ya. Doroshina ◽  
I. A. Nikolajev
Keyword(s):  
Plant Communities ◽  
The Other ◽  
North Caucasus ◽  
Sphagnum Mosses ◽  
Greater Caucasus ◽  
The North ◽  
First Time ◽  
North Ossetia

Sphagnum mires on the Greater Caucasus are rare, characterized by the presence of relict plant communities of glacial age and are in a stage of degradation. The study of Sphagnum of Chefandzar and Masota mires is carried out for the first time. Seven species of Sphagnum are recorded. Their distribution and frequency within the North Caucasus are analyzed. Sphagnum contortum, S. platyphyllum, S. russowii, S. squarrosum are recorded for the first time for the study area and for the flora of North Ossetia. The other mosses found in the study area are listed.

An Epistemological Criticism of Social Entrepreneurship: Is Social Entrepreneurship a Sound Scientific Field of Research

2018 ◽  
Author(s):  
Amir Forouharfar
Keyword(s):  
Social Entrepreneurship ◽  
Social Constructivism ◽  
Social Epistemology ◽  
American English ◽  
Meta Analysis ◽  
Research Question ◽  
Knowledge Structure ◽  
Scientific Field ◽  
The Other ◽  
First Time

The paper was shaped around the pivotal question: Is SE a sound and scientific field of research? The question has given a critical tone to the paper and has also helped to bring out some of the controversial debates in the realm of SE. The paper was organized under five main discussions to be able to provide a scientific answer to the research question: (1)<b> </b>is “social entrepreneurship” an oxymoron?, (2) the characteristics of SE knowledge, (3) sources of social entrepreneurship knowledge, (4) SE knowledge: structure and limitations and (5) contributing epistemology-making concepts for SE.<b> </b>Based on the sections,<b> </b>the study relied on the relevant philosophical schools of thought in <i>Epistemology </i>(e.g. <i>Empiricism</i>, <i>Rationalism</i>, <i>Skepticism</i>, <i>Internalism</i> vs. <i>Externalism</i>,<i> Essentialism, Social Constructivism</i>, <i>Social Epistemology, etc.</i>) to discuss these controversies around SE and proposes some solutions by reviewing SE literature. Also, to determine the governing linguistic discourse in the realm of SE, which was necessary for our discussion,<i> Corpus of Contemporary American English (COCA)</i> for the first time in SE studies was used. Further, through the study, SE buzzwords which constitute SE terminology were derived and introduced to help us narrowing down and converging the thoughts in this field and demarking the epistemological boundaries of SE. The originality of the paper on one hand lies in its pioneering discussions on SE epistemology and on the other hand in paving the way for a construction of sound epistemology for SE; therefore in many cases after preparing the philosophical ground for the discussions, it went beyond the prevalent SE literature through meta-analysis to discuss the cases which were raised. The results of the study verified previously claimed embryonic pre-paradigmatic phase in SE which was far from a sound and scientific knowledge, although the scholarly endeavors are the harbingers of such a possibility in the future which calls for further mature academic discussion and development of SE knowledge by the SE academia.

A Nabatean port on the Red Sea: note on the pottery finds from al-Qusayr (al-Wajh, Saudi Arabia)

2020 ◽  
Author(s):  
Caroline Durand
Keyword(s):  
Saudi Arabia ◽  
19Th Century ◽  
Red Sea ◽  
Point Of View ◽  
The Other ◽  
Trade Routes ◽  
Other Hand ◽  
Roman Egypt ◽  
Pottery Sherds ◽  
First Time

Al-Qusayr is located 40 km south of modern al-Wajh, roughly 7 km from the eastern Red Sea shore. This site is known since the mid-19th century, when the explorer R. Burton described it for the first time, in particular the remains of a monumental building so-called al-Qasr. In March 2016, a new survey of the site was undertaken by the al-‘Ula–al-Wajh Survey Project. This survey focused not only on al-Qasr but also on the surrounding site corresponding to the ancient settlement. A surface collection of pottery sherds revealed a striking combination of Mediterranean and Egyptian imports on one hand, and of Nabataean productions on the other hand. This material is particularly homogeneous on the chronological point of view, suggesting a rather limited occupation period for the site. Attesting contacts between Mediterranean merchants, Roman Egypt and the Nabataean kingdom, these new data allow a complete reassessment of the importance of this locality in the Red Sea trade routes during antiquity.

Status of Family Fissidentaceae in Gujarat

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
D.G. Shah ◽  
D.N. Mehta ◽  
R.V. Gujar
Keyword(s):  
Distinct Species ◽  
The State ◽  
The Other ◽  
Land Plants ◽  
Reproductive Structures ◽  
The Family ◽  
The Status ◽  
Vegetative Characters ◽  
First Time ◽  
Different Parts

Bryophytes are the second largest group of land plants and are also known as the amphibians of the plant kingdom. 67 species of bryophytes have been reported from select locations across the state of Gujrat. The status of family fissidentaceae which is a large moss family is being presented in this paper. Globally the family consists of 10 genera but only one genus, Fissidens Hedw. has been collected from Gujarat. Fissidens is characterized by a unique leaf structure and shows the presence of three distinct lamina, the dorsal, the ventral and the vaginant lamina. A total of 8 species of Fissidens have been reported from the state based on vegetative characters as no sporophyte stages were collected earlier. Species reported from the neighboring states also showed the absence of sporophytes. The identification of different species was difficult due to substantial overlap in vegetative characters. Hence a detailed study on the diversity of members of Fissidentaceae in Gujarat was carried out between November 2013 and February 2015. In present study 8 distinct species of Fissidens have been collected from different parts of the state. Three species Fissidens splachnobryoides Broth., Fissidens zollingerii Mont. and Fissidens curvato-involutus Dixon. have been identified while the other five are still to be identified. Fissidens zollingerii Mont. and Fissidens xiphoides M. Fleisch., which have been reported as distinct species are actually synonyms according to TROPICOS database. The presence of sexual reproductive structures and sporophytes for several Fissidens species are also being reported for the first time from the state.

scholarly journals An augmented Lagrangian method for solving total variation (TV)-based image registration model

2020 ◽  
Vol 14 ◽  
pp. 174830262097353
Author(s):  
Noppadol Chumchob ◽  
Ke Chen
Keyword(s):  
Image Registration ◽  
Augmented Lagrangian ◽  
Numerical Solutions ◽  
Augmented Lagrangian Method ◽  
Closed Form Solution ◽  
Numerical Algorithms ◽  
Lagrangian Method ◽  
Form Solution ◽  
The Other ◽  
Other Hand

Variational methods for image registration basically involve a regularizer to ensure that the resulting well-posed problem admits a solution. Different choices of regularizers lead to different deformations. On one hand, the conventional regularizers, such as the elastic, diffusion and curvature regularizers, are able to generate globally smooth deformations and generally useful for many applications. On the other hand, these regularizers become poor in some applications where discontinuities or steep gradients in the deformations are required. As is well-known, the total (TV) variation regularizer is more appropriate to preserve discontinuities of the deformations. However, it is difficult in developing an efficient numerical method to ensure that numerical solutions satisfy this requirement because of the non-differentiability and non-linearity of the TV regularizer. In this work we focus on computational challenges arising in approximately solving TV-based image registration model. Motivated by many efficient numerical algorithms in image restoration, we propose to use augmented Lagrangian method (ALM). At each iteration, the computation of our ALM requires to solve two subproblems. On one hand for the first subproblem, it is impossible to obtain exact solution. On the other hand for the second subproblem, it has a closed-form solution. To this end, we propose an efficient nonlinear multigrid (NMG) method to obtain an approximate solution to the first subproblem. Numerical results on real medical images not only confirm that our proposed ALM is more computationally efficient than some existing methods, but also that the proposed ALM delivers the accurate registration results with the desired property of the constructed deformations in a reasonable number of iterations.

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