Rheological properties of liquids under conditions of elastohydrodynamic lubrication

There is an ongoing debate concerning the best rheological model for liquid flows in elastohydrodynamic lubrication (EHL). Due to the small contact area and high relative velocities of bounding solids, the lubricant experiences pressures in excess of 500 MPa and strain rates that are typically $10^5 -10^7$ $\textrm{s}^{-1}$. The high pressures lead to a dramatic rise in Newtonian viscosity $\eta_{N}$ and the high rates lead to large shear stresses and pronounced shear-thinning. This paper presents detailed simulations of a model EHL fluid, squalane, using nonequilibrium molecular dynamics methods to extract the scaling of its viscosity with shear rate ($10^5 - 10^{10}$ $\textrm{s}^{-1}$) over a wide range of pressure $P$ (0.1 MPa to 1.2 GPa), and temperature $T$ ($150 - 373$ K). Simulation results are consistent with a broad range of equilibrium and nonequilibrium experiments. At high $T$ and low $P$, where $\eta_{N}$ is low, the response can be fit to a power-law, as in the common Carreau model. Shear-thinning becomes steeper as $\eta_{N}$ increases, and for $\eta_{N}\gtrsim 1$ Pa-s, shear-thinning is consistent with the thermally activated flow assumed by another common model, Eyring theory. Simulations for a bi-disperse Lennard-Jones (LJ) system show that the transition from Carreau to Eyring is generic. For both squalane and the LJ system, the viscosity decreases by only about a decade in the Carreau regime, but may fall by many orders of magnitude in the Eyring regime. Shear thinning is often assumed to reflect changing molecular alignment, but the alignment of squalane molecules saturates after the viscosity has dropped by only about a factor of three. In contrast, thermal activation describes shear thinning by six or more decades in viscosity. Changes in the diagonal elements of the stress tensor with rate and shear stress are also studied.Comment: 17 pages, 18 figure

A Novel Coronavirus (nCOV- 2019): A Pandemic Severe Respiratory Tract Infections by SARS COV-2 in Human

Novel Coronavirus Disease 2019 (nCOV 2019) or Coronavirus is one which is associate communicable disease amongst variety of viruses that causes cold, fever, difficulty in breathing and ultimately death. The viruses cause metabolism infections, together with the mundane cold, that square measure usually delicate, although a lot of occasional forms like respiratory illness caused by SARS-CoV-2, the illness is that the reason for the 2019–20 coronavirus irruption. It’s primarily unfolded between individuals by diminutive droplets from infected people once they breathe or cough. Individuals could have few symptoms or develop febrility, cough, and shortness of breath. Whereas Feb 2020, different countries together with European country Asian Countries enclosed within the list. Antiviral drugs being tested embrace antimalarial drug, the ribonucleic acid enzyme substance remdesivir, and triazavirin, Umifenovir (Arbidol) and darunavir were planned. Remdesivir and antimalarial drug effectively inhibit the coronavirus in vitro. Favilavir approved as experimental corona virus drug. The objective of this review article to provide basic knowledge & preliminary opinion and to provide an advice which can be proved as the best mantra for defeating nCOV. Thus this review aims to throw light to the new and exciting areas of Virology,  Replication  cycle of corona virus ,  sign & symptoms and diagnosis, Spreading of corona virus, Structural biology of corona virus, the ways of treatment with  alternative medicines  other than antiviral drugs,  and prevention in its early stage of COVID-19 , and also Current Research on Corona. Keywords: Coronavirus, 2019-nCOV2, 2019–20 coronavirus irruption, SARS, WHO, Public Health Emergency of International Concern (PHEIC), replication of corona virus