scholarly journals Deviations From Classical Hydrodynamic Theory in Highly Confined Planar Poiseuille Flow of a Polymer Solution

2017 ◽  
Vol 23 (3) ◽  
Author(s):  
Adrian Menzel ◽  
Peter Daivis ◽  
Billy Todd
Keyword(s):  
Polymer Solution ◽  
Poiseuille Flow ◽  
Hydrodynamic Theory ◽  
Classical Hydrodynamic

Lubrication at point contacts

1961 ◽  
Vol 261 (1307) ◽  
pp. 532-550 ◽  
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Single Point ◽  
Applied Pressure ◽  
Hydrodynamic Theory ◽  
Radius Of Curvature ◽  
Point Contacts ◽  
Wide Range ◽  
Electrical Capacity ◽  
Classical Hydrodynamic

Measurements have been made of the friction, electrical resistance, and electrical capacity between rotating steel cylinders with their axes mutually at right angles. The lubricant was a plain hydrocarbon mineral oil. Nominally the surfaces come together at a single point and the apparatus is designed to ensure that this condition is maintained even if the cylinders wear. It is shown that hydrodynamic lubrication exists over a wide range of conditions. At loads of a few kilograms it persists even when the speed falls below 1 cm/s and at higher speeds (~ 100 cm/s) it is maintained even when the load becomes large enough to cause bulk plastic flow of hardened steel. Hitherto it has been considered that only boundary lubrication could occur under these extreme conditions. At very light loads classical hydrodynamic theory applies but as the load is increased a departure from classical theory occurs because the viscosity of the oil increases under the applied pressure. At heavier loads the pressures become large enough to cause appreciable elastic deformation of the surfaces and a state of elasto-hydrodynamic lubrication is achieved. Under elasto-hydrodynamic conditions the film thickness can be deduced from the measure­ments of electrical capacity. A simplified theory of elasto-hydrodynamic lubrication at point contacts is developed, and the measured values of film thickness are in fairly good agreement with those derived from the theory. However, the variations of film thick­ness with viscosity, speed and radius of curvature forecast by the theory differ significantly from those obtained experimentally. The values of the film thickness range from 2 x 10 -6 cm to more than 1 x 10 -4 cm. The results, over the whole range, conform to a regular pattern and there is no evidence of any disturbing influence of the surface molecular fields, even with the thinnest films.

scholarly journals Cross-stream migration of a Brownian droplet in a polymer solution under Poiseuille flow

Soft Matter ◽  
2019 ◽  
Vol 15 (15) ◽  
pp. 3168-3178 ◽  
Author(s):  
Michael P. Howard ◽  
Thomas M. Truskett ◽  
Arash Nikoubashman
Keyword(s):  
Polymer Solution ◽  
Poiseuille Flow ◽  
Polymer Solutions ◽  
Dilute Polymer Solutions ◽  
Stream Migration ◽  
Pressure Driven Flow ◽  
Pressure Driven

Dilute polymer solutions under pressure-driven flow can drive cross-stream migration of a small Brownian droplet to the centerline of a planar microchannel.

Thermohydrodynamic Phenomena in Fluid Film Lubrication

1973 ◽  
Vol 95 (2) ◽  
pp. 187-194 ◽  
Author(s):  
A. Seireg ◽  
H. Ezzat
Keyword(s):  
Reynolds Equation ◽  
Fluid Film ◽  
Hydrodynamic Theory ◽  
Load Carrying Capacity ◽  
Isothermal Conditions ◽  
Empirical Procedure ◽  
Load Carrying ◽  
Film Lubrication ◽  
Classical Hydrodynamic ◽  
Fluid Film Lubrication

The classical hydrodynamic theory of fluid film lubrication as described by Reynolds’ equation assumes isothermal conditions in the film. Such conditions may never exist in many engineering applications. A common practice is to calculate bearing performance with isothermal conditions at an average film temperature. This paper presents results on the load-carrying capacity of the film when thermal homogeneity does not exist. An empirical procedure is proposed for the prediction of the thermohydrodynamic behavior of the film. A hysteresis-type phenomenon in the pressure-temperature relationship is also observed.

Modelling of mixed hydrodynamic and boundary lubrication: Layered structures and shear thinning

1998 ◽  
Vol 212 (3) ◽  
pp. 171-177 ◽  
Author(s):  
S Jang ◽  
J. A. Tichy
Keyword(s):  
Boundary Lubrication ◽  
Hydrodynamic Lubrication ◽  
Shear Thinning ◽  
Hydrodynamic Theory ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Newtonian Case ◽  
Lubrication Conditions ◽  
Thinning Effect ◽  
Classical Hydrodynamic

This paper is concerned with an intermediate regime between boundary and hydrodynamic lubrication. With high molecular weight polymer lubricants, it is accepted that polymeric molecules stick to the boundary surfaces in the form of immobile solid-like layers whose thickness may be of the order of 50 nm. Such layers may comprise about half of the minimum film thickness under severe sliding conditions. In addition, shear thinning may occur in a central region of the film, away from the thickened layers. From this physical picture, a modified Reynolds equation is developed which depicts an immobile layer model representing molecular microstrucrure and a shear thinning effect away from the surface. Compared to the Newtonian case, the molecular microstructure causes much higher pressure levels. This result is consistent with the physical idea that slow sliding speeds can apparently generate sufficient forces to separate surfaces in boundary lubrication conditions, although the classical hydrodynamic theory would predict otherwise.

Surface waves on liquid helium-4

1971 ◽  
Vol 322 (1550) ◽  
pp. 355-359 ◽  
Keyword(s):  
Surface Tension ◽  
Surface Waves ◽  
Liquid Helium ◽  
Hydrodynamic Theory ◽  
Saturated Vapour ◽  
Helium 4 ◽  
Lambda Point ◽  
Two Fluid ◽  
Classical Hydrodynamic

The velocity of surface waves at the interface between 4 He and its saturated vapour has been determined over a range of temperatures both in the gravitational and surface tension region of frequencies. The results are compared with classical hydrodynamic theory and no two fluid effects below the lambda point are found.

A Critical Re-Evaluation of Hydrodynamic Theories and Experiments in Subcavitating Hydrofoil Flutter

1966 ◽  
Vol 10 (02) ◽  
pp. 122-132
Author(s):  
Wen-Hwa Chu
Keyword(s):  
Wind Tunnel ◽  
Experimental Research ◽  
Hydrodynamic Theory ◽  
Force Measurements ◽  
Surface Theory ◽  
Towing Tank ◽  
Force Calculation ◽  
Possible Cause ◽  
Theory And Experiments ◽  
Classical Hydrodynamic

A review of relevant hydrodynamic information has been made, with emphasis on the possible cause of serious discrepancies between classical hydrodynamic theory and experiments for subcavitating hydrofoils. The usefulness of the best available wind tunnel and towing tank force measurements is also discussed. It is believed that these data are unreliable, and that the completion of the force calculation based on the classical lifting surface theory and subsequent flutter prediction for an actual flutter model is desirable. Some recommendations for possible future experimental research are also given.

scholarly journals Multiscale Mixed Hydrodynamics in Line Contacts

2021 ◽  
Author(s):  
Yongbin Zhang
Keyword(s):  
Boundary Layer ◽  
Solid Surface ◽  
Fluid Model ◽  
Adsorbed Layer ◽  
Rolling Speed ◽  
Hertzian Contact ◽  
Hydrodynamic Theory ◽  
Flow Equations ◽  
Surface Separation ◽  
Classical Hydrodynamic

Abstract In the hydrodynamic line contact, there is a very thin layer physically adsorbed to the solid surface. When the surface separation is sufficiently small, the Hertzian contact zone will be completely filled with the boundary layer, while in most of the inlet zone still occurs continuum hydrodynamics, which lies between the mated adsorbed layers. The present paper studies this mixed hydrodynamics by a multiscale analysis. The boundary layer flows are simulated from the flow factor approach model; The intermediate continuum fluid flow is simulated from the continuum fluid model. The flow equations are given respectively for the boundary layers and for the intermediate continuum fluid. The final governing equation has been obtained relating the surface separation to the solid surface speeds and the carried load. The calculation results show that for a high rolling speed the hydrodynamic behavior in the contact agrees with the classical hydrodynamic theory; However for a critically low rolling speed it gives the surface separation greatly higher than that calculated from the classical hydrodynamic theory, showing the significant adsorbed layer effect.

scholarly journals PROBLEMS OF NONSTATIONARY FILTRATION

2018 ◽  
Vol 14 (1) ◽  
pp. 171-177
Author(s):  
Vsevolod A. Shabanov
Keyword(s):  
Classical Model ◽  
Equations Of Motion ◽  
Unsteady Motion ◽  
Hydrodynamic Theory ◽  
Filtration Theory ◽  
Machine Experiment ◽  
Special Cases ◽  
Theoretical Mechanics ◽  
Theory Of Filtration ◽  
Classical Hydrodynamic

he article deals with the classical hydrodynamic theory of filtration. Discusses models of soil, fluid and nature of fluid flow that formed the basis for the creation of the classic filtration theory. Also discusses the assumptions made for the linearization of the equations. Evaluated the scope of the classical filtration theory. Proposed a new model of filtration through a porous medium, based on the application of the laws of theoretical mechanics. It is based on the classical model of soil: the soil is composed of capillaries with ..parallel axes, in which the liquid moves. For tasks of infiltration equations of motion. Considered special cases of unsteady motion of a finite volume of liquid. Numerical example a machine experiment.

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