Independence between friction and velocity distribution in fluids subjected to severe shearing and confinement

2018 ◽  
Vol 20 (43) ◽  
pp. 27280-27293 ◽  
Author(s):  
Alejandro Porras-Vazquez ◽  
Laetitia Martinie ◽  
Philippe Vergne ◽  
Nicolas Fillot
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
High Shear ◽  
Lubricant Thickness

Lubricated friction at high shear and high enough pressure becomes saturated, independently of the velocity profile in the lubricant thickness.

scholarly journals The Dynamics of the Amery Ice Shelf

1966 ◽  
Vol 6 (45) ◽  
pp. 335-358 ◽  
Author(s):  
W. Budd
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Power Flow ◽  
Stress Distributions ◽  
Ice Shelf ◽  
General Survey ◽  
Mass Budget ◽  
Preliminary Results ◽  
Amery Ice Shelf ◽  
Theoretical Considerations

A general survey of the preliminary results of a three-year program of measurements on the Amery Ice Shelf by A.N.A.R.E. are presented, together with theoretical considerations of the velocity and stress distributions and the mass and energy regimes of the ice shelf. In order to explain the observed velocity distribution it has been found necessary to extend Weertman’s theory of ice-shelf creep to an ice shelf bounded at its sides. The resulting theoretical velocity profile applied to the results of the Amery Ice Shelf provides estimates of the average values of the power flow-law parameters for the ice shelf. The energy and mass budget considerations, together with the recorded change in form of the ice front, suggest that the ice-shelf regime is not in a continual state of balance but may fluctuate as the ice shelf changes in form over a period of about forty years.

scholarly journals Analysis of the velocity distribution in different types of ventilation system ducts

2018 ◽  
Vol 180 ◽  
pp. 02081 ◽  
Author(s):  
Kazimierz Peszyński ◽  
Lukasz Olszewski ◽  
Emil Smyk ◽  
Daniel Perczyński
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Cross Section ◽  
Power Law ◽  
Flow Rate ◽  
Fundamental Problem ◽  
Ventilation System ◽  
Different Types ◽  
Actual Profile ◽  
Ventilation Duct

The paper presents the results obtained during the preliminary studies of circular and rectangular ducts before testing the properties elements (elbows, tees, etc.)of rectangular with rounded corners ducts. The fundamental problem of the studies was to determine the flow rate in the ventilation duct. Due to the size of the channel it was decided to determine the flow rate based on the integration of flow velocity over the considered cross-section. This method requires knowledge of the velocity distribution in the cross section. Approximation of the measured actual profile by the classic and modified Prandtl power-law velocity profile was analysed.

The Preliminary Study on Comparison of Velocity Distribution Models Under the Same Roughness Length

2006 ◽  
Author(s):  
Jialing Hao ◽  
Yixin Yan ◽  
Zhiyao Song ◽  
Changnan Wang
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Linear Model ◽  
Tidal Cycle ◽  
Roughness Length ◽  
Distribution Model ◽  
Surface Boundary ◽  
Distribution Models ◽  
Logarithmic Model ◽  
Log Linear

Previous studies pointed out that due to the acceleration or deceleration action of tide current, the flow structure deviates from traditional logarithmic law in estuary, coast or other near shore water. The tidal velocity distribution model was derived and compared with the traditional logarithmic model. It should be pointed out that the velocity data adopted have four layers within one meter above the bed, and the roughness length z0 is different in the two models even in the same velocity profile. Because the fluctuation of roughness length z0 is remarkable when determining by single velocity profile, some studies thought that the variation of roughness length was small between adjacent time when the change of topography was less obviously. Therefore, the measured data is divided into several sections by one day or a tidal cycle to fit the velocity profile of every section to obtain a roughness length z0, i.e., the roughness length z0 varies only after a day or a tidal cycle. The purpose of the paper is to expand the log-linear model to full depth by adding the surface boundary condition ∂u∂zz=D=0(Diswaterdepth) and to discuss the difference when 6 points (bottom layer, 0.2D, 0.4D, 0.6D, 0.8D, surface layer) velocity profile are fitted by logarithmic model, log-linear model, and extended log-linear model with the same roughness length z0 in different time section, respectively. The calculated friction velocity and friction coefficient and their correlation are discussed. The results show that the log-linear model and the log-linear extend model are closer to the measure velocity profile than that of the logarithmic model.

scholarly journals Featuresof velocity distribution in a turbulent flow

Vestnik MGSU ◽  
2015 ◽  
pp. 103-109
Author(s):  
Valeriy Stepanovich Borovkov ◽  
Valeriy Valentinovich Volshanik ◽  
Irina Aleksandrovna Rylova
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Drag Coefficient ◽  
Viscous Flow ◽  
Measured Velocity ◽  
Displacement Thickness ◽  
Logarithmic Velocity Profile

In this article the questions of kinematic structure of steady turbulent flow near a solid boundary are considered. It has been established that due to friction the value of the local Reynolds number decreases and always becomes smaller than the critical value of the Reynolds number, which leads to formation of viscous flow near a wall. Velocity profiles for the area of viscous flow with constant and variable shear stress are obtained. The experimental investigations of different authors showed that in this area the flow is of unsteady character, where viscous flow occurs intermittently with turbulent flow. With increasing distance from the wall the flow becomes fully turbulent. In the area where generation and dissipation of turbulence are very intensive, there is a developed turbulent flow with increasing distance from the wall. Dissipation of turbulence is an action of viscous force. The logarithmic velocity profile was obtained by L. Prandtl disregarding the viscous component and the linear variation of the shear stress in the depth flow. The profile parameters C and k were determined from Nikuradze’s experiments. The detailed investigations of Nikuradze’s experiments established the part of the flow where the logarithmic velocity profile is correctly confirmed.This part of the flow was called “Prandtl layer”. The measured velocity distribution above this layer deviates in the direction of greater values. Processing of experimental data revealed that the thickness of the “Prandtl layer”, normalized to the radius of a pipe, depend on a drag coefficient. The formula for determining the thickness of the “Prandtl layer” with the known value of the drag coefficient is obtained. It is shown that the thickness of “Prandtl layer” almost coincides with the boundary layer displacement thickness formed on the wall of the pipe.

scholarly journals Simulation of Snow Drift and the Effects of Snow Particles on Wind

2008 ◽  
Vol 2008 ◽  
pp. 1-6 ◽  
Author(s):  
Jie Zhang ◽  
Ning Huang
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Friction Velocity ◽  
Average Height ◽  
Infinite Plane ◽  
Coupled Equations ◽  
Snow Drift ◽  
Snow Particle ◽  
Particle Bed ◽  
Snow Transport

Coupled equations between wind and saltating particles are presented for a stable wind blowing over an infinite plane bed and the equations are solved for a simplified particle-bed impact process. The calculated results show that the saltating snow particles strongly affect the velocity distribution of the wind, causing a deviation from a logarithmically distributed wind velocity profile. The average height and length of saltating snow particle trajectories exponentially increase as the friction velocity increases; the ejected snow number flux and the streamwise snow transport rate also increase as the friction velocity increases.

Annular Flow—A Note on the Turbulent Velocity Profile

1958 ◽  
Vol 62 (575) ◽  
pp. 830-831 ◽  
Author(s):  
Henry Barrow
Keyword(s):  
Experimental Data ◽  
Velocity Profile ◽  
Velocity Distribution ◽  
Power Law ◽  
Annular Flow ◽  
Turbulent Velocity ◽  
Concentric Annulus ◽  
Annular Section ◽  
Modified Power Law

The Important characteristics of the turbulent velocity profile of a plain concentric annulus and some of the methods of correlating the velocity distribution are briefly reviewed. The average velocities in an annular section are examined and some experimental data is correlated by a modified power law.

Velocity Profile Effects on the Discharge Coefficient of Pressure-Differential Meters

1963 ◽  
Vol 85 (3) ◽  
pp. 338-342 ◽  
Author(s):  
A. G. Ferron
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Discharge Coefficient ◽  
Pressure Differential ◽  
Characteristic Manner

Tests performed on a high-differential meter, venturi meter, and orifice indicated changes in the discharge coefficient with changes in upstream velocity distribution. These tests along with those by other investigators lead to the conclusion that all pressure-differential meters are affected by upstream velocity distributions when defined in some characteristic manner. This effect is increased as the beta ratio increases.

scholarly journals The Dynamics of the Amery Ice Shelf

1966 ◽  
Vol 6 (45) ◽  
pp. 335-358 ◽  
Author(s):  
W. Budd
Keyword(s):  
Velocity Profile ◽  
Velocity Distribution ◽  
Power Flow ◽  
Stress Distributions ◽  
Ice Shelf ◽  
General Survey ◽  
Mass Budget ◽  
Preliminary Results ◽  
Amery Ice Shelf ◽  
Theoretical Considerations

A general survey of the preliminary results of a three-year program of measurements on the Amery Ice Shelf by A.N.A.R.E. are presented, together with theoretical considerations of the velocity and stress distributions and the mass and energy regimes of the ice shelf.In order to explain the observed velocity distribution it has been found necessary to extend Weertman’s theory of ice-shelf creep to an ice shelf bounded at its sides. The resulting theoretical velocity profile applied to the results of the Amery Ice Shelf provides estimates of the average values of the power flow-law parameters for the ice shelf.The energy and mass budget considerations, together with the recorded change in form of the ice front, suggest that the ice-shelf regime is not in a continual state of balance but may fluctuate as the ice shelf changes in form over a period of about forty years.

Velocity Profile Investigation of FFS Microchannel at Re 100

2014 ◽  
Vol 487 ◽  
pp. 290-293
Author(s):  
Vithyacharan Retnasamy ◽  
Zaliman Sauli ◽  
Steven Taniselass ◽  
Nor Shakirina Nadzri ◽  
Tan Hsio Mei ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Velocity Profile ◽  
Velocity Distribution ◽  
Cross Sections ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Step Height ◽  
Forward Facing Step

Recently, microfluidics system has been widely employed in various areas for instance biomedical,pharmaceuticals and cell biological researchdue to its advantages. The flow behavior in microchannels with different cross-sections has been topic in previous studies. In this paper, numerical simulation of fluid flow in Forward Facing Step (FFS) configuration was performed to investigate velocity profile after the step. Reynolds numbers (Re) 100 with different step heights, 1μm and 3μm were used to observe trend occurs in the flow characteristics. The result illustrated an increase of velocity distribution with the increase of the step height.

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