Interplay between bulk and molecular viscosity of a soft glassy nematic gel

2021 ◽  
pp. 1-11
Author(s):  
S. Vimala ◽  
Geetha G. Nair
Keyword(s):  
Molecular Viscosity

Molecular viscosity and diffusivity effects in transitional and shock-driven mixing flows

2021 ◽  
Vol 103 (1) ◽  
Author(s):  
F. S. Pereira ◽  
F. F. Grinstein ◽  
D. M. Israel ◽  
R. Rauenzahn
Keyword(s):  
Molecular Viscosity

Wave breaking in the presence of wind drift and swell

1974 ◽  
Vol 66 (4) ◽  
pp. 625-640 ◽  
Author(s):  
O. M. Phillips ◽  
M. L. Banner
Keyword(s):  
Wind Speed ◽  
Wave Breaking ◽  
Wind Wave ◽  
Maximum Amplitude ◽  
Velocity Difference ◽  
Wind Drift ◽  
Short Waves ◽  
Long Wave ◽  
Molecular Viscosity ◽  
Surface Drift

Wind, blowing over a water surface, induces a thin layer of high vorticity in which the wind stress is supported by molecular viscosity; the magnitude of the surface drift, the velocity difference across the layer, being of the order of 3% of the wind speed. When long waves move across the surface, there is a nonlinear augmentation of the surface drift near the long-wave crests, so that short waves, superimposed on the longer ones, experience an augmented drift in these regions. This is shown to reduce the maximum amplitude that the short waves can attain when they are at the point of incipient breaking.Theoretical estimates of the reduction are compared with measurements in wind-wave tanks by the authors and by Mitsuyasu (1966) in which long mechanically generated waves are superimposed on short wind-generated waves. The reductions measured in the energy density of the short waves by increasing the slope of the longer ones at constant wind speed are generally consistent with the predictions of the theory in a variety of cases.

Predictions of Momentum Transfer Between Rotating Cylinders: The Narrow Gap Problem

1972 ◽  
Vol 39 (1) ◽  
pp. 33-35 ◽  
Author(s):  
I. Catton ◽  
P. Ayyaswamy
Keyword(s):  
Momentum Transfer ◽  
Taylor Number ◽  
Rotating Cylinders ◽  
Comparison With Experiment ◽  
Number Comparison ◽  
Wide Range ◽  
Secondary Motion ◽  
Marginal State ◽  
Range Of Values ◽  
Molecular Viscosity

The contributions to momentum transfer by secondary motion, which arises beyond the marginal state of stability in a layer of fluid confined between rotating cylinders is calculated by an integral method. The procedure invokes the “shape assumption” due to Stuart. Results are presented in terms of an effective viscosity to molecular viscosity ratio that is a function of Taylor number. Comparison with experiment is found to be excellent over a wide range of values of the Taylor number (up to 1000 times the critical value).

scholarly journals Molecular Viscosity Sensors with Two Rotators for Optimizing the Fluorescence Intensity-Contrast Trade-off

2017 ◽  
Vol 24 (12) ◽  
pp. 2794-2794
Author(s):  
Seung-Chul Lee ◽  
Chang-Lyoul Lee ◽  
Jeongyun Heo ◽  
Chan-Uk Jeong ◽  
Gyeong-Hui Lee ◽  
...  
Keyword(s):  
Fluorescence Intensity ◽  
Trade Off ◽  
Viscosity Sensors ◽  
Molecular Viscosity ◽  
Intensity Contrast

Investigation of Inverse-Turbulent-Prandtl Number with Four RNG k-ε Turbulence Models on Compressor Discharge Pipe of Bioenergy Micro Gas Turbine

2016 ◽  
Vol 819 ◽  
pp. 392-400 ◽  
Author(s):  
Ahmad Indra Siswantara ◽  
Budiarso ◽  
Steven Darmawan
Keyword(s):  
Prandtl Number ◽  
Turbulence Model ◽  
Large Scale ◽  
Swirling Flow ◽  
Turbulent Viscosity ◽  
Turbulence Models ◽  
Small Scale ◽  
Turbulent Prandtl Number ◽  
Curved Pipe ◽  
Molecular Viscosity

Inverse-Turbulent Prandtl number (α) is an important parameter in RNG k-ε turbulence models since it affects the ratio of molecular viscosity and turbulent viscosity. In curved pipe, this highly affects the model prediction to a large range eddy-scale flow. According to Yakhot & Orzag, the α range from 1-1.3929 has not been investigated in detail in curved pipe flow (Yakhot & Orszag, 1986) and specific Re. This paper varied inverse-turbulent Prandtl number α to 1-1.3 in RNG k-ε turbulence model on cylindrical curved pipe in order to obtain the optimum value of α to predict unfully-developed flow in the curve with curve ratio R/D of 1.607. Analysis was conducted numericaly with inlet specified Re of 40900 which was generated from the experiment at α 1, 1.1, 1.2, 1.3. Wall surface roughness is not considered in this paper. With assumption that thermal diffusivity is always dominant to turbulent viscosity, higher Inverse-turbulent Prandtl number represent domination of turbulent viscosity to molecular viscosity of the flow and predict to have more interaction between large scale eddy to small scale eddy as well. The results show the use of α = 1.3 has increased the turbulent kinetic energy by 7% and the turbulent dissipation by 5% compared to general inverse-turbulent Prandtl number of 1. The value difference shows that the use of higher α on RNG turbulence model described more interaction between eddies in secondary and swirling flow at pipe curve at Re = 40900.

scholarly journals Large-scale instability of a generalized turbulent Kolmogorov flow

2009 ◽  
Vol 16 (4) ◽  
pp. 569-577 ◽  
Author(s):  
B. Legras ◽  
B. Villone
Keyword(s):  
Turbulent Flows ◽  
Mirror Symmetry ◽  
Large Scale ◽  
Necessary Condition ◽  
Scale Separation ◽  
Kolmogorov Flow ◽  
Nonlinear Contribution ◽  
Basic Scale ◽  
Negative Viscosity ◽  
Molecular Viscosity

Abstract. We present an analytical study of the large scale instability of a generalized turbulent Kolmogorov flow, i.e. a periodic shear flow where the molecular viscosity has been substituted by an eddy viscosity parameterized with the Clark-Smagorinsky model and where the external forcing is adapted to maintain the flow against this dissipation. We employ multiscaling technique assuming a scale separation between the basic scale of such a generalized turbulent Kolmogorov flow and the largest scales of the flow. The main result is that an amplitude equation for the large-scale secondary flow is obtained which exhibits, like for the standard Kolmogorov flow, an instability of the negative viscosity type. We find that the presence of mirror symmetry in the basic flow is a necessary condition and that further propagative and nonlinear contribution are produced otherwise. The result is encouraging for the generic existence of large-scale instabilities of the negative viscosity type in fully turbulent flows.

Assessment Measures for LES Applications

2006 ◽  
Author(s):  
I. Celik ◽  
M. Klein ◽  
J. Janicka
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Power Spectra ◽  
Grid Size ◽  
Large Eddy Simulations ◽  
Large Eddy ◽  
Modeling Errors ◽  
The Common ◽  
Assessment Measures ◽  
Molecular Viscosity

Anticipating that Large Eddy Simulations will increasingly become the future engineering tool for research, development and design, it is deemed necessary to formulate some quality assessment measures that can be used to judge the resolution of turbulent scales and the accuracy of predictions. In this context some new and refined measures are proposed above and beyond those already published by the authors in the common literature. These new measures involve (a) fraction of total turbulent kinetic energy, (b) relative grid size with respect to Kolmogorov or Taylor scales, (c) relative effective sub-grid/numerical viscosity with respect to molecular viscosity, and (d) some property related to power spectra of turbulent kinetic energy. In addition, an attempt is made to segregate the contributions from numerical and modeling errors. Proposed measures are applied to various benchmark cases, and validated against fully resolved LES and/or DNS whenever possible. Along the same line of thinking, the authors present a perspective for verification of under-resolved direct numerical simulations.

Reply to comment by V.N. Zharkov "On estimating the molecular viscosity of the Earth's outer core"

2009 ◽  
Vol 179 (1) ◽  
pp. 108 ◽  
Author(s):  
D.E. Smylie ◽  
Vadim V. Brazhkin ◽  
A. Palmer
Keyword(s):  
Outer Core ◽  
Molecular Viscosity

A Calculation Method for Incompressible Viscous, Blade-to-Blade Flow through Radial Turbomachines with Log-Spiral Blade Surfaces

1979 ◽  
Vol 101 (3) ◽  
pp. 450-458 ◽  
Author(s):  
C. Bosman ◽  
K. C. Chan ◽  
A. P. Hatton
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Boundary Conditions ◽  
Difference Method ◽  
Calculation Method ◽  
Stress System ◽  
Slip Model ◽  
Spiral Blade ◽  
Flow Through ◽  
Molecular Viscosity

A finite difference method of blade-to-blade calculation for incompressible turbulent, viscous flow through radial turbomachines having log-spiral blades lying entirely in the r-θ plane is presented. A Newtonian stress system is incorporated into the calculation which employs a slip model for flow close to the blade surfaces. The effects of turbulence are simulated by use of an enhanced molecular viscosity. This problem is of a higher mathematical order than the usual free slip, inviscid calculation commonly applied in the design and analysis of these machines and raises interesting considerations of understanding with respect to mathematical closure and boundary conditions. Experimental results for flow through an actual machine of similar geometry to that analyzed are available and comparison of streamlines and velocity profiles are made.

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