scholarly journals A new empirical correlating equation for calculating effective viscosity of nanofluids

2019 ◽  
Vol 48 (5) ◽  
pp. 1547-1562 ◽  
Author(s):  
Maher Dhahri ◽  
Hana Aouinet ◽  
Habib sammouda
Keyword(s):  
Effective Viscosity ◽  
Correlating Equation

Effects of Sonication Time on the Stability and Viscosity of Functionalized MWCNT-Based Nanolubricants

2020 ◽  
Vol 16 (4) ◽  
pp. 639-654
Author(s):  
Ahmet Selim Dalkilic ◽  
Bedri Onur Küçükyıldırım ◽  
Ayşegül Akdoğan Eker ◽  
Faruk Yıldız ◽  
Altuğ Akpinar ◽  
...  
Keyword(s):  
Effective Viscosity ◽  
Mass Concentration ◽  
Measured Data ◽  
Sonication Time ◽  
Empirical Correlations ◽  
Thermal Systems ◽  
The Stability ◽  
Rotary Viscometer ◽  
Functionalized Mwcnts ◽  
Measured Viscosity

Background: Active scholars in the nanofluid field have continuously attempted to remove the associated challenge of the stability of nanofluids via various approaches, such as functionalization and adding a surfactant. After preparing a stable nanofluid, one must measure the properties, as this is vital in the design of thermal systems. Objective: Authors aimed to investigate the stability and viscosity of refrigeration lubrication oilbased nanofluids containing functionalized MWCNTs. The effects of concentration and temperature on viscosity were studied. Furthermore, the present study focused on the effect of sonication time on the stability and viscosity of the prepared samples. Methods: After the preparation of chemically functionalized MWCNTs, solutions were dispersed with an ultrasonic homogenizer for 2, 4 and 8 hours sonication at maximum power. Viscosity measurements for all samples were made 10 minutes after sonication by adjusting the proper spinning velocity using a digital rotary viscometer. Results: The first part deals with the stability of the nanofluid as a nanolubricant, and the second one investigates the viscosity of the nanofluid and the effects of various parameters on it. The last one is related to the validation of the measured viscosity values by means of well-known empirical correlations. The measured data are given for validation issues. Conclusion: The samples will have higher stability by increasing the time of sonication. The viscosity of a nanofluid does not change with the increase of sonication time to two hours and higher. Up to mass concentration of 0.1%, the effective viscosity increases with adding nanotubes linearly.

A general model for the effective viscosity of pseudoplastic and dilatant fluids

1975 ◽  
Vol 14 (5) ◽  
pp. 404-409 ◽  
Author(s):  
St. W. Churchill ◽  
R. U. Churchill
Keyword(s):  
General Model ◽  
Effective Viscosity

scholarly journals Effective viscosity of a random mixture of fluids

2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Benoît Noetinger ◽  
Laurène Hume ◽  
Robin Chatelin ◽  
Philippe Poncet
Keyword(s):  
Effective Viscosity ◽  
Random Mixture

Dispersion Flow in Microchannels

2012 ◽  
Author(s):  
Alfir T. Akhmetov ◽  
Marat V. Mavletov ◽  
Sergey P. Sametov ◽  
Artur A. Rakhimov ◽  
Azat A. Valiev ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Effective Viscosity ◽  
Complex Structure ◽  
Experimental Investigations ◽  
Dispersed Phase ◽  
Rheological Characteristics ◽  
Dense Structure ◽  
The Third ◽  
Dynamic Blocking ◽  
Oil Emulsions

The work is devoted to experimental investigations of the features of flow of dispersions in microchannels. The paper consists of three parts. In the first part the flow of emulsions in smooth contracting cylindrical microchannels is investigated. It is received that a significant role at dynamic blocking of channels is played by the inclusions comparable by size to the diameter of a narrowing. This is in spite of the fact that their influence on the change of a flow rate of emulsion before blocking is insignificant. In the second part the generation of emulsion in a complex structure of microchannels (micromodels) when water is displaced by composition of hydrocarbon with surfactants is investigated. The experimental dependences of the rheological characteristics of emulsions based on the composition of SAS and water at different concentrations of the aqueous phase can explain blocking of a porous structure by generated emulsion. In the third part a comparison of flow of water-in-oil emulsions with the suspension which was obtained by freezing the microdroplets of the aqueous phase of emulsions was studied. It was found that the blocking of suspension is not as complete as in the case of emulsion. It is explained by deformation of the droplets and by formation of a dense structure, as opposed to suspension of beads, through which hydrocarbon phase is filtered. A small increase in effective viscosity due to solidification of freezing droplets of the dispersed phase was found.

Transient rheological behavior of blood in low-shear tube flow: velocity profiles and effective viscosity

1995 ◽  
Vol 268 (1) ◽  
pp. H25-H32 ◽  
Author(s):  
C. Alonso ◽  
A. R. Pries ◽  
O. Kiesslich ◽  
D. Lerche ◽  
P. Gaehtgens
Keyword(s):  
Effective Viscosity ◽  
Velocity Profiles ◽  
Low Flow ◽  
Cross Sectional ◽  
Video Recordings ◽  
Horizontal Tubes ◽  
Rbc Aggregation ◽  
Glass Tubes ◽  
Vertical Tubes ◽  
Low Shear

Velocity profiles of human blood flowing through vertical and horizontal glass tubes (25–100 microns ID) were measured as a function of time following a sudden reduction of wall shear stress (tau w) from a high value to values ranging from 2 to 100 mPa. Cell velocities at various radial positions were determined off-line from video recordings by digital image analysis. In vertical tubes, symmetric velocity profiles were obtained that developed increasing bluntness with time, particularly at lower tau w and in smaller tubes. In horizontal tubes, velocity profiles developed strong asymmetry as a function of time. Red blood cell (RBC) sedimentation was associated with uniform low flow velocities in the concentrating cell sediment, whereas faster flow and almost parabolic profiles were observed in the supernatant plasma region. Calculations of effective blood viscosity showed a decrease with time at low tau w in vertical tubes but an increase in horizontal tubes. The differences between profile shape and effective viscosity in vertical and horizontal tubes disappeared at tau w > 50 mPa. These findings are related to the cross-sectional distribution of RBC, which depends on RBC aggregation and sedimentation.

Mixing in Symmetric Holmboe Waves

2007 ◽  
Vol 37 (6) ◽  
pp. 1566-1583 ◽  
Author(s):  
W. D. Smyth ◽  
J. R. Carpenter ◽  
G. A. Lawrence
Keyword(s):  
Shear Layer ◽  
Effective Viscosity ◽  
Laboratory Experiments ◽  
Density Difference ◽  
Transition To Turbulence ◽  
Mixing Efficiency ◽  
Effective Diffusivities ◽  
Key Parameter

Abstract Direct simulations are used to study turbulence and mixing in Holmboe waves. Previous results showing that mixing in Holmboe waves is comparable to that found in the better-known Kelvin–Helmholtz (KH) billows are extended to cover a range of stratification levels. Mixing efficiency is discussed in detail, as are effective diffusivities of buoyancy and momentum. Entrainment rates are compared with results from laboratory experiments. The results suggest that the ratio of the thicknesses of the shear layer and the stratified layer is a key parameter controlling mixing. With that ratio held constant, KH billows mix more rapidly than do Holmboe waves. Among Holmboe waves, mixing increases with increasing density difference, despite the fact that the transition to turbulence is delayed or prevented entirely by the stratification. Results are summarized in parameterizations of the effective viscosity and diffusivity of Holmboe waves.

scholarly journals A numerical study of glacier advance over deforming till

2010 ◽  
Vol 4 (3) ◽  
pp. 359-372 ◽  
Author(s):  
G. J.-M. C. Leysinger Vieli ◽  
G. H. Gudmundsson
Keyword(s):  
Effective Viscosity ◽  
Numerical Study ◽  
Thickness Distribution ◽  
Plug Flow ◽  
Linear Wave ◽  
Sediment Layer ◽  
Mixed Flow ◽  
Model Experiments ◽  
Non Linear ◽  
Glacier Advance

Abstract. The advance of a glacier over a deforming sediment layer is analysed numerically. We treat this problem as a contact problem involving two slowly-deforming viscous bodies. The surface evolution of the two bodies, and of the contact interface between them, is followed through time. Using various different non-linear till rheologies, we show how the mode of advance depends on the relative effective viscosities of ice and till. Three modes of advances are observed: (1) overriding, where the glacier advances through ice deformation only and without deforming the sediment; (2) plug-flow, where the sediment is strongly deformed, the ice moves forward as a block and a bulge is built in front of the glacier; and (3) mixed-flow, where the glacier advances through both ice and sediment deformation. For the cases of both overriding and mixed-flow, an inverse depth-age relationship within the ice is obtained. A series of model experiments show the contrast in effective viscosity between ice and till to be the single most important model parameter defining the mode of advance and the resulting thickness distribution of the till. Our model experiments indicate that the thickness of the deforming till layer is greatest close to the glacier front. Measurements of till thickness taken in such locations may not be representative of deforming till thickness elsewhere. Given sufficiently large contrast in effective viscosity between ice and till, a sediment bulge is formed in front of the glacier. During glacier advance, the bulge quickly reaches a steady state form strongly resembling single-crested push moraines. Inspection of particle paths within the sediment bulge, shows that particles within the till travel at a different speed from the bulge itself, and the push moraine to advance as a form-conserving non-linear wave.

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