Flow electrification phenomenon for newtonian and non-newtonian liquids: influence of liquid conductivity, viscosity and shear stress

2014 ◽  
Vol 21 (2) ◽  
pp. 693-703 ◽  
Author(s):  
M. S. Vihacencu ◽  
P. V. Notingher ◽  
T. Paillat ◽  
S. Jarny
Author(s):  
Avinash Kumar ◽  
Subhra Datta ◽  
Dinesh Kalyanasundaram

Even Newtonian liquids are now known to slip past suitably engineered surfaces, such as those exhibiting super-hydrophobicity. Through friction reduction, such surfaces have potential to significantly reduce the required the motive power to drive confined flows. Studies of unconfined shear flows over such surfaces have revealed that patterned slipping surfaces are intrinsically inferior to the less realizable uniformly slipping surfaces in terms of the fluid slip velocity generated per unit pattern-averaged shear stress. In this study, a spectrally accurate semianalytical approach is used to assess the friction-reduction performance of several alternate ways of confining the flow over a patterned surface. Fluid permeates by pressure differential through a channel with plate-like walls. One of the plates forming the channel is kept fixed throughout the study to have a sinusoidal slip pattern, while the second plate can be non-slipping, uniformly slipping and patterned identically to the first surface. The gap between the plates, the degree of slip and pattern waveform parameters can be varied between limits not restricted by the model. Significantly different behaviours in permeability and the effective degree of slip of the first plate arise from the differences in patterning on the second plate.


2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Pedram Tazraei ◽  
Alireza Riasi

In this study, the difference between laminar fast transient flow of shear-thinning liquids and that of Newtonian liquids under similar conditions is numerically studied. Since the literature appears to lack fast transient flow investigation of non-Newtonian fluids, this work addresses features of those flows. In this way, the Newton–Kantorovich method is implemented to linearize nonlinear shear stress term available in the characteristic equations. The verification and validation of the solution are carried out in detail. The results show that the non-Newtonian behavior of fluids has significant influence on the velocity and shear stress profiles and also on the magnitude of pressure head and wall shear stress.


1969 ◽  
Vol 36 (3) ◽  
pp. 417-426 ◽  
Author(s):  
L. W. Phipps

SummaryThe dynamic viscosity coefficients η of creams containing up to 50% fat have been determined at temperatures of approximately 40, 50, 60, 70 and 80°C. All the creams behaved as Newtonian liquids, the shear stress being proportional to rate of shear up to the maximum rate used of 100 sec−1. At a given temperature a linear dependence of log η on (φ+φ5/3) was obtained for φ < 0·4, where φ is the concentration (w/w) of fat. Interpolation formulae have been derived to enable η to be calculated at any temperature between 40 and 80°C and for any fat content up to 40%. Formulae for the density ρ of cream have also been deduced to permit kinematic viscosities η/ρ to be computed. Nomograms have been constructed to enable η and ρ to be readily determined without the use of the interpolation formulae and when slight loss in accuracy is unimportant.


1998 ◽  
Vol 120 (2) ◽  
pp. 173-178 ◽  
Author(s):  
Scott Bair

Recent advances in high pressure rheometry have elucidated the shear response of liquid lubricants at the high shear stress characteristic of the traction generating region of lubricated concentrated contacts. These new measurement techniques are used to characterize the shear response of shear thinning liquids at low (<10 MPa) shear stress. A recently developed numerical scheme for calculating film thickness is extended to accommodate sliding. Film thickness predictions are compared with measurements using shear thinning liquids including a polymer/mineral oil blend, a highly elastic liquid, and synthetic base oils. Useful insights are provided concerning the effects of pressure-viscosity behavior for Newtonian liquids, sliding, and starvation for non-Newtonian liquids and the relevant shear stress for film forming.


1987 ◽  
Vol 52 (4) ◽  
pp. 913-928 ◽  
Author(s):  
Václav Sobolík ◽  
Ondřej Wein ◽  
Jan Čermák

The film thickness and wall shear stress were measured simultaneously by electrodiffusional and capacitance methods. Experimental data were confronted with the existing theories of gravity flow of non-Newtonian liquids in wavy films with free surface.


2020 ◽  
Vol 134 (17) ◽  
pp. 2399-2418
Author(s):  
Yoshito Yamashiro ◽  
Hiromi Yanagisawa

Abstract Blood vessels are constantly exposed to mechanical stimuli such as shear stress due to flow and pulsatile stretch. The extracellular matrix maintains the structural integrity of the vessel wall and coordinates with a dynamic mechanical environment to provide cues to initiate intracellular signaling pathway(s), thereby changing cellular behaviors and functions. However, the precise role of matrix–cell interactions involved in mechanotransduction during vascular homeostasis and disease development remains to be fully determined. In this review, we introduce hemodynamics forces in blood vessels and the initial sensors of mechanical stimuli, including cell–cell junctional molecules, G-protein-coupled receptors (GPCRs), multiple ion channels, and a variety of small GTPases. We then highlight the molecular mechanotransduction events in the vessel wall triggered by laminar shear stress (LSS) and disturbed shear stress (DSS) on vascular endothelial cells (ECs), and cyclic stretch in ECs and vascular smooth muscle cells (SMCs)—both of which activate several key transcription factors. Finally, we provide a recent overview of matrix–cell interactions and mechanotransduction centered on fibronectin in ECs and thrombospondin-1 in SMCs. The results of this review suggest that abnormal mechanical cues or altered responses to mechanical stimuli in EC and SMCs serve as the molecular basis of vascular diseases such as atherosclerosis, hypertension and aortic aneurysms. Collecting evidence and advancing knowledge on the mechanotransduction in the vessel wall can lead to a new direction of therapeutic interventions for vascular diseases.


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