Dissipative Heating Effects and End Corrections for Viscous Newtonian Flow in High Shear Capillary Tube Viscometry

1975 ◽  
Vol 97 (3) ◽  
pp. 472-478 ◽  
Author(s):  
J. Jakobson ◽  
W. O. Winer
Keyword(s):  
Shear Stress ◽  
Apparent Viscosity ◽  
Capillary Tube ◽  
Dissipative Heating ◽  
High Shear ◽  
Flow Curves ◽  
Heating Effects ◽  
Order Of Magnitude ◽  
End Corrections ◽  
Newtonian Behavior

The effect of dissipation heating on the apparent viscosity measured in capillary tube viscometry is described in this paper. Conditions of low Reynolds number and high shear are assumed. End corrections to the tube flow, found to be 3π/16 times the diameter of the tube, are incorporated. The flow curves show decreasing apparent viscosity when the shear stress increases. The configuration of the flow curves plotted in logarithmic presentation are found to be identical for fluids with Newtonian behavior. Convection is the predominant mechanism in removal of the heat in short capillary tube. The estimated upper bound for the shear stress obtainable in short length capillary tubes appears to be of the order of magnitude of 10 MPa limited primarily by the pressure drop associated with the constant end correction from the flat ended inlet and exit of the tube.

High Shear Stress Behavior of Some Representative Lubricants

1975 ◽  
Vol 97 (3) ◽  
pp. 479-485 ◽  
Author(s):  
J. Jakobsen ◽  
W. O. Winer
Keyword(s):  
Shear Stress ◽  
Capillary Tube ◽  
Pressure Level ◽  
High Shear ◽  
Newtonian Viscosity ◽  
Constant Viscosity ◽  
Independent Behavior ◽  
End Corrections ◽  
Silicone Lubricant ◽  
Newtonian Behavior

Shear stress independent behavior was observed for representative, synthetic, nonblended lubricants to about 4.8 × 106 N/m2 (700 psi) shear stress in high pressure viscometric measurements. This shear stress is of the same magnitude as the shear stress in sliding elastohydrodynamic contacts. It is shown that dissipation heating is the only mechanism of importance in the generation of the deviations from constant viscosity as measured with capillary tube viscometric methods. The Newtonian end corrections for the capillary tubes were found to be constant for the nonblended, liquid lubricants. Newtonian behavior will be expected of the fluids in a high shear lubrication situation. Shear induced, nonliquid behavior was found for the silicone lubricant at about 106 N/m2 and for the polymer-blended mineral oil at about 104 N/m2 at a relatively low pressure level. The observations might provide a key to an understanding of the generation of the anomalous low elastohydrodynamic film thickness as found with these lubricants. The polymer-blended oil showed shear thinning effects. The apparent viscosity was found to increase (∼30 percent) with increasing shear stress in the range of the second Newtonian viscosity level.

scholarly journals Rheology of embryonic avian blood

2011 ◽  
Vol 301 (6) ◽  
pp. H2473-H2481 ◽  
Author(s):  
Sarah Al-Roubaie ◽  
Espen D. Jahnsen ◽  
Masud Mohammed ◽  
Caitlin Henderson-Toth ◽  
Elizabeth A. V. Jones
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Cardiovascular System ◽  
Blood Viscosity ◽  
Apparent Viscosity ◽  
Developmental Stages ◽  
Shear Rates ◽  
Stage Of Development ◽  
Avian Blood ◽  
Newtonian Behavior

Shear stress, a mechanical force created by blood flow, is known to affect the developing cardiovascular system. Shear stress is a function of both shear rate and viscosity. While established techniques for measuring shear rate in embryos have been developed, the viscosity of embryonic blood has never been known but always assumed to be like adult blood. Blood is a non-Newtonian fluid, where the relationship between shear rate and shear stress is nonlinear. In this work, we analyzed the non-Newtonian behavior of embryonic chicken blood using a microviscometer and present the apparent viscosity at different hematocrits, different shear rates, and at different stages during development from 4 days (Hamburger-Hamilton stage 22) to 8 days (about Hamburger-Hamilton stage 34) of incubation. We chose the chicken embryo since it has become a common animal model for studying hemodynamics in the developing cardiovascular system. We found that the hematocrit increases with the stage of development. The viscosity of embryonic avian blood in all developmental stages studied was shear rate dependent and behaved in a non-Newtonian manner similar to that of adult blood. The range of shear rates and hematocrits at which non-Newtonian behavior was observed is, however, outside the physiological range for the larger vessels of the embryo. Under low shear stress conditions, the spherical nucleated blood cells that make up embryonic blood formed into small aggregates of cells. We found that the apparent blood viscosity decreases at a given hematocrit during embryonic development, not due to changes in protein composition of the plasma but possibly due to the changes in cellular composition of embryonic blood. This decrease in apparent viscosity was only visible at high hematocrit. At physiological values of hematocrit, embryonic blood viscosity did not change significantly with the stage of development.

scholarly journals Mechanical force effect on the two-state equilibrium of the hyaluronan-binding domain of CD44 in cell rolling

2015 ◽  
Vol 112 (22) ◽  
pp. 6991-6996 ◽  
Author(s):  
Takashi Suzuki ◽  
Miho Suzuki ◽  
Shinji Ogino ◽  
Ryo Umemoto ◽  
Noritaka Nishida ◽  
...  
Keyword(s):  
Shear Stress ◽  
Conformational Change ◽  
Mechanical Force ◽  
Binding Domain ◽  
Terminal Region ◽  
Hematopoietic Progenitor Cell ◽  
High Shear ◽  
Cell Rolling ◽  
High Affinity ◽  
C Terminus

CD44 is the receptor for hyaluronan (HA) and mediates cell rolling under fluid shear stress. The HA-binding domain (HABD) of CD44 interconverts between a low-affinity, ordered (O) state and a high-affinity, partially disordered (PD) state, by the conformational change of the C-terminal region, which is connected to the plasma membrane. To examine the role of tensile force on CD44-mediated rolling, we used a cell-free rolling system, in which recombinant HABDs were attached to beads through a C-terminal or N-terminal tag. We found that the rolling behavior was stabilized only at high shear stress, when the HABD was attached through the C-terminal tag. In contrast, no difference was observed for the beads coated with HABD mutants that constitutively adopt either the O state or the PD state. Steered molecular dynamics simulations suggested that the force from the C terminus disrupts the interaction between the C-terminal region and the core of the domain, thus providing structural insights into how the mechanical force triggers the allosteric O-to-PD transition. Based on these results, we propose that the force applied from the C terminus enhances the HABD–HA interactions by inducing the conformational change to the high-affinity PD transition more rapidly, thereby enabling CD44 to mediate lymphocyte trafficking and hematopoietic progenitor cell homing under high-shear conditions.

Flow curves of mixtures of acrylonitrile–styrene copolymers with different molecular weights at extremely high shear rates (abstract)

1991 ◽  
Vol 35 (4) ◽  
pp. 706-706
Author(s):  
Hideroh Takahashi ◽  
Yoshinori Inoue ◽  
Satoru Yamamoto ◽  
Osami Kamigaito
Keyword(s):  
High Shear ◽  
Flow Curves ◽  
Shear Rates ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
High Shear Rates

Abstract 476: Shear Stress-induced Atherosclerotic Plaque Regression is Reversed by Regulation of Macrophage Mobility via Matrix Metalloproteinase Inhibition

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Stefania Simeone ◽  
Talin Ebrahimian ◽  
Veronique Michaud ◽  
Stephanie Lehoux
Keyword(s):  
Shear Stress ◽  
High Fat Diet ◽  
Fold Increase ◽  
Atherosclerotic Plaques ◽  
High Shear ◽  
High Fat ◽  
Gelatinase Activity ◽  
Mmp Inhibitor ◽  
Post Surgery ◽  
Plaque Regression

Atherosclerotic plaques form in regions of low blood flow, whereas vessels exposed to high shear stress remain lesion-free. We hypothesized that exposing established atherosclerotic plaques to elevated shear stress leads to lesion regression by facilitating inflammatory cell movement within the plaque. We developed a model of arteriovenous fistula (AVF) in mice, where the right carotid artery is anastomosed into the jugular vein. LDLR-/- mice were placed on a high-fat diet. Control mice were sacrificed at week 12, which coincided with sham and AVF surgery. Sham and AVF mice were kept on a high-fat diet for a further 4 weeks. This procedure increases the shear stress in the brachiocephalic artery (BCA) and leads to a 51% plaque regression in AVF. All groups had comparable lipid levels. However, BCA plaque macrophage, smooth muscle cell and collagen content was halved in AVF. We observed greater gelatinase activity in plaques of AVF mice, suggesting a role for matrix metalloproteinases (MMPs) in plaque regression. MMP-9 and MMP-3 expression was increased in AVF plaques whereas MMP-2 and MMP-14 expression was decreased (p<0.05). A separate group of mice was therefore treated post-surgery with an MMP inhibitor, doxycycline, or with a TIMP-1 over-expressing plasmid. Both prevented the reduction in plaque size in the AVF group. To better define the mechanism of plaque regression in the AVF, we devised an endothelial cell (EC)-macrophage co-culture system where the ECs were exposed to high, low or no shear stress, and macrophages exposed to the EC effluent. There was a 2.5 fold increase in the migration of macrophages exposed to high shear effluent vs. low shear (p<0.05). This coincided with a 3-fold increase in the number of macrophages expressing activated β1 integrin in the high shear conditions. Uptake of apoptotic cells by macrophages was also 25% higher in the high shear vs. static (p<0.05). When repeated using the MMP inhibitor, GM6001, the high shear increase in migration was blocked in the presence of MMP inhibition; however, it had no effect on cell phagocytosis. Our findings suggest that shear stress acting on ECs may influence the cells within the plaque by increasing MMP activity allowing for better macrophage motility, an important feature of regressing plaques.

scholarly journals 5065Platelet desialylation induced by high shear-stress mechanical circulatory support

2018 ◽  
Vol 39 (suppl_1) ◽  
Author(s):  
H Spillemaeker ◽  
A Dupont ◽  
A Kauskot ◽  
A Rauch ◽  
F Vincent ◽  
...  
Keyword(s):  
Shear Stress ◽  
Mechanical Circulatory Support ◽  
Circulatory Support ◽  
High Shear ◽  
High Shear Stress
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