Flow instability due to coupling of shear-gradients with concentration: non-uniform flow of (hard-sphere) glasses

Soft Matter ◽  
2014 ◽  
Vol 10 (47) ◽  
pp. 9470-9485 ◽  
Author(s):  
Howon Jin ◽  
Kyongok Kang ◽  
Kyung Hyun Ahn ◽  
Jan K. G. Dhont
Keyword(s):  
Shear Rate ◽  
Hard Sphere ◽  
Flow Instability ◽  
Microscopic Theory ◽  
Shear Rates ◽  
Spatial Gradients ◽  
Flow Profiles ◽  
Mass Fluxes ◽  
Glassy Systems ◽  
Low Shear

A microscopic theory explains the origin of mass fluxes induced by spatial gradients in the shear rate, and leads to an expression for the corresponding transport coefficient. The resulting instability gives rise to banded flow profiles in glassy systems for low shear rates.

Whole blood viscosity in the evaluation of thrombogenic milieu in mitral stenosis

2021 ◽  
Vol 15 (3) ◽  
pp. 181-190
Author(s):  
Elif H Ozcan Cetin ◽  
Mehmet S Cetin ◽  
Mustafa B Ozbay ◽  
Hasan C Könte ◽  
Nezaket M Yaman ◽  
...  
Keyword(s):  
Shear Rate ◽  
Blood Viscosity ◽  
Whole Blood ◽  
Mitral Stenosis ◽  
High Shear Rate ◽  
High Shear ◽  
Whole Blood Viscosity ◽  
Spontaneous Echo Contrast ◽  
Shear Rates ◽  
Low Shear

Aim: We aimed to assess the association of whole blood with thromboembolic milieu in significant mitral stenosis patients. Methodology & results: We included 122 patients and classified patients into two groups as having thrombogenic milieu, thrombogenic milieu (+), otherwise patients without thrombogenic milieu, thrombogenic milieu (-). Whole blood viscosity (WBV) in both shear rates were higher in thrombogenic milieu (+) group comparing with thrombogenic milieu (-). WBV at high shear rate and WBV at low shear rate parameters were moderately correlated with grade of spontaneous echo contrast. Adjusted with other parameters, WBV parameters at both shear rates were associated with presence of thrombogenic milieu. Discussion & conclusion: We found that extrapolated WBV at both shear rates was significantly associated with the thrombogenic milieu in mitral stenosis. This easily available parameter may provide additional perspective about thrombogenic diathesis.

Rheology of Fluoride Gels

1976 ◽  
Vol 55 (3) ◽  
pp. 353-356 ◽  
Author(s):  
M. Braden ◽  
Ratna Perera
Keyword(s):  
Infrared Spectroscopy ◽  
Shear Rate ◽  
Elastic Behavior ◽  
Shear Stresses ◽  
High Shear ◽  
Shear Rates ◽  
Extreme Stress ◽  
Thickening Agents ◽  
Shear Rate Dependence ◽  
Low Shear

Six commercial fluoride gels have been studied, using a cone and plate viscometer. Also, the thickening agents have been analyzed using infrared spectroscopy. All gels showed stress thinning, which is the decrease of viscosity with shear rate. Such shear rate dependence is clinically convenient in that the gel will flow readily at the high shear stresses present when the gel is applied but will not flow readily under its own weight when on the tooth. Five materials containing hydroxyalkyl celluloses showed similar degrees of shear thinning. One material with a non-cellulosic thickener showed much more extreme stress thinning together with elastic behavior at low shear rates; such behavior may be clinically advantageous. All of the gels showed only slight temperature dependence of rheological properties.

The Simulation of Aggregated Colloids Under Flow

1992 ◽  
Vol 289 ◽  
Author(s):  
John R. Melrose
Keyword(s):  
Shear Rate ◽  
Large Scale ◽  
Shear Thinning ◽  
High Shear ◽  
Shear Rates ◽  
Rouse Model ◽  
High Shear Rates ◽  
Structural Breakdown ◽  
Large Scale Simulations ◽  
Low Shear

AbstractAn overview is given of theories of aggregates under flow. These generally assume some sort of structural breakdown as the shear rate is increased. Models vary with both the rigidity of the bonding and the level of treatment of hydrodynamics. Results are presented for simulations of a Rouse model of non-rigid, (i.e. central force) weakly bonded aggregates. In large scale simulations different structures are observed at low and high shear rates. The change from one structure to another is associated with a change in the rate of shear thinning. The model captures low shear rate features of real systems absent in previous models: this feature is ascribed to agglomerate deformations. Quantitatively, the model is two orders of magnitude out from experiment but some scaling is possible.

Direct Measurement of Slip Velocities Using Three-Dimensional Total Internal Reflection Velocimetry

2005 ◽  
Author(s):  
Peter Huang ◽  
Jeffrey Guasto ◽  
Kenneth Breuer
Keyword(s):  
Shear Rate ◽  
Total Internal Reflection ◽  
Three Dimensional ◽  
Surface Hydrophobicity ◽  
Internal Reflection ◽  
Boundary Slip ◽  
Shear Rates ◽  
Rate Dependent ◽  
Close Proximity ◽  
Low Shear

The possible existence of slip of liquids in close proximity to a smooth surface is studied experimentally via the dynamics of small particles suspended in a shear flow. Sub-micron fluorescent particles suspended in water are imaged and analyzed using Total Internal Reflection Velocimetry (TIRV). For water flowing over a hydrophilic surface, the measurements are in agreement with previous experiments and indicate that slip, if present, is minimal at low shear rates, but increases slightly as the shear rate increases. Furthermore, surface hydrophobicity can be attributed for additional shear-rate dependent boundary slip. Issues associated with the experimental technique and the interpretation of results are also discussed.

Transfusion Therapy Decreases Oxygen Transport to Low-Flow Vascular Beds in Sickle Cell Disease.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1518-1518
Author(s):  
Tamas Alexy ◽  
Thomas D. Coates ◽  
John C Wood ◽  
Herbert J. Meiselman ◽  
Rosalinda B Wenby ◽  
...  
Keyword(s):  
Shear Rate ◽  
Oxygen Transport ◽  
Blood Viscosity ◽  
Low Flow ◽  
High Shear ◽  
Cell Disease ◽  
Blood Samples ◽  
Shear Rates ◽  
Low Shear ◽  
High Risk Children

Abstract Abstract 1518 Poster Board I-541 Introduction Chronic blood transfusions are commonly used as therapy for sickle cell disease (SCD, HbSS) in order to improve oxygen delivery and minimize complications such as stroke in high-risk children. Vaso-occlusive crises can occur in regions of high shear flow (e.g., major cerebral artery occlusions) or regions of low shear flow (e.g., marrow infarct) leading to acute ischemia and, if severe, to necrosis of affected tissues. Transfusion with normal (AA) RBC causes an increase of hematocrit (H) that is complicated by two opposing factors: increased hematocrit (H) causes a linear increase of oxygen carrying capacity and also an exponential increase of blood viscosity (η). As a consequence, the calculated oxygen transport effectiveness, defined as the ratio of H to η (H/η), is a biphasic function of hematocrit: H/η initially increases with H, reaches a maximum at an optimal H value, and then declines with further increases of H. At equal H and shear rate, sickle (SS) blood has significantly higher viscosity than AA and hence part of the strategy for transfusing SCD patients is to reduce η so as to improve H/η. Viscosity studies at high shear rates indicate that an optimum H can be demonstrated for AA-SS RBC mixtures prepared by adding AA RBC to SS blood to simulate transfusion. In marked contrast, low shear rate results for AA-SS mixtures indicate that there is no optimum hematocrit and H/η always decreases with increasing H (Transfusion 46:912-918, 2006). In order to extend these previous in vitro observations to SCD patients, we have measured blood viscosity and hematocrit using whole blood samples acquired prior to and following routine therapeutic transfusion; H/η was calculated over a wide, physiologically relevant shear rate range. Methods All subjects (n= 8, mean age =18.7 years) had homozygous HbSS disease, were crisis-free for > 4 weeks, and were enrolled in a chronic transfusion protocol designed to yield < 30% HbS and a post-transfusion H of 30-35%. Blood samples were obtained pre- and within 120 hours post-transfusion. A computer-controller tube viscometer was used to determine blood viscosity (37 °C, 40 mm Hg oxygen tension) over a shear rate range of 1 – 1,000 1/s. Results 1) As anticipated, blood viscosity and the degree of non-Newtonian flow behavior increased with H (24.7% pre-transfusion, 34.6% post-transfusion); 2) the change of H/η from pre- to post- transfusion was markedly affected by shear rate (Figure). As indicated, there is a large adverse effect at low shear (i.e., H/η reduced by 20-25% following transfusion), a neutral effect at about 50-100 1/s, and an improved H/η at high shear (Figure). That is, transfusion with AA RBC to obtain a lower percent SS RBC and a higher H actually impairs oxygen transport effectiveness at low shear and is only beneficial at high shear. Conclusions Clinical experience suggests that transfusion regimens aimed a keeping HbS at 30-50% are effective in preventing recurrent strokes in high-risk children. However, our new in vivo transfusion data suggest that at low shear rates, %HbS must be reduced further for H/η to surpass pre-transfusion levels. We interpret these findings as being consistent with our previous data for AA-SS RBC mixtures. They are also consistent with clinical results indicating lack of efficacy for transfusion in low flow areas (e.g., bone marrow during acute crisis) but highly beneficial effects in high flow regions (e.g., cerebral arteries). Our results thus suggest that benefits of transfusion may vary depending on local flow rates (i.e., shear rates) and organ-specific hemodynamics. Disclosures No relevant conflicts of interest to declare.

Rheology and Component Interactions in Tape Casting Slurries

1985 ◽  
Vol 60 ◽  
Author(s):  
John R Morris ◽  
W Roger Cannon
Keyword(s):  
Shear Rate ◽  
Rheological Behavior ◽  
Tape Casting ◽  
Relative Viscosity ◽  
Shear Rates ◽  
Viscosity Measurements ◽  
The Stability ◽  
Low Shear

AbstractRheology and the component interactions which affect rheology were studied for a tape casting composition similar to commercial systems. Viscosity measurements at different shear rates were compared to measured tape properties to determine if high or low shear rate rheological behavior controls tape characteristics. Relative viscosity was measured to assess the contribution of each component to the stability of the dispersion.

scholarly journals Rheological properties of traditional balsamic vinegar: New insights and markers for objective and perceived quality

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Pasquale M. Falcone ◽  
Elisa Sabatinelli ◽  
Federico Lemmetti ◽  
Paolo Giudici
Keyword(s):  
Shear Rate ◽  
Rheological Properties ◽  
Dynamic Viscosity ◽  
Flow Instability ◽  
Relaxation Times ◽  
Sensory Properties ◽  
Flow Behaviour ◽  
Shear Rates ◽  
Wide Range ◽  
Balsamic Vinegar

The molecular structure of Traditional Balsamic Vinegar (TBV) undergoes shear-induced and time-dependent jamming transitions due to the high solute concentration and self-assembling phenomena of high molecular size melanoidins with very-long relaxation times (12 years at least or more than 25). The purpose of this work was to perform a descriptive and quantitativeevaluation of relationships between rheological properties, vinegar composition, and perceptual assessment of sensory properties according to the official sensory procedure. With this aim, vinegars having quality traits matching legal requirements for the PDO designation were analyzed for their reducing sugars (glucose and fructose), volatile acidity, fixed acidity, pH, Brix degree, and density as well as for their flow behaviour and dynamic viscosity over a wide range of shear rates. Results showed that flow behaviour of TBV was affected by jamming properties over wide-scale ranges of shear rate producing flow instability below a shear rate of 60s-1. Homogeneous, continuous flow was found at medium-high shear rates with thickening and/or thinning traits. A common onset for the structure scaling was mathematically estimated to occur close to when the density was 1.32 gmL-1. Comparative analysis of rheological, compositional and sensory properties suggested that the colloidal jamming of the vinegar melanoidins dominated the total olfactive and gustative stimuli, and determined the classification of the vinegars that had a higher dynamic viscosity but more homogeneous flow as being of the highest commercial quality category. A robust statistical model was proposed encoding for the top-down decision-making process for quality assignment according to the official sensory procedure, using composition and flow properties as predictor variables. 

Variable Shear Rate Viscosity of SBR-Filler-Plasticizer Systems

1974 ◽  
Vol 47 (4) ◽  
pp. 825-836 ◽  
Author(s):  
G. C. Derringer
Keyword(s):  
Shear Rate ◽  
Experimental Design ◽  
Individual Contribution ◽  
Model Application ◽  
Shear Rates ◽  
Variable Shear ◽  
Wide Range ◽  
Mooney Viscosity ◽  
The Individual ◽  
Low Shear

Abstract Variable shear rate viscosity studies of compositions with variable filler and plasticizer levels have led to the development of a unifying viscosity model. Application of the model indicated that the fillers studied are less effective as stiffeners at shear rates typical of factory processing operations than at the low shear rates characteristic of the Mooney viscosity test. Thus, for proper comparative evaluations of pigment effect on processing, Mooney measurements are inadequate. The effect of shear rate on plasticizer efficiency will require more work to make definitive statements. Plasticizer evaluations appear to be a fruitful avenue for further exploration. The model developed has proved useful in understanding the individual contribution to the viscosity of the compound by the raw elastomer, the filler, and the plasticizer over a wide range of shear rates. The availability of this model will also result in an economy of experimentation as each shear rate of interest need not be studied separately. Having a valid model makes it possible to optimize the experimental design with regard to cost and information.

USING STEADY SHEAR RATE SWEEP PROTOCOL TO DETERMINE ZERO SHEAR VISCOSITY OF UNAGED AND AGED UNMODIFIED BITUMINOUS BINDERS

2021 ◽  
Author(s):  
Syed Mubashirhussain ◽  
Venkaiah Chowdary
Keyword(s):  
Shear Rate ◽  
Shear Viscosity ◽  
Steady Shear ◽  
Zero Shear Viscosity ◽  
Shear Rates ◽  
Bituminous Mixtures ◽  
Bituminous Binders ◽  
Bituminous Pavements ◽  
Low Shear

Rutting is one of the most significant distresses occurring in bituminous pavements at higher pavement temperatures. Researchers have been focusing on developing bitumen binder parameters that can be used to predict the rutting resistance of bituminous mixtures and Zero Shear Viscosity (ZSV) has proven its efficacy as a binder rutting parameter. A stepwise steady shear rate sweep test with two cycles of forward and backward sweeps was conducted at very low shear rates to determine the ZSV of unaged, short-term aged, and long-term aged unmodified bitumen binders. A convergence of the steady-state viscosities was observed at different shear rates in the first forward sweep. The response of the binders was independent of shear rate, time and the effect of shear history was negligible. As the shear rates correspond to the ZSV regime, ZSV was determined from the first forward sweep. The ZSV correlated well with the three existing rutting parameters.

Molecular determinants of shear rate-dependent leukocyte adhesion in postcapillary venules

1993 ◽  
Vol 264 (5) ◽  
pp. H1504-H1508 ◽  
Author(s):  
K. Bienvenu ◽  
D. N. Granger
Keyword(s):  
Shear Rate ◽  
Mesenteric Arteries ◽  
Intercellular Adhesion Molecule ◽  
Leukocyte Rolling ◽  
Shear Rates ◽  
Rate Dependent ◽  
Molecular Determinants ◽  
Rolling Leukocytes ◽  
Adherent Leukocytes ◽  
Low Shear

Recent studies have demonstrated that reductions in shear rate are associated with the recruitment of rolling and adherent leukocytes in postcapillary venules. The objective of this study was to define the molecular determinants of the leukocyte-endothelial cell adhesive interactions elicited by low venular shear rates. Three different monoclonal antibodies (MAb) were used to assess the relative contributions of CD18 (MAb R15.7), intercellular adhesion molecule 1 (ICAM-1; MAb RR1/1), and P-selectin (MAb PB1.3) to shear rate-dependent leukocyte rolling and adherence. Erythrocyte velocity, vessel diameter, leukocyte adherence, and leukocyte rolling velocity were monitored in cat mesenteric venules (25-40 microns diam). Venular shear rate was varied in a stepwise fashion by graded occlusion of an arterial circuit between the femoral and superior mesenteric arteries. Shear rates were maintained at each level for a period of 2 min. The MAbs directed against either CD18 or ICAM-1, but not P-selectin, significantly attenuated the recruitment of adherent leukocytes normally observed at low shear rates. However, the MAb against P-selectin, but not CD18 or ICAM-1, was effective in reducing the recruitment of rolling leukocytes elicited by low shear rates. These observations indicate that shear rate-dependent recruitment of adherent leukocytes involves an interaction between CD11/CD18 on leukocytes and ICAM-1 on vascular endothelium, while P-selectin on endothelial cells mediates, at least part of, the recruitment of rolling leukocytes.

Sign in / Sign up

Export Citation Format

Share Document