Effects of Matrix Viscoelasticity on Rheology of Dilute and Semi-Dilute Suspensions of Non Brownian Rigid Spheres

2008 ◽  
Author(s):  
Nino Grizzuti ◽  
Rossana Pasquino ◽  
Albert Co ◽  
Gary L. Leal ◽  
Ralph H. Colby ◽  
...  
Keyword(s):  
Rigid Spheres ◽  
Dilute Suspensions

The flow of suspensions through tubes. III. Collisions of small uniform spheres

1964 ◽  
Vol 282 (1391) ◽  
pp. 569-591 ◽  
Keyword(s):  
Steady State ◽  
Couette Flow ◽  
Poiseuille Flow ◽  
Collision Frequency ◽  
Reynolds Numbers ◽  
Tube Axis ◽  
Rigid Spheres ◽  
Liquid Drops ◽  
Net Migration ◽  
Dilute Suspensions

Two-body interactions of small rigid and deformable spheres in dilute suspensions undergoing Poiseuille flow at Reynolds numbers less than 10 –3 were studied and found to be similar to those previously observed in Couette flow. Two-body collisions between rigid spheres were symmetrical and reversible, the paths of approach and recession being curvilinear and mirror images of one another, except near the wall. The measured collision frequency agreed well with a theory based on rectilinear approach and recession, whereas the measured steady-state number of doublets was twice that predicted by the theory. The discrepancy was in part due to the existence of non-sepa­rating doublets, the orbits of which were also studied. In contrast, collisions between liquid drops were unsymmetrical, thus providing a mechanism for net migration of drops towards the tube axis in addition to the axial migration previously observed with single deformed drops.

Interrelationships of Particle Structure and Flow in Concentrated Suspensions

MRS Bulletin ◽  
1991 ◽  
Vol 16 (8) ◽  
pp. 32-37 ◽  
Author(s):  
Richard L. Hoffman
Keyword(s):  
Particle Concentration ◽  
Flow Behavior ◽  
Particle Interactions ◽  
Particle Structure ◽  
Concentrated Suspensions ◽  
Rigid Spheres ◽  
Classical Work ◽  
Dilute Suspensions ◽  
Polymer Dispersions ◽  
Multiple Particle

Numerous commercial products either exist as concentrated suspensions of small particles or involve the processing of concentrated suspensions during some stage of their manufacture. Examples include foods, adhesives and glues, ceramic dispersions, paints, and polymer dispersions such as polyvinyl chloride plastisols. As a result, it is important for engineers to understand the flow behavior of these systems and how the flow behavior affects the way these materials can be processed.For mahy years, progress in understanding the flow behavior of concentrated suspensions was slow compared to progress on dilute systems, partly because of how the study of suspensions evolved. Building on Einstein's classical work for dilute suspensions of rigid spheres, many authors attempted to modify his equations to predict the flow behavior of more concentrated suspensions, but the extension of Einstein's work met with limited success, because nonhydrodynamic interactions cari be just as important as the hydrodynamic interactions considered by Einstein, and multiple particle interactions quickly complicate the problem as the particle concentration increases.

Effects of Prostaglandins, Derivatives of Cyclic 3':5'-AMP, Theophylline, Cholinergic Agents and Colchicine on Clot Retraction in Dilute Platelet-Rich Plasma and Gel-Separated Platelet Test Systems

1977 ◽  
Vol 38 (02) ◽  
pp. 0420-0428 ◽  
Author(s):  
J. L Moake ◽  
P. L Cimo ◽  
K Widmer ◽  
D. M Peterson ◽  
J. R Gum
Keyword(s):  
Platelet Rich Plasma ◽  
Inhibitory Effect ◽  
Fibrin Clot ◽  
Serotonin Release ◽  
Dibutyryl Camp ◽  
Clot Retraction ◽  
Dilute Suspensions ◽  
Cholinergic Agents ◽  
Camp Levels ◽  
Derivatives Of

SummaryIn dilute suspensions of platelet-rich plasma (PRP) or gel-separated platelets (GSP), dibutyryl-cAMP (DBcAMP) and monobutyryl-cAMP inhibited platelet-mediated fibrin clot retraction in concentrations of 2–3 × 10–6M, with complete inhibition at 1–3 × 10–4M. Prostaglandin E1 (PGE1), which inhibited fibrin clot retraction in concentrations greater than 1.5–3 × 10–8M, was a more effective inhibitor than either PGE2 or PGF2α. In the presence of theophylline (10–4M), concentrations of DBcAMP, PGE1 PGE2 and PGF2α necessary to inhibit fibrin clot retraction were reduced 50-fold for DBcAMP and 2.5 to 20-fold for the prostaglandins. In dilute PRP or GSP, inhibition of fibrin clot retraction does not result from inhibition of thrombin-induced platelet aggregation. Thus, compounds which increase platelet cAMP levels result in the inhibition of platelet-mediated fibrin clot retraction, and this inhibitory effect may be mediated, at least in part, through suppression of platelet contractility. Cyclic GMP, dibutyryl-cGMP and carbamylcholine-Cl (which stimulates guanylate cyclase) did not influence fibrin clot retraction, and did not prevent inhibition of fibrin clot retraction by DBcAMP and PGE?. Colchicine, in concentrations known to disrupt platelet microtubules (2.5 × 10–6M to 2.5 x 10–3M), had little inhibitory effect on either fibrin clot retraction or platelet (3H)-serotonin release.

A Mechanism for Non‐Newtonian Flow in Suspensions of Rigid Spheres

1959 ◽  
Vol 3 (1) ◽  
pp. 137-152 ◽  
Author(s):  
Irvin M. Krieger ◽  
Thomas J. Dougherty
Keyword(s):  
Newtonian Flow ◽  
Rigid Spheres

An improved formula for terminal velocity of rigid spheres

1997 ◽  
Vol 50 (1-2) ◽  
pp. 53-61 ◽  
Author(s):  
A.V. Nguyen ◽  
H. Stechemesser ◽  
G. Zobel ◽  
H.J. Schulze
Keyword(s):  
Terminal Velocity ◽  
Rigid Spheres

Sound waves in a periodic medium containing rigid spheres

1987 ◽  
Vol 82 (4) ◽  
pp. 1436-1441 ◽  
Author(s):  
Dov Bai ◽  
Joseph B. Keller
Keyword(s):  
Periodic Medium ◽  
Sound Waves ◽  
Rigid Spheres

Kinetics of flowing dispersions. X. Oscillations in optical properties of streaming suspensions of spheroids

1977 ◽  
Vol 55 (24) ◽  
pp. 4243-4256 ◽  
Author(s):  
A. Okagawa ◽  
S. G. Mason
Keyword(s):  
Light Scattering ◽  
Shear Flow ◽  
General Pattern ◽  
Relaxation Times ◽  
Simple Shear Flow ◽  
Scattering Coefficients ◽  
Human Red Blood Cells ◽  
Dielectric Particles ◽  
Dilute Suspensions ◽  
Orientation Distributions

Transients in angular light scattering and turbidity of dilute suspensions of nearly monodisperse spheroidal particles undergoing simple shear flow have been investigated by combining Rayleigh–Debye light scattering theory for single dielectric particles with fluid mechanical theory for the orientation distributions of particle assemblies in shear flow. Applying shear to an initially isotropic suspension causes the orientation distributions and thus the angular scattering coefficients to oscillate. Various geometrical arrangements are considered with a view to selecting those that will maximize such rheo-optical effects.By calculating the optical scattering cross section of a single particle, the turbidity of a suspension is obtained; like the scattering coefficient, it undergoes oscillations that are damped by (1) the inevitable spread in particle shape and volume in real systems, (2) shear-induced particle interactions, and (3) rotary Brownian motion. The rates of damping, expressed as relaxation times, are considered for the three mechanisms acting alone or in concert.Preliminary measurements of the turbidity of dilute suspensions of hardened human red blood cells confirm this general pattern of behavior. Apart from their intrinsic interest, such rheo-optical effects can be used to determine a number of useful properties of dispersions.

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