Biorheology - Volume 9, issue 4

Authors: Gauthier, F.J. | Goldsmith, H.L. | Mason, S.G.

Article Type: Research Article

Abstract: The translational velocities, paths and deformation of liquid drops in mono disperse emulsions flowing through rigid tubes of 1 cm radius at particle Reynolds numbers < 10−5 have been measured. The mean drop radii varied from 0.042 to 0.055 cm, the mean linear flow rates from 0.004 to 0.1 cm sec−1 and the volume concentrations from 14 to 37 per cent. As previously found in suspensions of rigid spheres, the velocity distributions at a given volume flow rate were blunted at concentrations above 25 per cent with partial plug flow developing in the core of the tube. …However, the extent of plug flow at a given concentration and particle size was smaller in the emulsions and decreased with increasing flow rate, and at a given flow rate, with increasing suspending phase viscosity. When the emulsions were broken up by stirring the mean drop radius decreased to 5 × 10−3 cm and the velocity profiles were parabolic at all flow rates. The deformed drops migrated away from the tube wall at rates which fluctuated as particles collided with each other, and decreased to zero in the core of the tube. Here, in the particle crowded suspension, the drop paths were also subject to sideways fluctuations and the particles were distorted as they squeezed past each other. In contrast to rigid sphere suspensions, the paths were not reversible when the flow was reversed. Comparison with data obtained in human ghost cell and red cell suspensions showed that at given values of the shear deformation parameter, the degree of blunting of the velocity profile was similar in the different systems. Show more

DOI: 10.3233/BIR-1972-9401

Citation: Biorheology, vol. 9, no. 4, pp. 205-224, 1972

Authors: Gross, Joseph F. | Aroesty, Jerome

Article Type: Review Article

Abstract: The elements of the mathematical analysis of capillary flow are presented and various models of different degrees of complexity and physiological relevance are critically discussed. The occlusion experiment and its importance for the determination of mass transport properties in the microcirculation is described in detail. Unresolved fluid-mechanical problems are examined and important areas for future research are suggested.

DOI: 10.3233/BIR-1972-9402

Citation: Biorheology, vol. 9, no. 4, pp. 225-264, 1972

Authors: Barnett, B. | Meilman, E. | Han, C.D.

Article Type: Research Article

Abstract: The viscoelastic properties of blood serum were measured by means of a capillary viscometer described in earlier papers by the authors. The capillary viscometer constructed earlier was further modified by the use of Teflon as part of the capillary section. Changes in viscosity and recoverable shear strain were determined as a function of time on samples from patients who underwent open heart surgery. The measured values showed marked changes in both viscosity and elastic shear modulus immediately following, and for some time after, surgery.

DOI: 10.3233/BIR-1972-9403

Citation: Biorheology, vol. 9, no. 4, pp. 265-271, 1972

Authors: Procita, Leonard | Hunt, William

Article Type: Research Article

Abstract: A viscometric and electrophoretic study of the deformation and flow properties of R-actomyosin induced by adenosinetriphosphate and other adenine nucleotides. The deformation and flow changes induced in R-actomyosin by adenine nucleotides have been studied by electrophoresis and viscometric methods under identical experimental conditions of ionic strength, pH, temperature, protein and nucleotide concentration. The data show that a concentration of nucleotide which produces a maximal decrement of the reduced viscosity of an R-actomyosin solution does not effect a change in the electrophoretic pattern from a single component to a multicomponent system. Greater concentrations of nucleotide, however, while effecting the same viscosity …change as the smaller concentrations, do produce electrophoresis patterns with 3, 4 or more components. The intrinsic viscosity value of R-actomyosin in the presence of ATP is significantly reduced from its value in the absence of ATP. This implies a reduction in the size and/or shape of this macromolecular entity. The results obtained, not only with ATP, but also with ADP, AMP and ITP, cannot be interpreted in concert with the classical concept of a dissociation of actomyosin into simply F-actin and myosin A. Show more

DOI: 10.3233/BIR-1972-9404

Citation: Biorheology, vol. 9, no. 4, pp. 273-285, 1972

Authors: Kline, Kenneth A.

Article Type: Research Article

Abstract: An improved theory for the deformation of a liquid drop subjected to uniform shear is applied to the problem of a liquid drop suspended in a nonuniform shear field. A solution is given for slow flow between fixed parallel plates of a dilute suspension of liquid drops, and dimensionless velocity profiles and average velocity are calculated. The liquid drop model is applied to blood rheology using published estimates for red cell viscosity and membrane tension. The velocity profiles are found to be blunter than parabolic, with the degree of blunt- ing increasing with cell concentration. The profiles are not as …blunt as those observed generally, indicating effects of hydrodynamic interactions between neighboring red cells and between cells and the walls need be taken into account to model blood rheology. It is deduced that measurements of the first normal stress difference will provide the best means for studying erythrocyte rheology within the context of the liquid drop model. Show more

DOI: 10.3233/BIR-1972-9405

Citation: Biorheology, vol. 9, no. 4, pp. 287-299, 1972