Biorheology - Volume 9, issue 1

Authors: Kline, K.A. | Allen, S.J. | Keshavarzi, M.

Article Type: Research Article

Abstract: Dissipative effects due to hydrodynamic interactions between red cells are studied by describing blood rheology using polar fluid theory. Appropriate ranges of values for the two fluid substructure parameters are discussed. The problem of oscillatory motion of the fluid in a thin walled elastic tube is solved. The phase velocity ratio and transmission per wavelength are determined, as are other details of the motion of the fluid. It is found that hydrodynamic interactions between red cells significantly reduce the transmission per wavelength. Further, the discrepancy in phase between calculated and observed flow in the femoral artery that results from Womersley …’s [Phil. Mag. 46 , 199, 1955] theory appears to vanish entirely when one uses the present analysis to account for dissipative effects of cell interactions. Show more

DOI: 10.3233/BIR-1972-9101

Citation: Biorheology, vol. 9, no. 1, pp. 1-22, 1972

Authors: Cowin, S.C.

Article Type: Research Article

Abstract: It is argued that the theory of polar fluids does not adequately model blood flow in the microcirculation. The principal argument against the use of the theory is that, on one hand, most experimental evidence shows that a significant feature of blood flow in tubes of this size (i.e. 30–300 μ m) is that local hematocrit varies with radial position in the tube, while on the other hand, polar fluid theory contains no field variable one can associate with, or use to determine, the variation of local hematocrit with radial position. A corroborative argument is that polar fluid theory does …not predict a reduction in apparent viscosity in flow through tubes as tube diameter decreases while such a phenomenon is well known for blood. Show more

DOI: 10.3233/BIR-1972-9102

Citation: Biorheology, vol. 9, no. 1, pp. 23-25, 1972

Authors: Lorin, Martin I. | Denning, Carolyn R. | Mandel, Irwin D.

Article Type: Research Article

Abstract: Investigations of biochemical abnormalities of exocrine secretions in cystic fibrosis have failed to explain the plugging of organ passages so characteristic of this disease. The present study examined one of the physical properties of these secretions, namely, viscosity. A rotational viscometer was used to compare the viscosities of sweat, submaxillary saliva and duodenal fluid from patients with cystic fibrosis, with the same secretions from non-cystic patients with gastrointestinal symptoms and from normal subjects. Qualitatively, the viscometric characteristics of each secretion were found to be the same for the two groups. Sweat, both cystic and normal, behaved as a Newtonian fluid, …with a constant viscosity at all rates of shear. Saliva, both cystic and normal, and duodenal fluid, cystic and noncystic, were all found to be pseudoplastic, with decreasing viscosity at increasing rates of shear. Quantitatively, a significant difference was present only for duodenal fluid, which was more viscous for the cystic fibrosis group. Show more

DOI: 10.3233/BIR-1972-9103

Citation: Biorheology, vol. 9, no. 1, pp. 27-32, 1972

Authors: Aroesty, J. | Gross, J.F.

Article Type: Research Article

Abstract: Recent experiments in vivo indicate that there are substantial regions of pulsatile flow throughout the microcirculation. Other experiments, performed with blood in vitro in various viscometric systems, have shown that the steady flow of blood can be represented by the parameters appropriate to a Casson fluid (yield stress, shear-dependent viscosity, power law of one half). The present study draws on these experimental observations, and on our recent mathematical analysis, to illustrate possible pulsatile effects upon the flow of blood in vessels of the scale of venules and arterioles. In our analysis, it was demonstrated that a quasi-steady …theory, valid for small values of α , the Womersley frequency parameter, was a good approximation under conditions of physiological relevance. The results of a mathematical analysis include a thin wall layer having a Newtonian viscosity significantly less than that in the Casson-fluid core. Such a layer can be crucial in determining the flow properties of the system. Illustrations of representative instantaneous velocity and flow rate distributions are presented, and the surprisingly large effects due to the lubricating qualities of a less viscous peripheral layer on the pulsatile flow of the Casson fluid in the core are exhibited. Show more

DOI: 10.3233/BIR-1972-9104

Citation: Biorheology, vol. 9, no. 1, pp. 33-43, 1972

Article Type: Abstract

DOI: 10.3233/BIR-1972-9105

Citation: Biorheology, vol. 9, no. 1, pp. 45-48, 1972