Biorheology - Volume 20, issue 6

Authors: Copley, Alfred L. | Silberberg, Alex

Article Type: Editorial

DOI: 10.3233/BIR-1983-20601

Citation: Biorheology, vol. 20, no. 6, pp. 731-731, 1983

Authors: Chaturani, P. | Biswas, D.

Article Type: Research Article

Abstract: In this paper, Couette flow of blood is modelled as a three-layered flow. The model basically consists of a core (red-cell suspension) and plasma (a Newtonian fluid) in the top (near the moving plate) and bottom (near the stationary plate) layers. Flow is assumed to be steady and laminar and fluids are incompressible. A spin boundary condition at the interfaces is used by introducing two parameters. Analytic expressions for velocity, total angular velocity and effective viscosity have been obtained and their variations with spin parameters S and s, layer thickness, coupling number N and characteristic length ratio L are computed …and shown graphically. One of the important observations of the analysis is the permissible values of the coupling number N is between 0 and 1 / 2 (in the existing literature, the range of N is 0 to 1). The present model include s Couette f low of one and three-layered Newtonian fluids and one-layered polar fluid models as its special cases. Applications of the proposed model to blood flow have been briefly discussed. Show more

Keywords: Viscosity, velocity profiles, blood flow

DOI: 10.3233/BIR-1983-20602

Citation: Biorheology, vol. 20, no. 6, pp. 733-744, 1983

Authors: Moravec, S. | Liepsch, D.

Article Type: Research Article

Abstract: Together with biochemical factors, fluid mechanical factors play a role in atherogenesis and the deposition of blood platelets at bends and bifurcations in human arteries. Hence, flow patterns were investigated in a simplified 3-dimensional model of a human renal artery bifurcation using Newtonian (aqueous glycerol) and non-Newtonian (aqueous solution of polyacrylamide) fluids. Studies were carried out in steady as well as pulsatile flow at inflow Reynolds numbers of 498 and 951 with flow rate ratios main tube V ˙ 1: right branch V ˙ 4: left branch V ˙ …3 of 1: 0.25: 0.25 and 1: 0.18: 0.18 respectively. The velocity distribution proximal and distal to the bifurcations was measured using a laser-Doppler anemometer. In steady flow, zones of flow separation and reverse flow were observed distal to the bifurcations. In pulsatile flow using non-Newtonian fluids, there was a significant enlargement of these zones. Differences between the Newtonian and non-Newtonian fluids occurred especially distal to the bifurcations. Shear stresses along all measuring positions were computed from the velocity gradients. Show more

Keywords: Flow, Artery model, Fluid: Newtonian, non-Newtonian

DOI: 10.3233/BIR-1983-20603

Citation: Biorheology, vol. 20, no. 6, pp. 745-759, 1983

Authors: Srivastava, L.M. | Srivastava, V.P.

Article Type: Research Article

Abstract: A particle fluid suspension model is applied to the problem of pulsatile blood flow through a rigid circular tube with entrance effects. Flow is generated by an arbitrary (time and axial flow variable dependent) as well as a particular pressure gradient of physical importance. Fluid and particle phase velocities are explicitly determined for both, with and without entrance effects. Further, steady pulsatile velocities for both cases are deduced by taking time t → ∞ . Several other limiting cases of physical and biological importance have been obtained and discussed in detail.

Keywords: Blood flow, Entrance effects

DOI: 10.3233/BIR-1983-20604

Citation: Biorheology, vol. 20, no. 6, pp. 761-777, 1983

Authors: Koutsouris, D. | Hanss, M. | Skalak, R.

Article Type: Research Article

Abstract: Filtration experiments through 5 or 3μ Nuclepore membranes are often performed in order to assess the so-called erythrocyte deformability. The relation between this parameter and the RBC filterability is not straightforward. A simple theoretical treatment relating filtration index (as determined by the initial flow rate method) to the average RBC flow resistance through an average pore is presented. In order to deduce the average RBC transit time through the membrane from the initial flow rate data, the suspension hematocrit change after filtration has been determined. The calculated average transit time is comparable to experimental values, as determined by Kiesewetter …et al. with the single pore technique. Show more

Keywords: Rigidity index, Erythrocyte deformability, Erythrocyte filtrability, Membrane transit times

DOI: 10.3233/BIR-1983-20605

Citation: Biorheology, vol. 20, no. 6, pp. 779-787, 1983

Authors: Kafka, V.

Article Type: Research Article

Abstract: Hydraulic strengthening of bones - i.e. the strengthening effect of the viscous fluid in bones - is discussed and the contradicting results: of some researches concerning the existence of hydraulic strengthening are estimated. It is concluded that hydraulic strengthening exists and has an important positive effect upon the mechanical behaviour of bone, especially of cancellous bone. General features of an adequate mathematical model for the mechanical behaviour of cancellous bone are specified.

Keywords: Biomechanics, bone, spongiosa, viscoelasticity, structure, strengthening

DOI: 10.3233/BIR-1983-20606

Citation: Biorheology, vol. 20, no. 6, pp. 789-793, 1983

Authors: Kafka, V. | Jírová, J.

Article Type: Research Article

Abstract: The presented paper is based on the conclusions of the preceding paper (1). On the basis of a general theoretical approach to the mechanics of heterogeneous materials published earlier /(2) , (3) , (4)/ macroscopic constitutive equation of trabecular bone is deduced from the description of its microstructure. For the behaviour in physiological limits trabeculae are described as elastic and the remaining material constituent as a Maxwell body. The resulting macroscopic constitutive equation comprehends tensorial internal variables and the parameters appearing in it are the constants of the material constituents constitutive equations, the respective volume fractions and special structural parameters …descriptive of the geometry of composition. The system of the trabeculae as well as the system of the remaining constituent of the composite are considered to be interconnected - continuous. Explicite formulae are given for the case of transverse isotropy, but the extension to more general cases of anisotropy is well possible. The procedure of identification of the model parameters is shown and a numerical example calculated. Show more

Keywords: Biomechanics, bone, spongiosa, viscoelasticity, structure, mathematical model

DOI: 10.3233/BIR-1983-20607

Citation: Biorheology, vol. 20, no. 6, pp. 795-805, 1983

Authors: Chaturani, P. | Biswas, D. | Mahajan, S.P.

Article Type: Letter

Keywords: Two-fluid model, Slip, Blood flow, Small diameter tubes, Rotational velocity

DOI: 10.3233/BIR-1983-20608

Citation: Biorheology, vol. 20, no. 6, pp. 807-809, 1983

Article Type: Abstract

DOI: 10.3233/BIR-1983-20610

Citation: Biorheology, vol. 20, no. 6, pp. 811-825, 1983

Authors: Copley, A.L.

Article Type: Abstract

DOI: 10.3233/BIR-1983-20609

Citation: Biorheology, vol. 20, no. 6, pp. 811-811, 1983

Article Type: Abstract

DOI: 10.3233/BIR-1983-20611

Citation: Biorheology, vol. 20, no. 6, pp. 827-838, 1983

Article Type: Other

DOI: 10.3233/BIR-1983-20612

Citation: Biorheology, vol. 20, no. 6, pp. 839-854, 1983