Biorheology - Volume 26, issue 1

Article Type: Editorial

DOI: 10.3233/BIR-1989-26110

Citation: Biorheology, vol. 26, no. 1, pp. I-III, 1989

Authors: Dutta, A. | Tarbell, J.M.

Article Type: Research Article

Abstract: Numerical simulations of flow in straight elastic (moving wall) tubes subjected to a sinusoidal pressure gradient were performed for conditions prevailing in large and medium sized arteries. The effects of varying the phase angle between the pressure gradient and the tube radius, the amplitude of wall motion, and the unsteadiness parameter (α ) on flow rate and wall shear stress were investigated. Mean and peak flow rates and shear stresses were found to be strongly affected by the phase angle between the pressure gradient and the tube radius with greater sensitivity at higher diameter variation and higher α . In …large artery simulations (α = 12), mean flow rate was found to be 60% higher and peak flow rate to be 73% higher than corresponding rigid tube values for certain phase angles, while a threefold increase in mean wall shear stress and sevenfold increase in peak wall shear stress were observed in a sensitive phase angle range. Significant reversal in the wall shear stress direction occurred in the sensitive phase angle range even when there was negligible flow rate reversal. All effects were greatly diminished in simulations of medium sized vessels (α = 4). Some experimental evidence to support the predictions of a strong effect of phase angle on wall shear stress in large vessels is presented. Finally, physiological implications of the present work are discussed from a basis of aortic input impedance data, and a physical explanation for the extreme sensitivity of the flow field to small amplitude wall motion at high α is given. Show more

Keywords: Wall shear stress, sinusoidal flow, elastic tube, phase angle, atherosclerosis, impedance

DOI: 10.3233/BIR-1989-26101

Citation: Biorheology, vol. 26, no. 1, pp. 1-22, 1989

Authors: Misra, J.C. | Kar, B.K.

Article Type: Research Article

Abstract: Taking into consideration the slip velocity at the wall of a blood vessel, a mathematical model is developed in the paper for the study of blood flow through a mammalian blood vessel in the presence of a stenosis. By employing the momentum integral technique, analytical expressions for the velocity profile, pressure gradient and skin-friction are derived. The condition for an adverse pressure gradient is also deduced. It is observed that the slip velocity bears the potential to influence the velocity distribution of blood to a remarkable extent and to reduce considerably the pressure-gradient as well as the skin-friction.

Keywords: Stenosis, Slip velocity, Skin-friction

DOI: 10.3233/BIR-1989-26102

Citation: Biorheology, vol. 26, no. 1, pp. 23-35, 1989

Authors: Easthope, Peter

Article Type: Research Article

Abstract: A three-dimensional dyadic form of the Walburn-Schneck constitutive equation for blood is presented. The dyadic equation is demonstrated to have the symmetries of material frame indifference and flow reversal and to be consistent with the scalar equation in Couette flow. The problem of flow in a tube of circular cross section is solved as an example.

Keywords: blood, constitutive, equation, viscosity

DOI: 10.3233/BIR-1989-26103

Citation: Biorheology, vol. 26, no. 1, pp. 37-44, 1989

Authors: Tajima, M. | Araiso, T. | Koyama, T. | Fujinaga, T. | Otomo, K. | Koike, T.

Article Type: Research Article

Abstract: The membrane viscosity of peripheral blood lymphocytes (PBLs) of equine, bovine and canine was measured by the use of time-resolved fluorescence depolarization technique with 1,6-diphenyl-1,3,5-hexatriene(DPH). The viscosity values were 0.55, 0.59 and 0.50 poise for equine, bovine and canine PBLs, respectively. These values were compared with steady-state anisotropies and order parameters measured from electron spin resonance (ESR) of 5-doxyl stearic acid. Both values were increased with increase of viscosity. The fluid property of the membranes stimulated with phytohemagglutinin-P (PHA) was measured with steady-state fluorescence anisotropy and ESR. Little change of membrane fluidity was recognized with both methods during the …stimulation with PHA. It appears that PHA activation process for these lymphocytes does not include large increase of the membrane fluidity which significantly accelerate the diffusion velocity of receptors in the plasma membrane. Show more

Keywords: lymphocyte, membrane fluidity, PHA stimulation, fluorescence depolarization, ESR

DOI: 10.3233/BIR-1989-26104

Citation: Biorheology, vol. 26, no. 1, pp. 45-54, 1989

Authors: Huyghe, Jacques M. | Oomens, Cees W. | van Campen, Dick H. | Heethaar, Robert M.

Article Type: Research Article

Abstract: A mixture theory has been used to formulate a theory of blood perfusion. By means of a formal averaging procedure the discrete network of microvessels is transformed into a continuum. During this procedure, the distinction between arterioles, capillaries and venules is preserved by means of an arteriovenous parameter. In this paper, two equations are derived for the case of low Reynolds number steady-state flow through a rigid vessel network: the extended Darcy equation and the continuity equation. A verification of the theory is presented, on the basis of a network analysis.

Keywords: porous media, mixture, regional blood flow, collateral flow, Darcy, averaging

DOI: 10.3233/BIR-1989-26105

Citation: Biorheology, vol. 26, no. 1, pp. 55-71, 1989

Authors: Huyghe, Jacques M. | Oomens, Cees W. | van Campen, Dick H.

Article Type: Research Article

Abstract: This research aims at formulating and verifying a finite element mixture formulation for blood perfusion. The equations derived in a companion paper [Huyghe, J.M., Oomens, C.W., Campen, D.H., van Heethaar, R.M., A mixture theory of low Reynolds steady state flow through a branching network of rigid vessels. Biorheology, submitted for publication, 1988.] are discretized according to the Galerkin method. A flow experiment in a rigid model of a vascular tree of about 500 vessels is performed in order to verify the finite element mixture formulation. Although the comparison of numerical results and experimental measurements is not conclusive as far as …the validity of the theory is concerned, the results do suggest that the finite element model has predictive power in the case of low Reynolds number steady state flow of a Newtonian fluid in a rigid vascular tree. Show more

Keywords: porous media, mixture, regional blood flow, collateral flow, finite element method, averaging

DOI: 10.3233/BIR-1989-26106

Citation: Biorheology, vol. 26, no. 1, pp. 73-84, 1989

Authors: Singh, M. | Ramesh, A.T.V.

Article Type: Short Communication

Keywords: hematocrit, tomography, axial migration and tubular pinch effects

DOI: 10.3233/BIR-1989-26107

Citation: Biorheology, vol. 26, no. 1, pp. 85-89, 1989

Article Type: Announcement

DOI: 10.3233/BIR-1989-26108

Citation: Biorheology, vol. 26, no. 1, pp. 91-94, 1989

Article Type: Other

DOI: 10.3233/BIR-1989-26109

Citation: Biorheology, vol. 26, no. 1, pp. 95-96, 1989