Biorheology - Volume 27, issue 5

Authors: Chaturani, P. | Palanisamy, V.

Article Type: Research Article

Abstract: A mathematical model has been proposed to study the pulsatile flow of a power-law fluid through rigid circular tubes under the influence of a periodic body acceleration. Numerical solutions have been obtained by using finite difference method. The accuracy of the numerical procedure has been checked by comparing the obtained numerical results with other numerical and analytical solutions. It is found that the agreement between them is quite good. Interaction of non-Newtonian nature of fluid with the body acceleration has been investigated by using the physiological data for two particular cases (coronary and femoral arteries). The axial velocity, fluid acceleration, …wall shear stress and instantaneous volume flow rate have been computed and their variations with different parameters have been analyzed. The following important observations have been made: (i) The velocity and acceleration profiles can have more than one maxima, this is in contrast with usual parabolic profiles where they have only one maximum at the axis. As n increases, the maxima shift towards the axis; (ii) For the flow with no body acceleration, the amplitude of both, wall shear and flow rate, increases with n, whereas for the flow with body acceleration, the amplitude of wall shear (flow rate) increases (decreases) as n increases; (iii) In the absence of body acceleration, pseudoplastic (dilatant) fluids, with low frequency pulsations, have higher (lower) value of maximum flow rate Qmax than Newtonian fluids, whereas for high frequencies, opposite behavior has been observed; for flow with body acceleration pulsations gives higher (lower) value of Qmax for pseudoplastic (dilatant) fluids than Newtonian fluids. Show more

Keywords: Power-law fluid, Body acceleration, Pulsatile flow, Finite difference method

DOI: 10.3233/BIR-1990-27510

Citation: Biorheology, vol. 27, no. 5, pp. 747-758, 1990

Authors: Yamamoto, Ryoichi | Sakurai, Naoki

Article Type: Research Article

Abstract: The stress relaxation of the cell wall of pea plants was measured and viscoelastic parameters were obtained according to the stress- relaxation analysis developed by Yamamoto et al. (Plant & Cell Physiol. 1970). The creep process of the cell wall was simulated by a numerical integration using stress-relaxation parameters, because the direct conversion of the stress relaxation process to the creep is impractical. In the conversion, a personal computer was programmed for the Maxwell viscoelastic model with a compiler language. Cell wall creep was measured with a specially constituted apparatus and compared with that calculated by the simulation process. The …results suggested that the creep can be reproduced by a computer simulation using the stress-relaxation parameters. Both creep and stress-relaxation properties of plant cell walls can be analyzed by using a single model. Show more

Keywords: Cell wall, Computer simulation, Creep, Stress-relaxation

DOI: 10.3233/BIR-1990-27511

Citation: Biorheology, vol. 27, no. 5, pp. 759-768, 1990

Authors: Long, Mian | Toyama, Yoshiharu | Dobashi, Toshiaki | Sakanishi, Aldo | Wu, Yun Peng | Oka, Syoten

Article Type: Research Article

Abstract: We measured the electric current dependence of sedimentation curves of swine erythrocytes in a saline solution at the volume fraction of erythrocytes H = 0.091 and 0.220. The sedimentation curve fitted well to the exponential type equation ı = a [ 1 − exp ( − b t ) ] at the upward initial electric current I 0 = 0.50 mA , 1.01 mA and 1.50 mA, where ı is the length of the medium layer at time t , …and a and b are phenomenological parameters. The initial slope v 0 of sedimentation curve was enhanced from 0.68 mm/hr at I 0 = 0 mA to 2.85 mm/hr, 3.87 mm/hr and 5.50 mm/hr at I 0 = 0.50 mA , 1.01 mA and 1.50 mA, respectively, for H = 0.220 . We also made sedimentation measurements of erythrocytes in their own plasma at H = 0.220 and 0.316. Sedimentation curves coincided with the sigmoidal type equation ı = ı ∞ / { 1 + ( t 50 / t ) β } at I 0 = 0 mA and 0.50 mA, where ı ∞ is ı at t → ∞ , t 50 is the time when the plasma level falls to ı ∞ / 2 and β is a constant. The maximum slope v max of sedimentation curve increased from 13.29 mm/hr at I 0 = 0 mA to 18.65 mm/hr at I 0 = 0.50 mA for H = 0.220 . Show more

Keywords: Erythrocyte sedimentation rate, swine blood, saline solution, plasma, DC electric field

DOI: 10.3233/BIR-1990-27512

Citation: Biorheology, vol. 27, no. 5, pp. 769-777, 1990

Authors: Stadler, Achim A. | Zilow, Eugen P. | Linderkamp, Otwin

Article Type: Research Article

Abstract: Blood viscosity in normal adults was measured in glass tubes with diameters of 50, 100 and 500 μ m for a wide range of adjusted feed hematocrits (15-70%). Blood viscosity decreased at each of the adjusted feed hematocrits when going from a 500-μ m tube to a 50-μ m tube. The viscosity reduction increased with increasing hematocrit. The steepness in the hematocrit-viscosity curves decreased with decreasing tube diameter. Erythrocyte transport efficiency (hematocrit / blood viscosity) was calculated to estimate the optimal hematocrit for oxygen transport. Optimal hematocrit averaged 38% in 500-μ m tubes, 44% in 100-μ m tubes and 51% …in 50-μ m tubes. Our results suggest that the strong Fåhraeus-Lindqvist effect at high hematocrits may help to maintain oxygen transport in polycythemic patients as long as the driving pressure is sufficient. Show more

Keywords: Blood viscosity, hematocrit, oxygen transport, red blood cell (RBC)

DOI: 10.3233/BIR-1990-27513

Citation: Biorheology, vol. 27, no. 5, pp. 779-788, 1990

Authors: Lam, Luk S. | Bert, Joel L.

Article Type: Short Communication

Keywords: hyaluronic acid, hydraulic flow conductivity, sedimentation, fluid flow resistance, molecular weight, concentration dependence

DOI: 10.3233/BIR-1990-27514

Citation: Biorheology, vol. 27, no. 5, pp. 789-795, 1990

Authors: Lucas, C.L. | Wilcox, B.R. | Henry, O.W. | Ferreiro, J.I. | Singh, Megha

Article Type: Short Communication

Keywords: Curved tube, Steady flow, Stream line, Attachment point

DOI: 10.3233/BIR-1990-27515

Citation: Biorheology, vol. 27, no. 5, pp. 797-805, 1990

Article Type: Announcement

DOI: 10.3233/BIR-1990-27516

Citation: Biorheology, vol. 27, no. 5, pp. 807-810, 1990

Article Type: Other

DOI: 10.3233/BIR-1990-27517

Citation: Biorheology, vol. 27, no. 5, pp. 811-811, 1990