Biorheology - Volume 24, issue 5

Authors: Zeggwagh, G. | Bellet, D.

Article Type: Research Article

Abstract: A theoretical study concerning two-component fluid pulsating flow through porous conical ducts is presented. The model corresponds to blood flows through small diameter porous conical vessels. This approach is based on a finite difference method. The physical hypothesis used were based on findings from simultaneous visualization methods. The influence of geometrical, hydrodynamical and structural parameters is systematically examined and related to velocity profiles, hydrostatic pressure.

Keywords: Hemodynamics, microcirculation, plasmatic layers, porous conical tubes, hematocrit rate, Quemada law

DOI: 10.3233/BIR-1987-24501

Citation: Biorheology, vol. 24, no. 5, pp. 427-440, 1987

Authors: Khodabandehlou, T. | Lelièvre, J.C. | Joly, M.

Article Type: Research Article

Abstract: The tangent simple systems (TSS) method, proposed in (1), is applied in order to study the viscoelastic behaviour of human blood in transient flow for a rectangular low shear rate step. The tangent simple systems which were used are Maxwell liquids. These systems allow one to obtain plots of variations of instantaneous values of viscosity coefficient μ , elasticity modulus G and retardation time τ =μ /G of the studied blood samples, as a function of flow duration. Variations of both parameters μ and G versus time are represented by two exponential functions which involve three couples of parameters …(μ 0 , μ ∞ ), (G0 ,G∞ ) and (τ μ ,τ G ). These parameters can be considered as the characteristics of each blood sample. Another representation of the results, called the dual rheogram, is also indicated. The dual rheogram enables one to follow the evolution of the blood structure. Several examples of application of the TSS method to normal blood sample and to suspensions of artificially modified red blood cells (RBC) are given. Show more

Keywords: Blood Viscoelasticity

DOI: 10.3233/BIR-1987-24502

Citation: Biorheology, vol. 24, no. 5, pp. 441-449, 1987

Authors: Boynard, M. | Lelièvre, J.C. | Guillet, R.

Article Type: Research Article

Abstract: The erythrocyte aggregation phenomenon is an important factor in capillary circulation. This phenomenon can be evaluated by a number of methods (microscopic observations, viscometry, light measurements) which cannot be applied simply to in vivo measurements. In contrast, ultrasound which propagates through soft tissues allows measurement of the mechanical properties of red blood cell (RBC) suspensions which depend on the aggregation phenomenon. We devised an apparatus in order to measure in vitro the ultrasonic backscattering intensity of RBC suspensions. First, with latex particules of different sizes, the ultrasonic backscattering coefficient has been measured in order to evaluate the apparatus response. Then, …the ultrasonic backscattering coefficient of different aggregated erythrocyte suspensions has been measured and correlated with the erythrocyte sedimentation rate. Finally, the size of RBC aggregates of different suspensions has been evaluated. Show more

Keywords: Aggregation, Red Blood Cell, Ultrasound, Backscattering

DOI: 10.3233/BIR-1987-24503

Citation: Biorheology, vol. 24, no. 5, pp. 451-461, 1987

Authors: Neumann, F.-J. | Schmid-Schönbein, H. | Malotta, H.

Article Type: Research Article

Abstract: As the temperature dependence of relative apparent whole blood viscosity η rel is still controversial, the relation between the temperature dependence of red cell aggregation (RCA) and that of η rel was examined in normal donors and in patients with venous ulcers of the leg. Apparent whole blood viscosity was measured in the DEER-rheometer (0.01Pa < τ < 2.9Pa) at 10°C, 20°C, 30°C and 37°C. The instrument was calibrated for each temperature to correct for changes in viscometer geometry. Simultaneously the minimal shear stress τ Tmin to keep RCA dispersed was determined by photometric aggregometry. η …rel was found to increase with decreasing temperature. By basing the relative cold induced increase in η rel on the state of RCA as defined by the ratio of τ /τ Tmin the relation between both features is verified: With increaslng RCA the cold induced increase in η rel is progressively enhanced. Show more

Keywords: viscosity, red cell aggregation, temperature, erythrocyte

DOI: 10.3233/BIR-1987-24504

Citation: Biorheology, vol. 24, no. 5, pp. 463-472, 1987

Authors: Hocking, M.B. | O’Brien, R.N.

Article Type: Research Article

Abstract: Erythrocytes were settled from whole blood in standard 200 × 2.5 mm erythrocyte settling rate tubes placed vertically and at various angles from 85° to 15° from the horizontal. In all cases sedimentation rates measured along the slope increased with decreasing angle from the horizontal. Vertical settled distances rapidly increased down to an angle of 70° and then changed very little even down to angles as shallow as 30°. Evidence is presented that convection plays a significant role in the inclined settling of erythrocytes, as has already been demonstrated with clay, or glass bead suspensions in water. Inclined settling enhancements obtained are …quite similar to those observed under similar conditions with yeast cells in aqueous glucose. Show more

Keywords: Inclined sedimentation rate, convection, erythrocyte

DOI: 10.3233/BIR-1987-24505

Citation: Biorheology, vol. 24, no. 5, pp. 473-482, 1987

Authors: Nandy, S. | Tarbell, J.M.

Article Type: Research Article

Abstract: Wall shear stress has been measured by flush-mounted hot film anemometry distal to an Ionescu-Shiley tri-leaflet valve under pulsatile flow conditions. Both Newtonian (aqueous glycerol) and non-Newtonian (aqueous polyacrylamide) blood analog fluids were investigated. Significant differences in the axial distribution of wall shear stress between the two fluids are apparent in flows having nearly identical Reynolds numbers. The Newtonian fluid exhibits a (peak) wall shear rate which is maximized near the valve seat (30 mm) and then decays to a fully developed flow value (by 106 mm). In contrast, the shear rate of the non-Newtonian fluid at 30 mm is …less than half that of the Newtonian fluid and at 106 mm is more than twice that of the Newtonian fluid. It is suggested that non-Newtonian rheology influences valve flow patterns either through alterations in valve opening associated with low shear separation zones behind valve leaflets, or because of variations in the rate of jet spreading. More detailed studies are required to clarify the mechanisms. The Newtonian wall shear stresses for this valve are low. The highest value observed anywhere in the aortic chamber was 2.85 N/m2 at a peak Reynolds number of 3694. Show more

Keywords: Heart valve, wall shear stress, hot-film anemometry, non-Newtonian fluid, pulsatile flow

DOI: 10.3233/BIR-1987-24506

Citation: Biorheology, vol. 24, no. 5, pp. 483-500, 1987

Authors: Isogai, Yukihide | Yokose, Takuo

Article Type: Abstract

DOI: 10.3233/BIR-1987-24507

Citation: Biorheology, vol. 24, no. 5, pp. 501-532, 1987

Article Type: Other

DOI: 10.3233/BIR-1987-24508

Citation: Biorheology, vol. 24, no. 5, pp. 533-533, 1987