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Transient rheological behavior of blood in low-shear tube flow: velocity profiles and effective viscosity
Ist Teil von
American journal of physiology. Heart and circulatory physiology, 1995-01, Vol.268 (1), p.H25-H32
Ort / Verlag
United States
Erscheinungsjahr
1995
Link zum Volltext
Quelle
MEDLINE
Beschreibungen/Notizen
C. Alonso, A. R. Pries, O. Kiesslich, D. Lerche and P. Gaehtgens
Department of Physiology, Freie Universitat Berlin, Germany.
Velocity profiles of human blood flowing through vertical and horizontal
glass tubes (25-100 microns ID) were measured as a function of time
following a sudden reduction of wall shear stress (tau w) from a high value
to values ranging from 2 to 100 mPa. Cell velocities at various radial
positions were determined off-line from video recordings by digital image
analysis. In vertical tubes, symmetric velocity profiles were obtained that
developed increasing bluntness with time, particularly at lower tau w and
in smaller tubes. In horizontal tubes, velocity profiles developed strong
asymmetry as a function of time. Red blood cell (RBC) sedimentation was
associated with uniform low flow velocities in the concentrating cell
sediment, whereas faster flow and almost parabolic profiles were observed
in the supernatant plasma region. Calculations of effective blood viscosity
showed a decrease with time at low tau w in vertical tubes but an increase
in horizontal tubes. The differences between profile shape and effective
viscosity in vertical and horizontal tubes disappeared at tau w > 50
mPa. These findings are related to the cross-sectional distribution of RBC,
which depends on RBC aggregation and sedimentation.