The effect of steady flow on transient viscoelastic behavior of blood

The time variation of dynamic rigidity modulus G′ and loss modulus G″ of horse and human bloods was determined at 1 Hz after imposing the steady flow with different shear rates for a fixed period. At hematocrits below 45 %, the values of G′ and G′ increased and then decreased through a maximum, depending on the shear rate of the preceding steady flow. The rates of decrease of G′ and G″ after the maximum were greatest at the shear rate of about 10 sec⁻¹ . The shortening of the duration of imposed steady flow reduced the shear rate dependence of the time variation of G′ and G′. At high hematocrits the rate of decrease of G′ was independent of the shear rate. These observations indicate that the preceding steady flow gives a prolonged influence on the time change of the aggregation structure of red cells during viscoelastic measurement.