Simulation of red blood cell aggregation in shear flow.

A simulation model has been developed for red blood cell (RBC) aggregation in shear flow. It is based on a description of the collision rates of RBC, the probability of particles sticking together, and the breakage of aggregates by shear forces. The influence of shear rate, hematocrit, aggregate fractal dimension, and binding strength on aggregation kinetics were investigated and compared to other theoretical and experimental results. The model was used to simulate blood flow in a long large diameter tube under steady flow conditions at low Reynolds numbers. The time and spatial distribution of the state of aggregation are shown to be in qualitative agreement with previous B-mode ultrasound studies in which a central region of low echogenicity was noted. It is suggested that the model can provide a basis for interpreting prior measurements of ultrasound echogenicity and may help relate them to the local state of aggregation.