Rheological and dynamical characterization of blood analogue flows in a slit

Abstract

Thrombus formation and haemolysis are blood destructive phenomena depending on the flow hydrodynamics, particularly the shear stresses. This work addresses this issue by characterizing experimentally (using the micro-PIV technique) and numerically (using CFD) steady-state Newtonian (water and water/glycerine solutions) fluid flows and non-Newtonian (water/glycerine/xanthan) blood analogue flows, in a slit with a height of 1.3mm and a width of 30mm. The results obtained may provide useful information in the design of extracorporeal devices manipulating blood for diagnosis and therapeutics. Results from CFD showed that the Herschel–Bulkley viscosity model yields velocity predictions in excellent agreement with the experimental data obtained with the micro-PIV. Viscosity measurements evidenced that the water/glycerine (35% w/w)/xanthan (0.02% w/w) solution mimics well the blood global viscosity, exhibiting velocity profile shapes in fully developed flows flattened at the centre, typical of shear-thinning fluids. The maximum shear stresses obtained experimentally (1.39–3.11Pa) for the blood analogue flows at the studied rates (6.7–25.3L/h) evidence that haemolysis is unlikely to occur since lysis threshold values are 150Pa for erythrocytes, 10Pa for leucocytes and 7.5Pa for platelets. However, the smallest flow rate cases may be of concern in blood circulation by yielding clot formation near the walls since the shear stresses there are bellow the thrombus/coagulation threshold (1.0–1.8Pa).