Viscosity Modeling for Blood and Blood Analog Fluids in Narrow Gap and High Reynolds Numbers Flows

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Computational Modeling

Background:

• Ventricular assist device (VAD) simulations typically use single-phase flow models for blood.
• Blood is a multiphase fluid; cell migration creates heterogeneous distributions, impacting flow dynamics.
• A cell-free layer forms in narrow gaps (<300 μm) due to cell migration, a factor often ignored in VAD simulations.

Purpose of the Study:

• To introduce a novel viscosity model that incorporates cell migration in microchannels relevant to VAD conditions.
• To develop a model accounting for the cell-free layer phenomenon in multiphase blood flow.
• To enhance the accuracy of computational fluid dynamics (CFD) simulations for VADs.

Main Methods:

• Developed a local viscosity model based on measured particle distributions in microchannels using a blood analog fluid.
• The model considers local particle/cell distribution and the formation of a cell-free layer.
• Validated the model by comparing simulation results with experimental data on wall shear stresses and pressure losses.

Main Results:

• The developed viscosity model accurately predicts flow behavior in microchannels with cell migration and cell-free layers.
• The model shows strong agreement with experimental data for both blood and analog fluid flows.
• Demonstrated applicability for particle volume fractions up to 5%, gap heights of 150 μm, and Reynolds numbers around 100.

Conclusions:

• The new viscosity model significantly improves VAD simulation accuracy by accounting for local viscosity variations due to cell migration.
• This approach moves beyond single-phase assumptions, providing a more realistic representation of blood flow in VADs.
• Future work aims to extend the model for physiological particle volume fractions up to 40%.