Force acting on spheres adhered to a vessel wall

Area of Science:

• Fluid dynamics
• Biomedical engineering
• Cellular mechanics

Background:

• Leukocyte adhesion to vessel walls is a critical factor in inflammatory responses and vascular diseases.
• Quantifying the forces acting on adherent leukocytes is essential for understanding their behavior and impact on blood flow.

Purpose of the Study:

• To numerically evaluate the forces (drag and torque) exerted on leukocytes modeled as adhered spherical particles.
• To investigate how particle arrangement and size influence these forces and the apparent viscosity of blood flow.

Main Methods:

• Utilized a finite element method to analyze the flow field around rigid spherical particles adhered to a circular tube wall.
• Modeled adherent leukocytes in single-row and two-row arrangements with regular spacing.
• Calculated drag force, torque, and apparent viscosity as functions of particle-to-tube diameter ratio and arrangement.

Main Results:

• Two-row particle arrangements, especially with alternating placements, resulted in higher drag and torque compared to single-row arrangements.
• Increased particle size and decreased axial spacing between particles further amplified drag and torque.
• Apparent viscosity was significantly elevated in vessels with adhered particles compared to those without or with freely floating particles.

Conclusions:

• Leukocyte arrangement significantly impacts the forces experienced by individual cells and the overall rheology of blood flow.
• Adherent leukocytes substantially alter blood flow properties, potentially exacerbating conditions like inflammation and thrombosis.
• The study provides a quantitative framework for understanding the biomechanical consequences of leukocyte adhesion in microcirculation.