SPH-DEM approach to numerically simulate the deformation of three-dimensional RBCs in non-uniform capillaries.
BACKGROUND
Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries.


METHODS
An elastic spring network based on the discrete element method (DEM) is employed to model the three-dimensional RBC membrane. The haemoglobin in the RBC and the plasma in the blood are modelled as smoothed particle hydrodynamics (SPH) particles. For validation purposes, the behaviour of a single RBC in a simple shear flow is examined and compared against experimental results. Then simulations are carried out to predict the behaviour of RBCs in a capillary; (i) the motion of five identical RBCs in a uniform capillary, (ii) the motion of five identical RBCs with different bending stiffness (Kb) values in a stenosed capillary, (iii) the motion of three RBCs in a narrow capillary. Finally five identical RBCs are employed to determine the critical diameter of a stenosed capillary.


RESULTS
Validation results showed a good agreement with less than 10% difference. From the above simulations, the following results are obtained; (i) RBCs exhibit different deformation behaviours due to the hydrodynamic interaction between them. (ii) Asymmetrical deformation behaviours of the RBCs are clearly observed when the bending stiffness (Kb) of the RBCs is changed. (iii) The model predicts the ability of the RBCs to squeeze through smaller blood vessels. Finally, from the simulations, the critical diameter of the stenosed section to stop the motion of blood flow is predicted.


CONCLUSIONS
A three-dimensional spring network model based on DEM in combination with the SPH method is successfully used to model the motion and deformation of RBCs in capillaries. Simulation results reveal that the condition of blood flow stopping depends on the pressure gradient of the capillary and the severity of stenosis of the capillary. In addition, this model is capable of predicting the critical diameter which prevents motion of RBCs for different blood pressures.
School of Chemistry, Physics and Mechanical Engineering, Faculty of Science and Engineering, Queensland University of Technology, 2-George Street, Brisbane, QLD, 4001, Australia.
Hasitha-Nayanajith
HN
Polwaththe-Gallage
School of Chemistry, Physics and Mechanical Engineering, Faculty of Science and Engineering, Queensland University of Technology, 2-George Street, Brisbane, QLD, 4001, Australia.
Suvash C
SC
Saha
School of Chemistry, Physics and Mechanical Engineering, Faculty of Science and Engineering, Queensland University of Technology, 2-George Street, Brisbane, QLD, 4001, Australia.
Emilie
E
Sauret
Research and Development, Australian Red Cross Blood Service, Kelvin Grove, QLD, 4059, Australia.
Robert
R
Flower
School of Chemistry, Physics and Mechanical Engineering, Faculty of Science and Engineering, Queensland University of Technology, 2-George Street, Brisbane, QLD, 4001, Australia.
Wijitha
W
Senadeera
School of Chemistry, Physics and Mechanical Engineering, Faculty of Science and Engineering, Queensland University of Technology, 2-George Street, Brisbane, QLD, 4001, Australia. yuantong.gu@qut.edu.au.
YuanTong
Y
Gu
D001783:Blood Flow Velocity; D002196:Capillaries / Q000502:physiology; D003198:Computer Simulation; D004907:Erythrocyte Deformability; D004912:Erythrocytes / Q000166:cytology*; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D008833:Microcirculation; D008955:Models, Cardiovascular; D009038:Motion; D015203:Reproducibility of Results
Blood flow; Computational biomechanics; Critical diameter; Discrete element method; Meshfree method; Multiple red blood cells; Smoothed particle hydrodynamics