Fig 1.
Simulation of blood flow in a microvascular bifurcation using the proposed open boundary conditions.
The simulation domain is subdivided into three regions: (A) generating region with fully developed flow; (B) the main simulation domain; (C) the outlet region where particles are deleted. Fluid particles and frozen wall particles are not shown for clarity.
Fig 2.
Schematic illustration of the computational domain of an open system.
The generating region is divided into zones: zones A2 and A3 are sources of ghost particles while zones A1 and A4 are used for placing ghost particles. As soon as a particle crosses the copy border, its copy is created. There is one way interaction between particles in the generating region and particles in the main simulation domain.
Fig 3.
Verification of the accuracy of the proposed method.
(a) Velocity profiles in the cross-flow (x-axis) direction of the Poiseuille flow corresponding to open boundary conditions. The incompressible Navier-Stokes solution is shown with lines. (b) Pressure profile for the Poiseuille flow along the flow (z-axis) direction. The symbols represent the DPD simulation results and the solid line represents the analytical solution.
Fig 4.
Validation of the open boundary conditions.
Typical velocity profiles of blood flow in microtubes at Ht = 15.0% and 30.0%. The simulation results are compared to those in periodic systems at same hematocrit levels. x and z represent the radial and axial distances for the cylinder geometry; vz is the velocity along the flow direction.
Fig 5.
Particle recovery efficiency with respect to flow rate ratio.
(a) Particle recovery efficiency at different hematocrit levels. Two snapshots of the RBCs at microvascular bifurcations with flow rate ratios of 2.5 and 4.0 at Ht = 45.0% are shown. Simulation data (black squares) from [32] are shown. (b) Particle recovery efficiency at different levels of coarse-graining of the MS-RBC model at Ht = 15.0%. The simulations are conducted using the MS-RBC model with Nv = 500, 2560 and 5000.
Fig 6.
Effect of bifurcation angle on particle recovery efficiency.
(a) A sketch of the microvascular bifurcation model by changing the bifurcation angle θ. In this model, the diameter of the parent branch is 20.0 μm, and the diameters of two daughter branches are both 16.5 μm. The average velocity of blood flow in parent branch is about 0.12 mm/s. (b) Relationship between the particle recovery efficiency and bifurcation angle.
Fig 7.
Snaphot for simulation of the blood flow in part of arterial network with three inlets and multiple outlets.
The complex microvascular network was constructed using an angiogenesis model [49]. The walls of the microvascular network were formed by stationary DPD particles. An extra bounce-back reflection was applied to fluid particles to prevent them from entering the solid wall domain.