Direct Numerical Simulations Of The Motion Of Particles In Fluid Flow And Its Application In Microcirculation

Fluid mechanics mainly study the fluid’s state, the interaction between the fluid and solid walls, and the interaction between the fluid and other dynamics under various forces. It has many important applications in the fields of aeronautics, biomedical engineering and mechanics. In this study, we discuss the direct numerical simulation of the motion of particles in a two-dimensional incompressible viscous fluid flow. Firstly, we study the influences of several crucial parameters such as the particle radius, the initial position of the particles in the fluid, the fluid velocity and viscosity on the dynamic motions of the non-buoyant rigid particles in a shear flow. Then we investigate the deformation and dynamics of deformable particles in an irregular-shaped domain(for the case of the motion of erythrocytes in stenotic microchannel). For the dynamics of the rigid particle in shear flow, we simulate the motion of the fluid and the particle through the Navier-Stokes equations and the Euler-Newton’s equations, respectively, and use the fictitious domain method combined with the distributed Lagrange multiplier method to deal with the problems of the numerical simulation of migrations of particles in a fluid flow. For dynamics of the deformable particles in an irregular-shaped flow, we also use the Navier-Stokes equations to describe the motion of the fluid, and apply the Immersed Boundary Methd to deal with the problem of the fluid-cell interaction,then use the fictitious domain method to optimize the calculation area and obtain the control equations. Then we use numerical simulations to verify and analyse the accuracy of the above methods. We find through the numerical experiments that the factors such as non-neutrally buoyant partcle’s radius and fluid viscosity will affect the particles’ equilibrium position in the fluid, and we can also see that when the initial arrangement positions of the erythrocytes in the stenosed vessel are different, it will affect the deformation and dynamics of the erythrocytes. Our study of the dynamics of particles in a flow will have an extensive guidance and practical value in the fields of physics, biomechanics and biomedicine.