Accelerating 3D DLM/FD method for simulating the relative motion and migration of spheres and ellipsoids under shear flow condition

• Main Authors: Bo-Wei Lin, 林柏維
• Other Authors: 張建成
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/yncn53

碩士 === 國立臺灣大學 === 應用力學研究所 === 107 === In natural environment and engineering applications, the behavior of particles moving in a fluid is a very important characteristic, such as the flow of cells in the blood, or the effect of mixing drug solutions, etc. This paper simulates two particles in the boundary shear flow using a distributed Lagrangian multiplier/virtual domain (DLM/FD) combined with the Stocks equation and Euler-Newton''s equations. Movement distribution of spherical and ellipsoidal particles in three-dimensional flow field. The main results of this research are three. Firstly, the distance between two particles is calculated by introducing the position of the spherical parameter into the Newton iteration method to accelerate the calculation speed. Then the DLM/FD method is used to simulate the relative motion of spherical and ellipsoidal particles in the shear flow. And finally compare the difference between the two particles in the shape of the movement. The error between the two-particle distance calculation methods is about -3.015%, the difference is not large, the time is reduced by 50-75%, and the speed is effectively improved. In the simulation results, the particle shape is mainly spherical and ellipsoidal, and the initial position, radius and wall distance are changed to simulate the trajectory of the two particles flowing under each condition, so as to achieve the effect of controlling the particle flow pattern. In the simulation results of the two spheres, it can be found that when the flow trajectory is controlled, the effect of changing the initial position and the wall distance is obviously changed. The smaller the wall distance and the closer the distance between the two spheres is easier to exchange trajectory than the radius is changed. In the results of the two ellipsoids, another roll transition trajectory will appear, but it is less controllable. The timing of the exchanged and non-exchanged trajectories is similar to the result of the two spheres. In the multi-sphere simulation results, if the radius is randomly changed, Exchange trajectories are more likely to occur.