A New Algorithm For Fluid Drag Force Of Particles Based On Disturbance Velocity Correction

With the progress of science and technology,the particle control technology in microfluidic system has developed rapidly.These techniques are serving more and more industrial and daily life.Due to the complexity of flow conditions and the interaction of multiple particles,there still have a lot of innovations and optimization designs to do for particle control technology in microfluidic environment.Among them,the research direction of accurately calculating the fluid viscosity drag force of particles with considering the interaction of multiple particles in microfluidic system has attracted wide attention.Precise fluid drag force is not only helpful to the precision and efficiency of particle manipulation,but also to the more precise and accurate design of particle trajectory.Therefore,it is of great significance and value for the future development of microfluidic particle control technology to study the fluid drag force under the influence of multiple particles.In this thesis,a faster and more accurate algorithm for calculating fluid drag force in multi-particle system is discussed under the condition of Stokes flow to improve the computational accuracy and efficiency of fluid drag force.On the basis of the analytical solution of particle motion in the Stokes flow,a fluid-solid coupling iterative algorithm for a multi-particle,multi-particle size is proposed(ISF method).The effectiveness and accuracy of the algorithm are studied through simulation experiments,and its application range is explored.Finally,the multi-particle sedimentation motion is simulated by using this algorithm.The results show that the ISF method has a good effect on the fluid drag force correction of multi-particle system in small Reynolds number flow.This method can sensitively capture the interaction between particles through the fluid,and the application range of the ISF algorithm is verified to be Re(27)1.Applying ISF method to numerical simulation of particle sedimentation,we found that the falling movement of multiple particles in the stationary fluid will produce the phenomenon of "over-accerlerated" under the mutual influence of each other.The falling velocity will obviously exceed that of the single particle sedimentation.If the particles form an axisymmetrical "long body" structure during the sedimentation process,the "long body" structure can be maintained under the ideal condition of small Reynolds number.When two particles with the same free terminal velocity and different size falling together,the larger particle will have stronger interaction with the smaller particles due to its larger characteristic length.When the same three particles falling side by side,the phenomenon of particle rearrangement may occur due to the difference of initial distance between them,causing the particles with different initial positions become the one left behind.