Numerical Simulation Of The Active Particle Brownian Motion Based On Lattice Boltzmann Method

Self-propelled Janus particle is the artificial active micro/nano-materials with the potential application of the fields of micro-power and nano-motor.In this paper,based on the fluctuation lattice Boltzmann method,the numerical simulation method and the motion of single Janus particle are studied.As the motion of Janus particle is the coupled motion of self-propulsion and Brownian motion,the essence of whose motion is the superposition of self-propulsion and Brownian motion,which also determines that the numerical simulation of Brownian motion is the basis and prerequisite for the exploration of the Janus particle motion mechanism.In addition,in order to better control the particle motion and considering the limitation of the preparation process,the actual shapes of the Janus particles are not limited to the sphere.Therefore,different shapes of particles are also considered in the numerical study of Brownian motion.Firstly,the Brownian motion of spherical and non-spherical particles are simulated by using the fluctuating lattice Boltzmann method.Comparing the spherical particle simulation results with theoretical and experimental values,the validity of the FLB model has been verified.The Brownian motion characteristics of non-spherical particles with different shapes,including ellipsoidal and cylindrical particles with different aspect ratios,are also studied,and indicate although the non-spherical particles are anisotropic,they still obey the energy equalization theorem.The autocorrelation functions of the velocity and angular velocity of the non-spherical particles obey the“long-time tail”effect,and the velocity autocorrelation function is only related to the particle mass and not affected by the particle shape.In addition,even though the aspect ratio of particle is low,the diffusion coefficient is insensitive to the shape.These findings further lay the foundation for the study of the movement of Janus particles based on Brownian motion.Secondly,in order to shorten the simulation time and reduce the calculation cost,we try to modify the boundary scheme in the model,and use the interpolation bounce-back scheme instead of the half-way bounce-back scheme in the previous model.The applicability of the BFL scheme is verified by the example of the Stokes flow.After comparing the accuracy among the BFL scheme,YMS scheme and LBB scheme,it is found that the YMS scheme has higher accuracy under the same conditions.In addition,the FLB model in the YMS scheme is used to simulate the Brownian motion of spherical particle Brownian motion,and verify its stability and accuracy.Finally,we make the simulation of the motion of Janus particle in the dilute H₂O₂solution with reference to experimental parameters as reported in Zheng.In the simulation,we obtain the mean-square displacement of Janus particles,comparing the simulation results with theoretical values and experimental values,and find that they have a good match.This result illustrates that the FLB model can be used for further study of Janus particle,and proves the applicability of the formula of mean-square displacement proposed by Howse et al.