Dynamic Behavior Of Active Particle Systems In Polygonal Barrier Environments

Active particles,also known as self-driving particles,are entities that consume internal energy to produce motion,usually associated with moving microorganisms,artificial particles,and swarms of animals.The self-drive movement of active particles is very common in nature.from small to micro world,the transport of molecular motor proteins in microtubules,to macro world,the aggregation of fish,sheep and even people.the physical models that simulate such particles are the swimming steering particle（rtp）model and the active brownian particle（abp）model,respectively.In these systems,there are directional movements and large fluctuations.It is inevitable to encounter obstacles in the actual moving place and application of active substances.Therefore,the dynamic behavior of active particle system in obstacle environment has attracted the interest and research of scientific research and colleges at home and abroad.In this work,the dynamic behavior of active particles in polygonal obstacle environment composed of non-active particles is studied by molecular dynamics simulation.The main contents of this thesis are as follows:In the introduction of the first chapter,the active particles and their kinetic behavior are first introduced,and then the related research progress at home and abroad is briefly summarized.Finally,the simulation methods——molecular dynamics used in this paper are briefly introduced.In the second chapter,the motion of the active particle system around various convex polygon obstacles is studied.The polygon barrier is composed of inactive particles,fixed in the whole simulation process,and the active particles are uniformly distributed around the obstacle.the influence of obstacle size,obstacle edge number（curvature）,active particle activity force size and rotational diffusion coefficient on its dynamic behavior is discussed in detail.By analyzing the velocity flow distribution of the active particles around the obstacle,the image of the angle of the active particles with time,the graph line of the accumulation angle of the active particles with time and the probability distribution of the absolute value of the angular velocity,the motion of the system is divided into three types:directional rotation,transition state,and undirected rotation.In chapter Ⅲ,the kinetic behavior of active particles in special polygonal（concave polygon——hexagonal）obstacle environments is investigated.the influence of obstacle size,obstacle edge number（curvature）,active particle activity force size and rotational diffusion coefficient on its dynamic behavior is discussed in detail.It is concluded that the system can undergo long-term and stable directional rotation under certain parameter conditions and certain obstacle size.In the fourth chapter,the research work of this paper is reviewed and summarized,and the following research work is also prospected.