Numerical Simulation Study On Particle Behavior Under Electrostatic Effects In Bifurcated Tube

In recent years,with the gradual increase of respiratory diseases,which seriously endanger human health and normal life,inhalation therapy has become more and more important means to treat respiratory diseases,and the effective delivery of drugs in the respiratory tract is an important guarantee for the therapeutic effect.As we all know,the bifurcated airway of the human respiratory system is a typical bifurcated network structure,and most of the inhaled particles are charged.Therefore,it is of great significance to study the effect of electrostatic effects on particle motion in bifurcated tubes.This paper aims to provide a theoretical basis for drug inhalation therapy and effectively improve the treatment efficiency of respiratory system diseases by studying the movement characteristics of charged particles in the bifurcated tube of the human body.The work of this paper is based on the accurate calculation of the flow field,coupled with the Lagrangian particle trajectory tracking method,to analyze the fluid flow characteristics and particle motion behavior in the bifurcated pipe.Through the electrostatic calculation between particles,the behavior of particles with and without electrostatic effects is compared,and the influence of electrostatic effect on the movement of particles in the bifurcated tube is analyzed.Firstly,based on the bifurcated airway structure of the human respiratory system,a symmetrical single bifurcated tube geometric model is established in this paper,and the gas-phase flow field in the bifurcated tube is obtained by simulation.The results show that the interaction between curvature and shunt effect results in a pressure gradient in the non-flow direction,resulting in the formation of secondary flow.In the sub-tube section,the fluid produces a pair of vortices that are vertically symmetrical and counter-rotating,namely Dean vortices,and they move backward along sections,and the position of the vortices moves from the outer wall of the pipe near the top to the horizontal centerline.In the bifurcated tube,the velocity of the flow field is symmetrically distributed along the centerline of the mother tube,and its maximum velocity extends to the inner wall of the sub-tube in turn along the centerline of the mother tube.The closer to the exit end of the sub-tube,the smaller the area of maximum velocity.Low speed high pressure region is generated at the ridge.Near the inner wall of the sub-tube,the development of the axial velocity appears as a high-speed crescent region.Secondly,in this paper,uncharged particles are added to the flow field that has reached a statistical steady state,the motion behavior and distribution characteristics of particles with three different particle sizes(d_p=10μm,20μm,50μm)are calculated.The influence of fluid structure on particle transport mechanism and the influence of particle size change on particle distribution and motion behavior were explored.The results show that the small particles have better flowability and stronger diffusivity.For particles with d_p=10μm and d_p=20μm,under the action of the secondary flow of the fluid,the particles form a“V”-shaped particle low concentration area near the ridge,and a“particle void region”is formed on the sections of the sub-tube.For particles with d_p=50μm,the gravity effect of large particles causes a large number of particles to aggregate on the inner wall of the tube,resulting in the disappearance of the“V”-shaped particle low concentration area,and gravity completely destroyed the vortex structure constraint of particles.The“particle void region”disappears,at this time the particles pass through the vortex and are uniformly distributed in the area outside the inner wall of the tube.Finally,this paper considers the influence of electrostatic effects on gas-solid two-phase flow in bifurcated tube.Similarly,charged particles are added into the flow field above,and the movement of uncharged particles is compared and analyzed to study the influence of electrostatic force on particle movement behavior and distribution characteristics.The results show that with the increase of particle size,the influence of electrostatic force on particle motion is more significant.The distribution of electrostatic field changes with the movement of particles.The electrostatic force accelerates the diffusion movement of particles,and the repulsive force between the particles makes the aggregated particles disperse,so that the particle concentration at the tube wall is significantly reduced,and the“particle void region”is reduced.In addition,electrostatic force also promotes the influence of fluid structure on particle motion,accelerates the development of charged particles following secondary flow motion,and enhances the effect of particle response to vortices.In this paper,by studying the movement of particles in bifurcated tube under electrostatic effects,it is found that the electrostatic effects between particles in the bifurcated tube can make the drug particles reach specific parts of the human body faster,avoid local aggregation of particles,thus shortening the treatment time of inhalation therapy and improving the treatment efficiency,which has important practical significance.