Research On Movement Characteristics Of Axial Release Filament (Bundle) Subjected To Fluid Traction

In this paper,the interaction model of airflow and weft was modeled as the fluid-solid coupling dynamics of a class of variable length filament(bundle),Combining with Momentum Exchange(ME),Immersed Boundary Method(IBM)and lattice Boltzmann Method(LBM),that was ME-IBM-LBM method.The dynamic response characteristics of a class of variable length filament in a flow fieldwere studied for the first time,and the morphology of the bundle(yarn)at different release speedswasrecorded,then,a good consistency between the non-periodic oscillation and numerical simulation was obtained.The research work of the thesis has a strong guiding value for the airflow insertion.Meanwhile,the research method and technical route can also provide some references for other dynamic behaviors,such as the ship rope haulage,the movement conveyor belt,the ocean cable structure and the rope system satellite's release and recovery,the aerial tanker refueling tube.The specific work of this paper is:(1)In the fluid computing domain,LBM was used to realize the evolution process of collision and migration,and a two-dimensional incompressible viscous fluid based on LBM calculation model was constructed.At the same time,finite difference method was used to solve the motion equation of one-dimensional flexible body.The increase of the physical length of the flexible body(that was,the increase of the solid unit)was calculated by preserving the Taylor series of first-order accuracy.Fluid solution results and solid solution results were obtained by means of IBM method to realize boundary coupling in the solution process of fluid-solid coupling boundary.(2)The Poiseuille flow was simulated by LBM method,and the corresponding numerical solution was obtained,but more than that,the results are very consistent with the analytical solution.Then,in the classical numerical simulation of circular flow,the two-step rebound format and ME-IBM-LBM method were used to calculate the coupling boundary,analyzing the different motion patterns of fluid in different situations of 20,40,100,200 and calculating the lift coefficient CL,drag coefficient CD and pressure coefficient CP which were consistent with existing literature data.The phenomenon of karman vorticity was obtained when the Reynolds number was 100 and 200.(3)Firstly,the interference between the fixed-length flexible fiber(it was also called filaments in the relevant literature.In this paper,it was called fiber)and the flow field was simulated and analyzed,as the relationship between the length L and the amplitude of the flexible fiber was obtained,which verified the stability and feasibility of the program.Then,the motion process of the axial release filament subjected to fluid traction was calculated by using the ME-IBM-LBM method,and the dynamic characteristics of the axial release filament were analyzed at different release speeds and different densities.It was found that when the flexible fiber density was 0.2,it was finally stationary.When the density was greater than 0.2,the maximum amplitude is proportional to the density and the release velocity.That was,as the release velocity and density increased,the amplitude increased.And the velocity is decreasing and the final velocity is close to 0 based on the velocity and displacement phase diagram which was perpendicular to the tail of the flow.To sum up,variable length filament had two types of motion in the fluid,one was the steady-state motion,and the other was a non-periodic oscillation with a larger amplitude.The transition between these two forms of motion was combined by the critical release velocity and the critical density.(4)Establishing the experimental platform of air flow insertion and recording the process of releasing from 10 mm to 100 mm during the three release speed.And the influence factors of yarn in flight were investigated by analyzing the results of experiment.It is found that instability occurs at low speed and high line density,theincreased critical length Lc and the maximum amplitude(including maximum Amax and minimum Amin)of the 50/1 and 40s/1combined filament were inversely related.The vibration amplitude was smaller and smaller,and the motion was relatively stable.As the line density increasesd,the 30s/1 and 20s/1 occured the unsteady motion.This was consistent with the non-periodic oscillation of the flexible filament in the numerical calculation results,and the reliability of the numerical simulation was verified from the side.