Numerical Simulation And Experimental Study On The Deposition Process Of Droplet Impacting Onto The Fabric Surface

Electronic information intelligent textile is a new type textile which highly integrates sensing,communications,artificial intelligence and other high-tech means with traditional textiles,and thus has an important application prospect in the,aerospace,biomedicine,entertainment and health care.However,as the key of flexible integration of electronic information technology and textiles,the conductive circuit is faced with the problems of high cost,complicated process and so on.In this paper,a method of droplet jet printing forming conductive line is presented.The key and difficulty of the technique is to control the droplet’s deformation accurately,because it influences the part forming and precision directly.Based on the above,a method of theoretical analysis combined with numerical simulation is used to study the collision and penetration process of droplets and fabric substrate by the model of droplet impact on fabric substrate,revealing the deposition rule of droplet on fabric surface and laying a theoretical foundation for the subsequent print forming high quality conductive lines.A yarn centerline model is obtained based on the principle of minimum potential energy.A two-dimensional geometric model of the unit cell of the fabric is established by studying the distribution of the fibers in the yarn cross-section and the calculation method of the fiber volume fraction.A two-phase flow model for a single droplet depositing and then deforming on the fabric surface is developed based on the volume of fluid(VOF)method.Using the computational fluid dynamics software FLUENT,the process of the droplet with fabric substrate collision and penetration have been simulated.The changes pressure field and flow field in the deposition process were studied,and the results show that the pressure gradient inside liquid was the main factor resulting in droplet spreading,penetration and bubble formation.The change of the internal flow field is the essence of the change of the shape.The influence of surface tension,viscosity,droplet radius and velocity on the deposition process was investigated by the method of multiple factor analysis,and the results show that the pressure gradient inside liquid was the main factor resulting in droplet spreading,penetration and bubble formation.The change of the internal flow field is the essence of the change of the shape.The amplitude and frequency of the droplet oscillations increase with the decrease of the surface tensionand the viscosity of the liquid and with the increase of the radius of droplet,the smaller the surface tension is,the longer the time of reaching the maximum spreading diameter and the maximum penetration height is.The time required for the droplet to reach the maximum spreading diameter has little to do with the viscosity.The time of the permeation process increases with increasing viscosity,and the rate of penetration decreases with the increase of droplet radius and collision velocity.On the basis of numerical simulation,a self-developed pneumatic droplet drop-on-demand system was used to study the droplet deposition process.The image acquisition system was used to collect the morphological changes of droplet in the collision process and infiltration process,and the results were compared with the simulation results.The results show that the simulation results are in good agreement with the experimental photographs,which proves the correctness of the model.Through the study of the diffusion of the droplet on the fabric surface,the infiltration law of droplet in the fabric is obtained.