Study On The Effect Of Solid Wall Wettability On Droplet Collision Dynamics Behavior

It is of great theoretical and engineering significance to explore the influence of solid wall wettability on the dynamic behavior of droplet collision for guiding the enhancement of gas-liquid separation process,as well as the design and performance improvement of petroleum and petrochemical equipment.In this paper,a droplet collision experimental system was constructed.Combined with the numerical simulation method of Coupled Level Set and Volume of Fluid,the deformation behavior and motion characteristics of droplets on the different wettabilities substrates are systematically analyzed from the dynamic behavior of single droplets impacting different wettabilities substrates.and then reveal the mechanism of collisional coalescence behavior of double droplets on substrates with different wettability.On the basis of the obtained homogeneous droplet collision behavior law,the analysis of collision dynamic behavior of compound droplets with entrapped solid particles at different wettabilities substrates is carried out.To reveal the influence law of wettability on the collision behavior of single droplet,double droplet and compound droplet,which provides reference and foundation to guide the design of related industrial equipment,industrial process strengthening and substrate modification design.The experimental study was carried out for single droplet impact on substrate with different wettability by high-speed camera equipment,and the effects of substrate contact angle,substrate inclination angle and collision Weber number on the deformation behavior of droplet collision were systematically analyzed.By analyzing the experimental results,the droplet collision process is divided into four characteristic stages: spreading,retraction,oscillation and stability,The influence laws of different experimental variables on the dynamic process of droplet collision and the deformation evolution laws among the characteristic stages are revealed.The influence law of substrate wettability and collision Weber number on the breakage phenomenon was obtained,and the critical Weber number relationship curves of droplet breakage under different substrate contact angle conditions were obtained.Based on the CLSVOF method to analyze the process of head-on collision between double droplets on different wettability substrates.The experimental phenomenon of double droplet collision coalescence is analyzed by combining the variation laws of internal pressure field and velocity field.The formation process,causes and distribution range of air entrainment,complete bounce and partial bounce phenomena during droplet collision are investigated.The mechanism of the different phenomena is explained by combining the velocity vector distribution and pressure distribution inside the droplet as well as the nature of each experimental variable,and the Weber number and contact angle distribution ranges for the different phenomena are derived.A compound droplet preparation method with internally entrapped solid particles is proposed by combining the homogeneous droplet collision dynamic behavior law.carrying out the analysis of the dynamic behavior of compound droplets impacting on substrates with different wettability.Four kinds of characteristic collision,namely adhesion collision,complete bounce collision,partial bounce collision and breakup collision,are defined when the compound droplet impacts the substrate with different wettability in combination with the dynamic process.The four collision types were compared with the homogeneous single droplet collision process to reveal the behavior pattern of the compound droplet collision process influenced by the internal solid particles.The influence law of different collision heights and substrate contact angles on the maximum spreading diameter and maximum jet height of compound droplets was obtained.