Experimental Investigation And Numerical Simulation On Deformation And Breakup Of Non-Newtonian Fluid Droplet

The deformation and breakup of the droplet is a phenomenon of fluid movement that occurs after the high-speed jet is far away the nozzle.The deformation and breakup of non-Newtonian viscoelastic droplet is not only ubiquitous in nature but also involves a large number of key technologies in the industry.At present,the previous research on droplet breakup is based on Newtonian fluid.The research involves the definition of the breakup regime and the analysis of the breakup time and deformation degree.The numerical simulation is mainly based on the 2-dimensional grid and the traditional interface capturing method.(Volume of Fluid method and Level-Set method).The numerical interface capturing of the two-phase and small density ratio is studied.In terms of non-Newtonian fluids,because the number of their species is large and they has a nonlinear constitutive relation,there is no universal research conclusion in experimental and numerical investigation.In this paper,the mechanism of deformation and breakup of the carpol solution of viscoelastic fluid is studied experimentally,and the characteristics of droplet breakup are analyzed by numerical simulation.The research content is divided into the following two parts:Firstly,based on the mechanism of droplet breakup,a high-speed imaging experimental platform for droplet breakup was built,and breakup of water and different concentration carpol solution droplets were imaged.According to the experimental results,it can be summarized as the following four points:(1),the concentration of carpol solution will affect the deformation development of the droplet;(2),with the increase of the concentration of carpol solution,the required aerodynamic force for conversion between each breakup regime is gradually enhanced;(3),with the increase of the concentration of carpol solution,the relationship between the initial breakup time Tini and Weber number is no longer consistent with the trend between them of Newtonian fluid.(Tini increases with the increase of Weber number);(4),as the concentration of carpol solution increases,the droplet deformation rate decreases,but droplet displacement WD and(Dwise/D)minincrease,and the variety trend is no longer significant when the strong aerodynamic force acts.Second,based on the multi-phase flow numerical calculation theory,the coupling algorithm S-CLSVOF(simple coupled VOF and LS method)combined with adaptive mesh refinement technology is used to calculate the 3-dimensional interface motion of droplet breakup.According to the numerical simulation results,it can be summarized as the following four points:(1),the droplet deformation and the breakup process are affected by the windward surface airflow and the leeward vortex;(2),The degree of droplet deformation varies with the Weber number and Ohnesorge number is consistent with the experimental results;(3),the increase of the Weber number promotes the growth of the kinetic energy of the droplet,and the increase of the Ohnesorge number hinders the growth of the kinetic energy of the droplet;(4),The increase of the Weber number causes the growth of the radial deformation of the droplet Dcro/D and the drag coefficient Cd to accelerate.The increase of the Ohnesorge number hinders the increase of the two.Combined with the previous empirical formula,the drag coefficient calculation model can predict the force of the droplet during the deformation period.