Experimental And Numerical Study On Deformation And Breakup Of Droplets Under Shock Wave

The deformation and breakup of droplets in high-speed airflow is a typical multiphase fluid mechanics problem,the interaction between the shock wave and the liquid drops can also cause the typical Richtmyer-Meshkov(RM)instability,the research on the deformation and fragmentation of liquid droplets under shock wave has many engineering and scientific application value,such as supersonic raindrop erosion,combustion and explosion of multiphase mixtures,liquid atomization and so on.In this paper,the experimental research on the deformation and breakup of liquid droplets in high-speed airflow is carried out in the shock tube,and the numerical calculation of the interaction between shock wave and droplet is studied.In this paper,the interaction between shock and droplet is studied in vertical shock tube and horizontal shock tube,a wide range of shock Mach numbers is produced by the electrothermal rupture method(Ma=1.28-4.04),the process of deformation and fragmentation and morphological features of the droplets under the action of shock waves were obtained by using high-speed camera direct shooting and laser shading method combined with high-speed camera,the displacement of liquid droplets,lateral deformation and axial deformation with time were analyzed quantitatively.,the influence of droplet viscosity on the deformation and breakup of droplet is also analyzed.The numerical simulation was carried out by using CFD software such as Gambit and Fluent.By using multiphase VOF model and k-? turbulence model,two-dimensional numerical simulation of the deformation and breakup process of water droplets and electron fluoride droplets in different gas phases was carried out,and the physical properties of the droplet and the surrounding flow field after shock wave interaction with the droplet are obtained,further analyzed the deformation and breakup mechanism of the droplet under the impact of shock wave.Through the analysis of experimental results and numerical simulation results,we got following conclusions:After the shock wave passes through the liquid drop,the droplets are subjected to two main stages of deformation-peeling and breakup,the deformation and breakup modes of different viscous droplets under shock wave are stripping broken.The smaller the surface tension of droplets,the easier the deformation of the droplets,and the faster the rate of deformation and breakup.In the process of deformation and breakup of droplets,the greater thegas-liquid density ratio is,the easier the deformation and broken of the droplets is,which is the instability factor.In the case of different droplet viscosity,the initial acceleration values of droplets are similar to a constant,and the initial acceleration of the droplet is an increasing function of the shock wave Mach number,and the acceleration of the droplet tends to decrease with the increase of the droplet viscosity.The lateral deformation of the droplet undergoes the nonlinear process of first increasing and then decreasing,axial deformation is a process of first decreasing and then increasing,the maximum value of the lateral deformation of the droplet increases with the initial droplet diameter,and increases with the increase of the shock Mach number,the size of the lateral deformation of the droplet increases first and then decreases with the increase of the droplet viscosity.The greater the viscosity of droplets,the later the deformation and breakup of droplets,the deformation and breakup of droplets decreases with the increase of liquid viscosity,which indicates that viscosity always plays an inhibitory role in the process of droplet breakup.The phenomenon of deformation instability appears on the windward side of the droplet under the action of the backward airflow,and developed the "spike" structure,the lower the viscosity of droplets,the faster the development rate of RM instability,and the number of spikes increases first and then decreases with the increase of viscosity.The pressure,velocity and vorticity obtained by numerical simulation have similar trends,but the rate of change is different,the numerical simulation results are consistent with the experimental results in the droplet deformation stage,but there are obvious differences in the stripping fragmentation stage.