| The deformation and breakup of a liquid drop under the shock wave impact is not only a fundamental problem of multiphase flow but also with rich engineering backgrounds.In this paper,a combination of experimental observations and numerical simulations are used to explore the deformation and breakup processes of liquid droplet under the action of shock wave,the influence of shock wave strength on the evolution of droplet breakup morphology are revealed with theoretical analysis.The main works and conclusions include are as follows:1.The droplet deformation and breakup experiments are systematically performed through using the shock tube,the deformation and breakup process of droplet under the action of shock wave are observed through high-speed photography.The experimental images clearly show the morphological evolution of droplet deformation and breakup process under different conditions of shock Mach number and droplet diameter.The experimental results reveal that the whole deformation process of droplet can be divided into a stable phase and a deformation phase,with the increase of shock wave Mach number,the protrusion on the leeward side of droplet and the shearing effect of airflow after the shock wave promote the droplet atomization.When the shock Mach number is similar,reducing the droplet diameter extends the droplet deformation time and results in different deformation features of droplet.The droplet cross-stream diameter and deformation time are dimensionless,the analysis shows that stable phase the droplet crossstream diameter remains constant,deformation phase the cross-stream diameter and dimensionless time satisfy the parabolic pattern of evolution.2.The effect of shock wave strength on the evolution of droplet morphology are explored using numerical simulations.Numerical results show that as the shock Mach number increases,the flattening of the droplet leeward surface occurs earlier,the ripples and folds on the droplet windward surface become more pronounced.Analysis of the development in airflow field near droplet at the initial stage of breakup reveals that the inverse pressure gradient at leeward side of droplet is responsible for the generation of its surface protrusion.The analysis of the parameters during the evolution in droplet morphology reveals that the deformation width of droplet is nonlinearly related to dimensionless time,at the same time,the accuracy of relationship between dimensionless time and cross-stream diameter is verified.3.The morphological evolution of droplet under the effect of different shock Mach numbers are integrated on the time scale,and the integration results show that the scale of droplet windward surface wave is larger than its leeward surface,which is due to the greater shearing effect of droplet on the windward surface,resulting in a stronger aerodynamic effect on droplet windward surface.K-H instability is the main force for liquid mist stripping throughout the deformation and breakup of droplet.The integration of droplet secondary breakup process in time is compared with the jet primary breakup process in analogy,it is found that the integration of droplet cross-stream diameter in time scale exists a similar exponential function with the penetration height of the jet. |
