Research On The Deformation Characteristics Of Sub-millimeter Droplets Under Shock Wave

Droplets will deform and break under the action of high-speed airflow.This is a very common phenomenon in fluid mechanics,and it is also widely used in engineering applications.For example,when an airplane is flying at high speed,it will produce compression waves,which will interact with liquids such as raindrops in the atmosphere.Particles collide.This phenomenon will have an erosive effect on the surface coating of the aircraft.Research in this area can effectively improve the erosion effect of raindrops on the aircraft;due to the increase in the speed of hypersonic aircraft,a complex wave system will be generated in the engine combustion chamber.,Research on droplets helps to improve the performance of the engine.Therefore,it is necessary to study the deformation characteristics of sub-millimeter droplets.This paper is based on the research of the deformation and breaking process of sub-millimeter droplets in a horizontal shock tube,based on a pressure-based solver,the deformation characteristics of sub-millimeter droplets under shock wave are numerically evaluated through the VOF multiphase flow model and the k-εturbulence model.The deformation and breaking process of sub-millimeter droplets are analyzed by two-dimensional and three-dimensional numerical simulation methods.The Mach number range of sub-millimeter droplets by shock waves is 1.07-1.36 Ma.Four typical crushing modes,such as bag crushing,bag core crushing,shear crushing and explosive crushing,are compared and analyzed by experiments and numerical simulations.The initial diameter and Weber diameter of droplets are analyzed by changing different initial conditions.The influence of Mach number and Mach number on the deformation and crushing process of droplets,the critical Weber number range for the change from bag-like crushing mode to bag-core crushing mode is obtained.The time-space relationship is studied and analyzed on the deformation movement process of the droplet.By dimensionless parameters such as the displacement of the sub-millimeter droplet’s windward surface,the deformation and breaking time of the sub-millimeter droplet,and the lateral deformation width during the development of the droplet,the paper draws the following conclusions:(1)In the stable deformation stage,The lateral deformation width of the sub-millimeter droplet is positively correlated with time;(2)Under the condition of low Weber number,when the breaking mode and the aerodynamic force of the acting droplet remain unchanged,the larger the initial diameter of the droplet,the maximum dimensionless lateral deformation The smaller the width.Under the condition of high Weber number and the same aerodynamic force in the same crushing mode,the dimensionless maximum transverse deformation width of sub-millimeter droplets increases with the increase in diameter,and the transverse expansion rate of the droplets increases with the increase of Weber number.Large;(3)After the maximum deformation is completed in the sub-millimeter droplet bag-like crushing mode,as the bag-like structure is broken,the dimensionless lateral deformation width of the droplet tends to increase.However,when the sub-millimeter reaches the maximum deformation width in the shear and explosive crushing modes,the dimensionless lateral deformation width of the droplets tends to decrease;(4)The sub-millimeter droplet bag crushing mode is transformed into the bag core crushing mode.The critical Weber number is in the range of 25-28;(5)Under different initial conditions,the dimensionless displacement of the sub-millimeter droplet on the windward surface meets the shape of the quadratic parabola when the sub-millimeter droplet is subjected to aerodynamic force.The acceleration of the displacement of the windward surface is constant.(6)Under the same diameter,the dimensionless value of the deformation completion time of sub-millimeter droplet bag crushing,bag core crushing,shearing crushing and explosive crushing gradually decreases,and the transverse expansion rate of droplets perpendicular to the airflow direction increases with the Weber number the increase of the increase.The acceleration of the sub-millimeter droplet moving downstream along the airflow direction increases with the increase of the Weber number.(7)The initial diameter of the droplet plays a decisive role in the velocity of the droplet moving along the direction of the airflow.Under the same breaking mode,when the sub-millimeter droplet is subjected to aerodynamic force,the larger the initial diameter of the sub-millimeter droplet,the larger the droplet along the airflow,the smaller the acceleration in the direction.(8)When the initial diameter of the sub-millimeter droplet does not change much,the larger the Weber number,the acceleration of the displacement of the sub-millimeter droplet on the windward surface gradually increases.