Numerical Simulation Of Gas-Liquid Two-phase Flows In Supersonic Flows Based On The Interface Capturing Method Under Adaptive Mesh Refinement Framework

Research of liquid jet in a supersonic crossflow is an important part in the development of scramjet engine.Primary and secondary breakup are two main process in the breakup of liquid jet in a supersonic crossflow.The primary breakup happens in the near-filed around the injector nozzle.And the secondary breakup can be considered as droplet breakup.The interaction between liquid and supersonic flows was studied based on an efficient and robust simulation system which was developed in this thesis for compressible two-phase flow.The two-phase flow was modeled by interface capturing method.And the comparison was carried out among (?)-model,fraction model and five-equation model.HLL-family and AUSM-family methods were introduced for the stable solution of the two-phase governing equations.To avoid the numerical oscillation,primitive variables or characteristic variables which come from the projection of the primitive variables onto the characteristic fields are suggested to be reconstructed for reaching higher order accuracy.In addition,a MOON-type positivity preserving method was adopted to guarantee the robustness of the simulation system.Also,anti-diffusion method and adaptive mesh refinement were used to overcome the drawback of the diffused interface method.Breakup single droplet and binary droplets collision in a supersonic flow was simulated by the simulation system developed in this thesis.surface instability,shear stripping and final breakup are three main process of single droplet breakup.During the process of surface instability,the unstable waves were centered in the transonic area.In a Mach 1.8 supersonic flow,a piercing structure was formed in the middle of the droplet.While in a Mach 2.3 supersonic flow,the middle part of the droplet breakup directly without forming a piercing structure.The binary droplets collision was summarized into three stages: deformation before collision,collision and final breakup.The movement and breakup time of droplet was obtained with mass-averaged statistics.Near-filed of liquid jet breakup in a supersonic crossflow was simulated by the simulation system developed in this thesis.The primary breakup of liquid jet in a supersonic crossflow contains column breakup and surface breakup.Column breakup coms from the instabilities traveling along the liquid jet.And liquid is striped from the liquid jet because of the surface breakup which comes from the small size surficial instabilities centering in the transonic area.Influences of Mach number and liquid-gas momentum ratio were also studied.Through simulations of the liquid injected periodically,the pulsing and sinusoidally periodic injections were studied in this thesis.The influence of frequency and duty cycle ratio were studied in the pulsing injection.And the influence of frequency and sinusoidal amplitude were studied in the sinusoidally periodic injection.Drawbacks and advantages were also discussed by comparing pulsing and sinusoidally periodic injections.