真空羽流中相变过程DSMC仿真方法研究  

RESEARCH ON DSMC NUMERICAL METHOD OF PHASE TRANSITION IN VACUUM PLUME

作　　者：李中华[1,2] 李志辉[3] 吴俊林[1,2] Li Zhonghua;Li Zhihui;Wu Junlin(Hypervelocity Aerodynamics Institute,China Aerodynamics Research and Development Center,Mianyang 621000,Sichuan,China;National Key Laboratory of Aerospace Physics in Fluids,China Aerodynamics Research and Development Center,Mianyang 621000,Sichuan,China;National Laboratory of Computational Fluid Dynamics,Beijing 100191,China)

机构地区：[1]中国空气动力研究与发展中心超高速空气动力研究所,四川绵阳621000 [2]中国空气动力研究与发展中心飞行器流体物理全国重点实验室,四川绵阳621000 [3]国家计算流体力学实验室,北京100191

出　　处：《力学学报》2024年第5期1356-1365,共10页Chinese Journal of Theoretical and Applied Mechanics

摘　　要：真空燃气羽流快速膨胀过程中,其中的H_(2)O和CO_(2)等组元容易发生凝结相变现象.为了研究真空羽流中水蒸气的相变产物冰晶对羽流红外信号、侵蚀等污染效应的影响,开展羽流中相变过程的数值模拟方法研究.基于稀薄两相羽流双向耦合DSMC方法,采用经典成核理论和液滴生长理论,建立了真空羽流的相变过程的数值仿真方法.对水蒸气在拉法尔喷管中自凝结试验的仿真.通过与试验结果的对比,对经典成核理论进行了修正,对成核率给出了10^(3)的修正因子,可以得到与试验符合的仿真结果,表明对成核理论修正后,可以应用到稀薄流动的数值模拟中.对某发动机真空羽流相变流场的仿真,在核心区得到与CFD相近的结果.仿真结果表明,在羽流流场中,由于相变,存在较多的冰晶颗粒,在计算条件下,羽流核心区冰晶数密度最大达到10^(15) m^(-3)的量级,冰晶直径在约10^(-8) m的量级.在真空环境下,随着羽流向倒流区无限制膨胀,倒流区流场内也会出现一定数量的冰晶颗粒,数密度从10^(7)~10^(10)m^(-3)的量级,直径在5.0×10^(-10)m的量级.颗粒在空间的数密度、尺寸等分布与气相分布存在差异,需要开展相关污染效应的影响研究.During the rapidly expansion of vacuum gas plume,the condensation phase transition is easy to occur for species such as H_(2)O and CO_(2) in gas phase.Numerical simulation method of phase transition process in vacuum plume is studied to research the contamination effects of infrared and erosion caused by ice crystal particles produced from vapor by phase transiting in plume.Based on two way coupled direct simulate Monte Carlo(DSMC)method which simulates the momentum and energy exchange between phases used in rarefied two phase plume,the numerical method of phase transition in vacuum plume is modeled by using classical nucleation theory and droplet growth theory.The experimental cases of vapor spontaneous condensation in a Laval nozzle are simulated.By comparing the results between numerical simulation and experiment,the classical nucleation theory is modified by setting a correction factor of 10^(3) for the nucleation rate,then the simulation results which are good agreement with those of experiment can be obtained.This means that the modified classical nucleation theory can be used in numerical simulation of rarefied flow.The vacuum plume with phase transition of a thruster is simulated,and similar result with CFD in kernel flow is acquired.It is show that there are a number of ice crystal particles because of phase transition in plume field.In plume kernel flow,the maximum of ice crystal number density reaches the order of 10^(15) m^(-3),and the diameter is on the order of about 10^(-8) m in the simulated case.There are a certain amount of ice crystal in back flow because of the plume unlimited expansion in vacuum,with the number density on the order of 10^(7) to 10^(10) m^(-3),and the diameter on the order of 5.0×10^(-10) m.There are some distinctly difference between particle and gas phase about number density and size spatial distribution,and it is needed to study the related contamination effects of plume.

关 键 词：真空羽流 相变 成核 直接模拟蒙特卡罗 数值仿真 

分 类 号：O356[理学—流体力学]