低密度风洞瑞利散射测速实验中纳米粒子跟随性数值分析  

NUMERICAL ANALYZITION OF NANO-PARTICLE FOLLOWING FEATURES FOR RAYLEIGH SCATTERING VELOCITY MEASUREMENT TEST IN LOW DENSITY WIND TUNNEL

作　　者：李中华[1] 李志辉[1] 陈爱国[1] 吴俊林[1] Li Zhonghua;Li Zhihui;Chen Aiguo;Wu Junlin(Hypervelocity Aerodynamics Institute, CARDC, Mianyang 621000, Sichuan, China)

机构地区：[1]中国空气动力研究与发展中心超高速所,四川绵阳621000

出　　处：《力学学报》2017年第6期1243-1251,共9页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家重点基础研究发展计划(2014CB744100);国家自然科学基金(11325212;91016027)资助项目

摘　　要：在低密度风洞试验流场中,加入少量纳米粒子,可以增强瑞利散射测速试验的散射光强度.纳米粒子能否适应流场气流速度变化是测量结果准确性的关键.为了研究瑞利散射测速实验中测量到的纳米粒子的速度能否反映流场当地气流速度,采用基于直接模拟蒙特卡罗方法的稀薄两相流双向耦合算法,对低密度风洞流场中纳米粒子在大梯度流场中的跟随性进行了数值研究.仿真了10 nm,50 nm和100 nm TiO_2三种尺寸的纳米粒子分别在M6和M12低密度风洞返回舱高超声速绕流流场中的运动特性.仿真结果显示,不同尺寸的纳米粒子在不同的流场稀薄度条件下的跟随性不同,纳米粒子尺寸越小,跟随性越好.在稀薄度较低的M6流场中,10 nm粒子跟随性很好,与瑞利散射测量结果比较接近,粒径50 nm以上的粒子跟随性较差,而在稀薄度较高的M12流场中,10 nm粒子的跟随性也变差,表明通过瑞利散射测量到的纳米粒子速度和流场中气体速度有一定差距,不能准确反映流场当地速度.The scattering light intensity can be enhanced in Rayleigh scattering measurement velocity test by adding a small quantity of nano-particles into low density wind tunnel flow field.It is a key factor for the accuracy of measurement result whether nano-particles can adapt the variation of the flow velocity.To investigate the measurement velocity of nano-particle by Rayleigh scattering test whether or not can represent the local flow field velocity,a two-way coupling DSMC method used in rarefied two phase flow is applied to simulate following features of nano-particle in low density flow filed with large grads.TiO2particles with10nm,50nm,100nm diameter in low density hypersonic flows around a spaceship model in M6and M12cases are carried out respectively.It is shown that the following features of variety size nano-particles in different rarefication flow are distinguishing,and the following feature of smaller size nanoparticle is good in complex hypersonic flow.In simulation results,10nm nano-particle's following feature in lower rarefication of M6is better,and good agreement with Rayleigh scattering measurement result.Following features of particle with diameter larger than50nm are bad,and in higher rarefication of M12,even10nm nano-particle's following feature become worse.This means that velocity of particle measured by Rayleigh scattering can not reflect velocity of flow field.

关 键 词：瑞利散射 低密度风洞 纳米粒子 跟随性 直接模拟蒙特卡罗方法 

分 类 号：O356[理学—流体力学]