激波冲击下液滴变形破碎的黏性特征

Viscosity characteristics of droplet deformation and breakup under shock wave

为了获得不同黏度的液滴在高速气流中变形破碎的形态特征图像,定量分析黏性对变形破碎过程的影响,使用高速相机直接拍摄法在水平激波管中实验研究了液滴的变形破碎过程,测量了液滴迎风面位移、横向变形宽度、破碎时间等特征参数。所得结果表明:液滴的黏度较低时,液滴尾部形成的尾迹形状为细长的尖锥形,当液滴的黏度较高时,尾迹形状呈现波纹状,随着黏度的逐渐增大,液滴的尾迹更加复杂且紊乱;由于波后气流的作用,液滴迎风面发生变形失稳并演变出'尖钉'结构;黏性对液滴变形破碎过程起阻碍抑制作用;随着液滴黏度的增加,Rayleigh-Taylor(RT)不稳定性发展速率减缓,'尖钉'的数量先增加后减小。

In order to obtain the morphological feature images of different viscous droplets deformed and broken in high-speed airflow,the influence of viscosity in the process of deformation and fracture was quantitatively analyzed,and the high-speed camera direct shooting method was used to study the droplet deformation and crushing process in the horizontal shock tube.The characteristic parameters such as windward surface displacement,lateral deformation width,and crushing time were measured.Results showed that when the viscosity of the droplet was low,the shape of the trail formed by the tail of the droplet was an elongated pointed cone.When the viscosity of the droplet was high,the shape of the trail was corrugated,and the wake of the droplet was more complicated and disordered when the viscosity increased;the windward surface of the droplet was deformed and unstable under the action of the wave,and the'spike'structure was developed;the viscosity of the liquid hindered the deformation and fracture process;the lower viscosity of the drop led to the faster rate of development of Rayleigh-Taylor(RT)instability,and the number of'spikes'increased first and then decreased with the increase of viscosity.