单液滴在射流场中的形变及破碎实验研究

Deformation and breakup of individual drops in jet flow fields

在射流场中对自由上升单液滴的形变和破碎过程进行了研究。采用高速摄像技术拍摄记录液滴的初始形状、上升速度、进入射流场后的形变破碎等现象,运用粒子图像测速(PIV)技术研究了射流场的流场情况。通过改变液滴初始粒径大小、入射位置、射流速度等参数考察了在不同射流速度下液滴在流场中的形变破碎过程。结果表明,液滴在进入射流场后会发生3个尺度的形变过程,随后会发生从生成子液滴数为两个至多个不等的二元破碎至多元破碎现象;液滴一次破碎位置随流场剪切力而变化,主体破碎区域为射流场的中间部分;液滴在射流场中生成的子液滴数量会随入射流量、入射位置和母液滴粒径的改变发生变化。

The deformation and breakup process of free rising single drops has been investigated in jet flow fields.The parameters of shape,deformation,rising velocity and acceleration of the drop were obtained by means of a high-speed camera,and flow fields of the jet flow were measured by particle image velocimetry（ PIV） with fluorescent tracer particles. Factors which were varied include the downstream locations of the drop-jet collision,flow characteristics,and initial drop sizes. The complete process of rising,deformation and breakup of the drops as well as the force mechanism were studied. The results show that in order to describe the interaction between turbulent structures and the motion of the fluid- fluid interfaces directly,the deformations of the drop need to be separated into three scales. The influence of the flow shear rate on the broken positions is also discussed. The drop breakup often formed a large number of fragments,and the role played by the flow characteristics in determining the numbers of daughter drops was investigated.