剪切流场中液滴形变的三维力学模型初探

Investigation on the three-dimensional mechanical model of deformation of a single droplet in shear flow

分析了油水乳化液中分散相液滴的受力及形变,从理论上提出了剪切流场中液滴形变的三维力学模型。通过实验观测了液滴在由两个同心圆筒形成的旋转剪切流场中的变形情况,并对建立的三维力学模型进行了验证。测量结果表明:实验观测值和理论值有较好的一致性。未加乳化剂时,在z方向上,随着液滴拉伸率的增加,液滴的变形收缩系数也随之增加;与未加乳化剂时相比,加入乳化剂时液滴的变形收缩系数偏离理论值更大;对于有表面活性剂的自由液滴来说,液滴破裂所需要的临界剪切率比没有表面活性剂时要低。

Through the analysis of suffering force and deformation of a single droplet in the discrete phase of oil-water in shere flow, a theoretical mechanical model of deformation of a single droplet was propounded. The deformation of a single droplet was observed in shear flow formed by two coaxial cylinders. The three-dimensional mechanical model of deformation of a single droplet was verified through the experiment. The measurement shows that there is good consistency between experimental results and theoretical results. In the direction of z coordinate, the deformation shrinkage coefficient of a single droplet without emulsifier increases along with the increasing of stretching rate. The deformation shrinkage coefficient of a single droplet with emulsifier deviates more from the theoretical results than that without emulsifier. The critical shear rate for the breakup of a single droplet with surfactant is lower than that without surfactant.