圆筒容器内起旋和降旋过程中分层液体混合现象

针对旋转圆筒容器内的两种分层流体,应用平面激光诱导荧光与高速摄影技术对互溶与不互溶液体进行了实验研究.结果表明,上下层液体密度梯度与黏度梯度方向是产生界面不稳定的关键因素.当二者的梯度方向相同时,起旋过程不会发生剧烈混合,降旋过程中轻流体会冲击重流体;当二者的梯度方向相反时,起旋过程中形成抽吸效应,其后期发生界面破碎,降旋过程中重流体冲击轻流体.在旋转的3个过程中,降旋过程对混合的作用最大,无论梯度方向是否相同,都会发生液体间的界面不稳定.

THE MIXING PROCESS OF STRATIFIED LIQUID IN A ROTATING CYLINDER

This paper studies the flow process of two stratified fluids in a cylinder, using the Planar Laser Induced Fluorescence and the High Speed Camera techniques, covering both miscible and immiscible stratified liquids. It is shown that the directions of the liquid density gradient and the viscosity gradient are the key factors for the interface instability between liquids. When the directions of the two gradients are the same, the violent mixing would not occur during the spin-up process, and the light fluid will impact the heavy fluid during the spin-down process. When the directions of the two gradients are not the same, the pumping action occurs during the spin-up process, the interface breaks up in the later period of the spin-up, and the heavy fluid will impact the light fluid during the spin-down process. Among the three stages of spinning—the spin-up, the rigid body rotation and the spin-down, the spin-down has a big effect on the mixing process, which means that no matter whether the directions of the two gradients are the same, the interface instability between liquids will occur.