STUDY OF BIFURCATION OF ROTATING FLOW IN A CLOSED SPACE AND ITS EFFECTS ON THE PARTICLE MOTION IN THE FLOW

旋转流场不仅对纯流体力学具有重要意义，而且对工程问题和环境问题也具有重要意义。作为一种旋转流动范式，多年来人们从不同的角度对封闭容器内的流场进行了研究，但仍有许多问题有待澄清。本文研究了两种旋转流，一种是本杰明流，即有限长的泰勒涡流；另一种是旋转圆盘流。对于本杰明流，我们用数值和实验相结合的方法进行了研究。具体地，对减速缸情况下流型的非线性发展进行了详细的计算，得到了详细的分叉过程。并与实验结果进行了比较，计算结果与实验结果吻合较好。但在某些情况下，实验中的分叉过程更为复杂。一个重要的争议点是如何根据计算结果客观地确定流型。我们利用人工智能技术构建了一个程序，可以解释复杂的泰勒涡的形成过程，从而可以在没有主观知识的情况下对各种流型进行分类。作为分析旋转流动中颗粒运动的第一步，采用了用Java编写的Runge Kutta格式来追踪流体颗粒的轨道，并构建了方便的图形用户界面系统。建立了一套实验装置，对封闭腔内旋转圆盘诱导的流动进行了可视化研究。采用铝粉法进行可视化，用摄像机拍摄流场，并用图形软件进行分析。根据旋转圆盘直径和圆周速度所定义的雷诺数递增，对流型进行了分类。

Rotating flow field is important for pure fluid mechanics but also for engineering problems and environmental problems. As a rotating flow paradigm, flow field in a closed vessel are investigated many years from various points of view but still many questions are remained to be clarified. In this research, two types of rotating flow are studied, one is Benjamin flow, that is Taylor vortex flow in finite length and the another is rotating disc flow. For Benjamin flow, we studied using numerical and experimental methods. Specifically, Nonlinear development of flow patterns in the case of decelerating cylinder is carefully calculated and details of bifurcation process is obtained. The comparison is made between an experiment, and the calculated results and excellent agreement is obtained. But in some cases bifurcation process is more complicated in the experiment. An important controversial point is to determine the flow pattern objectively from the computed results. We constructed a program which can clarify complicated formation process of Taylor vortex using artificial intelligence technique so we can classify various flow pattern without subjective knowledge. As the first step to analyze the motion of particles in rotating flow, an orbit of fluid particle is pursued using Runge Kutta scheme of which is written in JAVA and convenient GUI system is constructed. An experimental facility is made for flow visualization for the flow induced by a rotating disc in an enclosure. Aluminum powder method is used for visualization and flow field photographed by video camera recorder and analyzed by a graphic software. Regimes of flow field are classified according to increasing Reynolds number defined by the diameter of the rotating disc and peripheral velocity of it.