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有重要意义，而且对工程问题和环境问题也有重要意义。密闭容器内的流场作为一种旋转流动范式，多年来人们从各个角度对其进行了研究，但仍有许多问题有待澄清。本研究研究了两种类型的旋转流动，一种是本杰明流动，即有限长度的泰勒涡流动，另一种是旋转圆盘流动。对本雅明流进行了数值和实验研究。具体地说，对减速缸情况下流型的非线性发展进行了细致的计算，得到了分岔过程的细节。并与实验结果进行了比较，计算结果与实验结果非常吻合。但在某些情况下，实验中的分岔过程更为复杂。从计算结果中客观地确定流型是一个重要的争议点。我们利用人工智能技术构建了一个程序来澄清泰勒涡复杂的形成过程，使我们可以在没有主观知识的情况下对各种流型进行分类。作为分析旋转流中粒子运动的第一步，采用JAVA编写Runge Kutta格式求解流体粒子的运动轨迹，并构建了方便的GUI系统。制作了一种用于显示封闭体中由旋转圆盘引起的流动的实验装置。采用铝粉法对流场进行可视化处理，用摄像机拍摄流场，并用图形化软件进行分析。根据旋转圆盘直径和周围速度所定义的雷诺数的增加来划分流场的状态。

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.