Research on the Vortex Structure in Rotating Cavity Flow by means of Simultaneous

本研究旨在阐明均匀轴向旋转圆柱体周围形成的空腔内流动的涡结构。长宽比，即空腔宽度与深度的比值。从1到4不等。实验在水洞中进行，采用粒子成像测速仪（PIV）和超声测速仪（UVP）进行测量。本文的研究进展及取得的主要成果如下：根据轴对称势流原理，建立了鼻部为流线型的圆柱模型。圆柱体的后端由悬臂支撑，前部由细钢丝支撑。开发了基于互相关法的PIV测量软件，并对其进行了改进，使其能够准确测量腔内变化幅度较大的速度。进一步开发了用于同时测量的软件，并与PIV和UVP进行了更多的测试，并对在水中播种的示踪颗粒进行了咨询。因此，我们决定同时使用荧光染料用于PIV和电解水产生的氢气泡用于dvp。在上述初步研究的基础上，对展弦比为1和4的腔内流场进行了实验。首先，不旋转圆柱的流动显示显示，空腔流动呈现出二维空腔流动中由与空腔深度相当尺度的主涡和部分次涡组成的旋涡结构，并且在空腔上游边缘分离的剪切层振荡，再附着点位置呈准周期性变化。通过PIV测量得到了平均速度矢量图和平均涡量等值线图。它们定量地展示了主涡和次涡的大小和结构。从DVP测量中检验了分离剪切层的时空行为。揭示了切变层的时空摇摆现象，得到了切变层振荡的平均频率和波动速度的时空相关性。为了阐明轴对称空腔内的三维涡旋结构，我们将进行更详细的测量和数据分析，并将研究剪切层的卷起现象、剪切层在空腔下游边缘的剪切、波动涡量分布等。少

This research aims to clarify the vortex structure of the flow in a cavity formed peripherally on a cylinder rotating in a uniform axial stream. The aspect ratio, i.e., the ratio of the width of the cavity to the depth. was varied from 1 to 4. Experiments were carried out in a water tunnel, and measurements were made by using a PIV (Particle Imaging Velocimetry) and a UVP (Ultrasonic Velocity Profile Monitor). A progress of this research and main results obtained are as followings.1. The cylinder model was made, whose nose part was of streamline shape based on the axisymmetric potential flow. The cylinder was supported as a cantilever on its rear end and by fine wires on its front part.2. The soft ware for PIV measurements to analyze the images on the basis of cross-correlation method was developed, and it was refined as to measure accurately the velocity in the cavity which varied over wide range in its magnitude. Further the development of the soft ware for the simultaneous measureme … More nt with the PIV and UVP was undertaken, and the consultation was made for the tracer particles seeded in the water for this measurement. As a result we fixed to use simultaneously the fluorescent dye for the PIV and the hydrogen bubbles generated by the electrolysis of the water for the DVP.3. Following the above preliminary research, the experiment was made for the flow field in the cavity of its aspect ratio 1 and 4. First, the flow visualization with no rotation of the cylinder revealed that the cavity flow presented the vortex structure composed of a main vortex of the scale comparable to the cavity depth and of some secondary vortices as in two-dimensional cavity flow, and also that the shear layer separated at the upstream edge of the cavity oscillated and the position of reattachment point varied quasi-periodically.4. The vector map of the mean velocity and the contour map of the mean vorticity were obtained from the PIV measurement. They exhibited the magnitude and the configuration of the main vortex and the secondary vortices quantitatively. The spatio-temporal behavior of the separated shear layer was examined from the DVP measurement. The phenomenon of the spatio-temporal swaying of the shear layer was revealed, and the mean frequency of the oscillation and the space-time correlation of the fluctuating velocity in the shear layer were obtained.5. We proceed with more detailed measurements and data analyses, and will investigate the roll-up phenomenon of the shear layer, the clipping of the layer on the downstream edge of the cavity, the fluctuating vorticity distribution, and so on, in order to clarify the three-dimensional vortex structure in the axi-symmetric cavity. Less