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

本研究旨在探讨均匀轴向来流中旋转圆柱周向空腔内流动的涡结构。纵横比，即，腔的宽度与深度的比率。从1到4不等。实验在水洞中进行，并通过使用PIV（粒子成像测速仪）和UVP（超声速度剖面监测仪）进行测量。本课题的研究进展和主要结果如下：1.基于轴对称势流建立了头部为流线型的圆柱体模型。圆柱体的后端是悬臂，前端是细金属丝。开发了基于互相关法的PIV测量软件，并对软件进行了改进，使其能够准确测量大范围变化的空腔内的速度。同时测量软件的进一步开发 关于我们 进行了与PIV和UVP的对比试验，并对水中的示踪粒子进行了咨询。因此，我们决定同时使用荧光染料进行PIV和通过电解水产生的氢气泡进行DVP。3.在上述初步研究的基础上，进行了深宽比为1和4的凹腔流场的实验研究。首先，无旋转圆柱的流动显示了空腔流动呈现出与二维空腔流动相似的由尺度与空腔深度相当的主涡和若干次涡组成的涡结构，并且在空腔上游边缘分离的剪切层呈准周期性振荡，再附着点的位置也呈准周期性变化。通过PIV测量得到了平均速度矢量图和平均涡量等值线图。它们定量地显示了主涡和次涡的大小和结构。分离剪切层的时空行为进行了检查，从DVP测量。揭示了剪切层的时空摆动现象，得到了剪切层中脉动速度的平均振荡频率和时空相关性.我们将继续进行更详细的测量和数据分析，并将调查的卷起现象的剪切层，剪切层的剪切下游边缘的空腔，脉动涡量分布，等等，以澄清三维涡结构的轴对称空腔。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