Active Control of Turbulent Separated Flows

湍流分离流的主动控制

基本信息

批准号：
03452120
负责人：
KIYA Masaru
金额：
$ 4.22万
依托单位：
(Faculty of Engineering) Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03452120/
关键词：
Turbulence Complex Turbulent Flow Separated Flow Flow Control Periodic Disturbance Active Control Separated Flow Region Turbulence Structure はく離泡はく離再付着流れ渦力学再付着長さ

项目摘要

(1) The leading-edge separation bubble of a blunt circular cylinder with the square-cut leading edge (the blunt circular cylinder) was forced by single-frequency sinusoidal disturbances introduced along the separation edge; the frequency and level of the forcing were systematically changed to obtain the response of the vortex structure in the separated shear layer to the forcing. The reattachment length of the separation bubble attained a minimum at a particular forcing frequency f_<min>. This frequency, if normalized by the free-stream velocity and the radius of the cylinder, remained constant at different forcing levels. The minimum reattachment length decreased with increasing forcing frequency. (2) The frequency f_<min> is 2^n (n:integer) times the frequency of shedding of large-scale vortices from the reattachment region of the separation bubble. This result was obtained by assuming that the separation bubble is a self-excited system and that the minimum reattachment length is rea … More lized when the large-scale vortices are shed from the reattachment region immediately after its formation by the vortex amalgamation. (3) The bimodal forcing was studied by introducing sinusoidal disturbances with two frequencies f_1 and f_2, the strength of each component of the disturbances being chosen to be the same. The frequency f_l was equal to the said frequency f_<min> while the frequency of the second component f_2 was higher harmonics and subharmonics of the first component. The phase between the two components was changed from 0 to 2pi. The most significant dependence of the reattachment length on the phase difference PHI between the two components was observed for f_2=2f_1, i.e. the first higher harmonics. (4) The decrease in the reattachment length by the forcing is produced by the formation of larger vortices at shorter positions downstream of the separation edge. For sufficiently high level of forcing, the natural amalgamation process of the shear layer is bypassed to produce the large vortices. This is the mechanism of the decrease of the reattachment length. Less

（1）平圆形圆柱体的前缘分离气泡，其正方形前缘（钝圆圆柱体）被沿分离边缘引入的单频弦曲线灾害强迫；系统更改强迫的频率和水平，以获得分离的剪切层中涡流结构对强迫的响应。分离气泡的保留长度在特定的强迫频率f_ min>下连接了最小值。如果通过自由流速度和圆柱体的半径对该频率进行标准化，则在不同的强迫水平下保持恒定。随着强迫频率的增加，最小保留长度降低。（2）频率f_ <min>为2^n（n：整数）乘以分离气泡的保留区域中大规模涡流脱落的频率。通过假设分离气泡是一个自激发系统，并且最小重新触及的长度是re的，从而获得了这一结果……当大规模涡流通过涡流融合形成后立即从保留区域脱离时，会更加含糊。（3）通过引入两个频率f_1和f_2的正弦灾害来研究双峰强迫，这是灾害的每个组成部分的强度。频率f_l等于上述频率f_ <min>，而第二个组件的频率f_2的频率为较高的谐波和第一个组件的亚harmonics。两个组件之间的相位从0更改为2pi。对于F_2 = 2F_1，即第一个较高的谐波，观察到保留长度对两个组分之间的相位差PHI的最显着依赖性。（4）通过强迫的保留长度的减小是通过在分离边缘下游较短位置的较短位置形成较大的涡流产生的。对于足够高的强迫，剪切层的自然合并过程被绕开以产生大涡流。这是保留长度减小的机制。较少的