STUDY ON TURBULENCE STRUCTURE AND ACTIVE CONTROL OF A THREE-DIMENSIONAL SEPARATED FLOW

三维分离流湍流结构及主动控制研究

基本信息

批准号：
05452148
负责人：
KIYA Masaru
金额：
$ 3.97万
依托单位：
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：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452148/
关键词：
Turbulent shear flow Flow separation Flow reattachment Flow control Active control Sinusoidal disturbance Separation bubble Separated shear layr はく離流れ乱流はく離泡周期的攪乱乱流鈍頭物体

项目摘要

A turbulent separation bubble formed by the boundary-layr separation from the leading edge of a blunt circular cylinder of semi-infinite length was forced by a single-frequency and two-frequency sinusoidal disturbances introduced uniformly along the separation edge. The disturbance was generated by a woofer inside the cylinder and introduced into the separated shear layr through a thin slot. Main results for the single-frequency forcing may be summarized as follows :(1) The reattachment length attains a definite minimum at a particular forcing frequency if the r.m.s.forcing amplitude is less than 10% of the main-flow velocity. A flow model was proposed to successfully interpret this frequency (referred to as the most-effective frequency F) and the minimum reattachment length, which is a logarithmic function of the forcing amplitude.(2) The separation bubble can be eliminated in a range of the forcing frequency for the forcing amplitudes greater than 14% of the main-flow velocity. This … More range of the forcing frequency tends to increase with increasing forcing amplitude. This result is useful in active control of flow separation on aerofoils and cascades of turbomachinery.(3) The separation bubble is a self-excited flow maintained by a feedback loop : The disturbance produced by a large-scale vortex impinging on the surface in the reattachment region of the separation bubble propagates upstream as a pressure wave to be accepted at the sharp separation edge. The disturbance enhances the rolling-up of the separated shear layr.(4) The structure of large-scale vortices in the separation bubble forced at the most effective frequency was obtained in terms of cross correlations of velocity fluctuations at two points separated in the circumferential direction and flow visualization by smoke wires and tuft probes.Main results for the two-frequency forcing may be summarized as follows :(5) The combination of the most effective frequency F and its higher harmonic 2F yields a minimum reattachment length at a phase difference of 0 and a maximum reattachment at another phase difference of pi. This result was successfully interpreted in terms of the subharmonic instability of the classical plane mixing layr.(6) The two-frequency forcing yields approximately the same reduction of the reattachment length as the single-frequency forcing if the forcing amplitude is of the order of 10% of the main-flow velocity.A discrete-vortex numerical simulation of the forced separation bubble reproduced the relation between the reattachment length and the forcing frequency, and more importantly useful pieces of information on a feedback control of the separation bubble. Less

由单频沿分离边缘统一引入的，由单频和两频正弦灾害迫使由边界长度的钝圆圆柱与半临时长度的钝圆圆柱的前缘形成的湍流分离气泡。这场灾难是由气缸内部的低音扬声器产生的，并通过薄插槽引入了分离的剪切层。单频强迫的主要结果可以总结如下：（1）如果R.M.S.Forping放大器小于主流速的10％，则保留长度在特定强迫频率下达到定义的最小值。提出了一个流量模型，以成功解释该频率（称为最有效的频率F）和最小保留长度，这是强迫放大器的对数函数，大于主流速的14％。这种……随着强迫放大器的增加，更多的强迫频率倾向于增加。该结果有助于积极控制涡轮机构和涡轮机械级联反应的流动分离。（3）分离气泡是一种由反馈循环维持的自激发的流动：由大规模涡流造成的灾难会撞击大型涡流，撞击了在分离气泡的保留区域中的表面上，造成了压力波的保留区域，以使上流波动地散发出锋利的分离。灾难增强了分离的剪切衬里的滚动。（4）在两个点相关的速度波动的跨相关性方面，在两个点分离的速度波动的跨相关性方面，在绕线和脉动可视化的频率下，有效的频率是，均为两种频率的频率（均为效率），从而有效地划分了，这是有效的，从而有效地划分了两种频率： F及其较高的谐波2F在相差0的相位差和最大保留率下在PI的另一个相位差时产生最小保留长度。该结果通过经典平面混合层的亚谐音不稳定而成功解释。（6）两种频率强迫的产生的保留长度的减小与单频强迫的缩短大致相同，如果强迫放大器是主流速度的10％的依次分离的延长阶段，则依次分离的延长范围。强迫频率，更重要的是有关分离气泡反馈控制的有用信息。较少的