The Separating Shear Layer Development with the Artificial Disturbances

人工扰动下分离剪切层的发育

基本信息

批准号：
01550159
负责人：
HONAMI Shinji
金额：
$ 1.22万
依托单位：
The Science University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

The separation and reattachment phenomena of turbulent shear layers have been an important subject in the engineering application. A backward-facing step flow has been investigated as a model of separated flows with the reattachment process. The perturbed shear layers can be obtained, when an artificial disturbance is provided upstream of the step edge in the backward facing step flow. For example, a fence installation upstream of the backward-facing step corresponds to the multi-step concept to enhance the turbulent mixing as in a combustor design. The aim of the present project is to understand the reattachment process by using a fence installed upstream of the separation point or by providing the step wall vibrations with a particular frequency and amplitude. Therefore, a local turbulence structure is changed drastically at the step and there might be the possibilities to control the separation and reattachment process.The following fruitful results and conclusions were obtained. The reattachment length has a strong correlation with a fence height or the vibration frequency and the amplitude. The reattachment process can be effectively controlled by changing the disturbance strength. The strong perturbation occures even in the case of a smaller disturbance, in particular, in the turbulence quantities, while the flow with a stronger disturbance involves overwhelming perturbation. The structures in the inner shear layer are strongly affected by the inherent mechanism of the turbulent mixing downstream of the step, although those of the outer shear layer are not altered even in the downstream location.

在工程应用中，湍流剪切层的分离和重现现象一直是重要的主题。已经研究了向后的阶梯流，作为通过重新计算过程的分离流的模型。当在向后朝向式阶梯流中的步进边缘上游提供人造干扰时，可以获得扰动的剪切层。例如，向后的步骤的围栏安装对应于多步概念，以增强燃烧器设计中的湍流混合。本项目的目的是通过使用分离点上游或提供特定频率和振幅的阶梯壁振动来理解重新计算过程。因此，在此步骤中发生了局部湍流结构，并且可能有可能控制分离和重新接触过程的可能性。获得了以下富有成果的结果和结论。重新计时长度与围栏高度或振动频率和振幅具有很强的相关性。可以通过改变干扰强度来有效控制重新处理过程。强烈的扰动甚至在较小的干扰情况下，尤其是在湍流量中也会发生，而干扰更强的流动涉及压倒性的扰动。内部剪切层中的结构受到步骤下游的湍流混合的固有机制的强烈影响，尽管即使在下游位置，外剪切层的结构也不会改变。