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Development of a driving method for high-intensity turbulence through independent controllability of multi-fan wind tunnels

多风扇风洞独立可控高强度湍流驱动方法开发

基本信息

批准号：
17560430
负责人：
OZONO Shigehira
金额：
$ 1.95万
依托单位：
University of Miyazaki
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

The purpose of the present research is to generate both high-intensity and large-scale turbulence by using a multi-fan wind tunnel. Since air flow is driven by an array of small 99 fans, various flows can be generated., However, the question as to how to generate both high-intensity and large-scale turbulence is still open. As basic driving methods, we have (1) uniformly active mode and (2) quasi-grid mode, but the resulting turbulence is far from the real atmospheric turbulence.By combining driving mode (1) and (2), we have tried an active-grid method. With a few sinusoidal fluctuations fed, we have measured turbulent fields with attention focused on whether turbulence intensity can be amplified. That means we try to generate high-Reynolds number turbulence to amplify turbulent energy by providing external fluctuations. Except a sharp peak associated with input fluctuations, there is little change in the resulting spectra.After an update of the wind tunnel used, suction becomes available by rotating fans in the reverse direction. It was found that the effect of suction is to maximize mixing immediately downstream of blowing, and random differences in phase of each fan allow mixing to enhance. However, we have not removed pulsating component originated from the external fluctuations yet.Furthermore, we have attempted fractal arrangement of the fans. The resulting turbulence satisfied isotropy to some degree, but non-uniformity survives over some streamwise distance.

本研究的目的是通过使用多风扇风洞产生高强度和大规模的湍流。由于气流是由一系列99个小型风扇驱动的，因此可以产生各种流动。然而，如何产生高强度和大规模的湍流仍然是一个悬而未决的问题。作为基本驱动方法，我们有（1）均匀主动模式和（2）准网格模式，但产生的湍流与真实的大气湍流相差甚远。通过结合驱动模式（1）和（2），我们尝试了主动网格方法。通过输入一些正弦波动，我们测量了湍流场，重点关注湍流强度是否可以放大。这意味着我们试图通过提供外部波动来产生高雷诺数湍流，以放大湍流能量。除了与输入波动相关的尖峰外，所得光谱几乎没有变化。更新所用的风洞后，通过反向旋转风扇即可获得吸力。研究发现，吸力的作用是在吹风下游立即实现最大程度的混合，并且每个风扇相位的随机差异可以增强混合。然而，我们还没有去除源自外部波动的脉动分量。此外，我们还尝试了风扇的分形排列。由此产生的湍流在某种程度上满足各向同性，但在一定的流向距离上仍然存在不均匀性。