Turbulent swirling flows viewed from the notion of helicity

从螺旋度的概念看湍流旋流

基本信息

批准号：
17540349
负责人：
YOKOI Nobumitsu
金额：
$ 1.86万
依托单位：
University of Tokyo
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 2006
项目状态：
已结题

项目摘要

A variational analysis based on the notion of the helicity (correlation between the velocity and the vorticity) was performed. It was shown that the mean-velocity profiles that minimize the enstrophy of the mean flow under the constraint of the constant helicity is realized, whose profiles are in good agreement with the counterpart observed in a turbulent swirling flow. In addition to the helicity constraint, we took the angular-momentum conservation into consideration. This treatment made it possible to reproduce the mean-velocity profiles in an axially rotating turbulent pipe flow in a manner similar to the case in a turbulent swirling flow, whose behaviors appeared to be totally different from each other.The turbulent helicity has been expected to be one of the important turbulent quantities in describing the large-scale structures in tubulent flows. It is, however, true that information on turbulent helicity has been lacking in the study of turbulence. This made it difficult to appropriately simulate turbulent flows with a turbulence model adopting the helicity as a basic statistical quantity. In this research, data of the representative experiment of turbulent swirling flows were re-examined from the viewpoint of the turbulent helicity. The analysis revealed what mechanism is dominant in producing the turbulent helicity.Another improvement is attained in relation to the eccentricity of the turbulent swirling flow in the center region. The highly asymmetric mean-velocity profiles in the center region observed in the experiments were calibrated with the aid of physical arguments such as the symmetry and conservation properties of the swirling flow. It is expected that this calibrated profiles provide a firm basis for the numerical simulation of the turbulent swirling flow.

进行了基于螺旋性概念（速度与涡度之间的相关性）的差异分析。结果表明，在实现恒定螺旋度的约束下，平均流的胚胎的胚胎的胚胎的平均值曲线已实现，其曲线与在湍流旋转流中观察到的对应物非常吻合。除了螺旋性约束外，我们还考虑了角度摩肌保护。这种治疗方法使得以类似于湍流的旋转流动中的情况相似的方式重现均值旋转的湍流流动的平均值曲线，其行为似乎完全不同。但是，确实缺乏有关湍流研究的湍流螺旋性的信息。这使得很难通过采用螺旋度作为基本统计数量的湍流模型适当模拟湍流。在这项研究中，从湍流螺旋性的角度重新检查了湍流旋转流的代表性实验的数据。分析表明，哪种机制在产生湍流螺旋性方面主要是主要的。在实验中观察到的中心区域中高度不对称的均值谱图借助物理参数（例如旋流流的对称和保护特性）进行了校准。预计该校准的轮廓为湍流流量的数值模拟提供了牢固的基础。