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Experimental and numerical studies for a dynamical coherent structure of the skewed turbulent boundary layer on a rotating cylinder

旋转圆柱体上倾斜湍流边界层动力学相干结构的实验和数值研究

基本信息

批准号：
14550144
负责人：
YAMASHITA Shintaro
金额：
$ 2.37万
依托单位：
Gifu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

The objective of the present study is to understand a dynamical coherent structure of a turbulent boundary layer. which has skewed velocity profiles, on a rotating cylinder in an axial flow. This is one of the basic models of a three-dimensional. turbulent wall layer, which should be treated as a complicated turbulent flow containing body force and extra strain rate.This year, the bursting phenomena and the turbulent coherent structure were investigated using VITA technique and four-quadrant method according to the instantaneous time series data obtained the previous year. The results of the VITA analysis exhibit a decrease in amplitude of the fluctuating velocity signal, reduction of the intermittent period and a decrease in the detected frequency of the bursting phenomena. The results of the four-quadrant method exhibit that the contributions of a sweep event in the near wall region become relatively larger than those of the flat plate boundary layer. Continuous and discrete wavelet … More transform were also performed to the fluctuating velocity components in the local mean velocity direction within the cylindrical plane, and to the velocity components perpendicular to that plane. The results of the continuous wavelet transform recognized the existence of the peak of wavelet spectra as inherent phenomena. The results of discrete wavelet transform exhibit that there are high-energy spectra in some components of the fluctuating velocity. The velocity components recomposed by high-energy coefficient exhibit distinct. negative correlation.Two-point space-time correlation and cross-spectra of velocity fluctuations were obtained from time series data at two positions in the azimuthal direction. Then, lateral spectra were obtained from two-point space correlations. The results suggest the existence of large scale helical eddies surrounding the rotating cylinder.As a first step of numerical analysis, laminar flow analysis considering axisymmetric boundary condition, and turbulent flow analysis based on a k-ε model and algebraic turbulence model, were conducted. The results of turbulent flow analysis show that it is difficult to predict sufficiently both the mean and fluctuating flow filed. At present, we are developing a DNS code for low Reynolds number and verifying it in a channel flow. Less

本研究的目的是了解湍流边界层的动力学相干结构。其具有偏斜的速度分布。这是一个三维的基本模型。湍流壁层是一个包含体积力和附加应变率的复杂湍流流动，本年度利用VITA技术和四象限法，根据前一年的瞬时时间序列资料，研究了突爆现象和湍流拟序结构。VITA分析的结果表明，脉动速度信号的幅度减小，间歇周期减小，检测到的爆裂现象的频率减小。四象限方法的计算结果表明，在近壁区，后掠事件的贡献比平板边界层的贡献大。连续和离散小波 ...更多信息对圆柱面内局部平均速度方向上的脉动速度分量和垂直于该平面的速度分量进行了变换。连续小波变换的结果确认了小波谱峰值的存在是固有现象。离散小波变换的结果表明，脉动速度的某些分量存在高能谱。高能系数重构后的速度分量表现出明显的特征。负相关。两点的时空相关和交叉谱的速度波动的时间序列数据得到在两个位置上的方位角方向。通过两点空间相关得到了横向谱。作为数值分析的第一步，首先进行了考虑轴对称边界条件的层流流动分析，以及基于k-ε模型和代数湍流模型的湍流流动分析。湍流分析结果表明，无论是平均流场还是脉动流场都很难得到充分的预测。目前，我们正在开发一个适用于低雷诺数的DNS程序，并在槽道流中进行验证。少