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态相干结构。在轴向流中的旋转圆柱体上，它偏向速度曲线。这是三维的基本模型之一。湍流壁层，应视为包含身体力和额外应变速率的复杂湍流。今年，根据上一年获得的瞬时时间序列数据，使用VITA技术和四季度方法研究了爆发现象和湍流相干结构。 VITA分析的结果显示出波动速度信号的放大器的减少，间歇周期的降低以及爆发现象的检测到的频率下降。四季度方法的结果表明，近壁区域中扫荡事件的贡献比平板边界层的贡献相对较大。连续和离散的小波……还对圆柱平面内的局部平均速度方向以及垂直于该平面的速度成分进行了更多转换。连续小波变换的结果认识到小波光谱的峰值存在是继承现象。离散小波变换的结果表明，在波动速度的某些组成部分中存在高能光谱。通过在方位角沿两个位置的时间序列数据中获得了由高能核心流动和速度波动的跨频谱复合的速度成分。然后，从两点空间相关性获得侧光谱。结果表明，围绕旋转缸的大型螺旋涡流存在。作为数值分析的第一步，考虑了轴心界边界条件的层流流量分析以及基于K-ε模型和代数湍流模型的湍流分析。湍流分析的结果表明，很难充分预测提出的均值和波动流。目前，我们正在为低雷诺数字开发DNS代码，并在通道流中验证它。较少的