【作者】 王瑞新；

【导师】 姜楠；

【作者基本信息】 天津大学 ， 流体力学， 2006， 硕士

【摘要】 本文以平板湍流边界层为实验研究对象,以湍流大涡模拟尺度相似亚格子模型中速度大小尺度成份间相似性假设u i′uj′≈ui′uj′=(u i-ui)(uj-uj)为研究内容,研究了平板湍流边界层多尺度相干结构对大涡模拟亚格子尺度模型的影响。首先用IFA300热线风速仪以高于最小湍流结构对应时间尺度的分辨率,精细测量风洞中低、中、高三个不同雷诺数下平板湍流边界层不同法向位置流向速度分量的时间序列信号,并对平板湍流边界层无量纲化的平均速度剖面进行检验。然后对实验测量得到的原始速度信号用子波分析进行多尺度分解,得到不同时间尺度下的子波系数,对该子波系数进行反演变换得到不同尺度的脉动速度信号,再通过低通滤波的方法得到湍流分尺度雷诺应力项和分尺度脉动速度乘积,通过计算湍流分尺度雷诺应力项和分尺度脉动速度乘积的互相关系数随尺度参数的变化规律,研究尺度相似亚格子模型的适用尺度范围以及尺度相似亚格子模型沿平板湍流边界层法向的变化规律。用检测湍流多尺度相干结构的条件采样方法将壁湍流信号中的多尺度相干结构成份与非相干成份分离,将此信号分解为两部分:一部分是检测出的局部多尺度相干结构信号,另一部分是去除相干结构以后非相干成份的信号,分别对两组信号采用上述方法重新进行湍流分尺度雷诺应力和分尺度脉动速度乘积的尺度互相关分析,比较去除多尺度相干结构成份前后尺度互相关系数的变化规律,分析平板湍流边界层近壁区域多尺度相干结构对大涡模拟尺度相似亚格子尺度模型的影响,研究多尺度相干结在湍流不同尺度间动量、能量传递的作用。更多还原

【Abstract】 The influence on LES sub-grid scale model, by multi-scale coherent eddy structures in the near wall region of turbulent boundary layer, is studied, on the basis of scale similar hypothesis on LES sub-grid model.The experimental investigation for LES scale similar sub-grid model is carried out in a wind tunnel with IFA300 constant-temperature anemometer. The time sequence of longitudinal velocity component at different vertical locations in turbulent boundary layer, at low, middle and high Reynolds numbers, was finely measured respectively, with temporal resolution higher than the frequency corresponding to Kolmogorov dissipation scale. Mean flow field of turbulent boundary layer is verified by dimensionless logarithm law mean velocity profile.Fluctuating velocity signals, at different temporal scales, are acquired, after primal signals are decomposed by wavelet transfer and inverse transfer successively on the basis of multi-scale resolution theory. Multi-scale Reynolds normal stress, the left term of scale similar hypothesis formulation, and the right terms, are obtained through low-pass filtering multi-scale fluctuating velocity signals. The correlation factors between the two sides of formulation are found to be different from scale to scale. Then, the valid scale rang of scale-similar sub-grid model is studied further, as well as its evolution at vertical locations in turbulent boundary layer.Multi-scale coherent eddy structures are eliminated from turbulent velocity signals by conditional sampling method, and the velocity signals, including and excluding coherent eddy structures, are acquired. The changes on correlation factors, before and after multi-scale coherent eddy structures have been eliminated, is obtained. The influence of coherent eddy structures, especially for the near wall region of turbulent boundary layer, on LES scale- similar sub-grid model, is studied.更多还原