AN EXPERIMENTAL STUDY ON 1/f^<tx> STRUCTRE AND ENTRAINMENT IN TURBULENT BOUNDARY LAYER

湍流边界层1/f^<tx>结构和夹带的实验研究

• 批准号: 13650182
• 负责人: MOCHIZUKI Shinsuke
• 金额: $ 2.3万
• 依托单位: Yamaguchi University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650182/
• 关键词: Turbulent Boundary Layer; Entrainment; Coherent Structure; Fractals; Equilibrium Boundary Layer

In the present study, entrainment mechanisms associated with large scale eddies in turbulent boundary layers has been investigated in terms of 1/f^<tx> intermittent nature defined in fractals. The experiment has been made in a flat plate boundary layer and a self-preserving boundary layer developed under power-law variation of the free-stream. The free-stream is decelerating with x^<-0.188> for the self-preserving boundary layer, thus the boundary layer is subjected to a mild adverse pressure gradient.A new direct measurement device for the local wall shear stress has been developed and applied in the present experimental study. The measurement device has 20mm circular friction surface and zero-displacement circuit that keeps the floating element at initial position. Application of the new device to the flat plate boundary layer proves that the wall shear stress can be obtained experimentally with sufficiently high accuracy and reliability.In both the boundary layers, the mean velocity profile near the wall can be reasonably expressed in the logarithmic mean velocity profile with Karman constant of 0.41 and additive constant of 5.0. Strength of wake component in the outer layer mean velocity profile is strongly enlarged by the adverse pressure gradient. The triple velocity products, which mean turbulence diffusion of Reynolds shear stresses and turbulent intensity, become greater in magnitude of absolute values.The outer layer intermittent nature has been investigated by conditional sampling technique that is applied to recognize turbulent and non-turbulent zones. Two-point double velocity correlation functions were calculated for turbulent zone and non-turbulent zone, respectively. A large scale streamwise vortical motion is expected in turbulent bulge and spanwise size of the vortical motion is squeezed by the adverse pressure gradient. The probability of streamwise interval of turbulent can be successfully explained by power-law functions.

在本研究中，与湍流边界层中的大尺度涡相关的卷吸机制已经根据分形中定义的1/f^间歇性质进行了研究<tx>。实验是在平板边界层和幂律变化自由流条件下形成的自保持边界层中进行的。本文<-0.188>介绍了一种新的壁面切应力直接测量装置，并将其应用于实验研究。测量装置具有20 mm的圆形摩擦面和使浮动元件保持在初始位置的零位移电路。将该装置应用于平板边界层，实验结果表明，壁面切应力的测量具有足够高的精度和可靠性，在两种边界层中，近壁面平均速度分布都可以用卡门常数为0.41、附加常数为5.0的对数平均速度分布合理地表示。逆压梯度使外层平均速度廓线中的尾流分量的强度显著增大。雷诺切应力和湍流强度的湍流扩散的三重速度积在绝对值上变大，用条件采样技术研究了外层的间歇性，该技术用于识别湍流区和非湍流区。分别计算了湍流区和非湍流区的两点双速度相关函数。在湍流鼓包区存在大尺度的流向涡运动，而涡运动的展向尺度被逆压梯度压缩。幂律函数可以成功地解释湍流流向间隔的概率。

项目成果

Shinsuke Mochizuki: "The Mean Flow Quantities in an Equilibrium Boundary Layer Subjected to the Adverse Pressure Gradient"Proceedings of 2002 Annual Meeting of Japan Society of Mechanical Engineers. Vol.02, No.1. 75-76 (2002)

Shinsuke Mochizuki：“受逆压力梯度影响的平衡边界层中的平均流量”日本机械工程学会 2002 年年会论文集。

小濱大輔: "壁面せん断応力の直接測定に関する研究"日本機械学会2001年度年次大会講演論文集. 01・1. 215-216 (2001)

小滨大辅：“壁面剪切应力的直接测量研究”日本机械工程学会2001年年会论文集01・1（2001）。

亀田孝嗣: "乱流境界層の外層領域における平均速度分布の相似性"日本機械学会論文集B編. 67・660. 1975-1982 (2001)

Takaji Kameda：“湍流边界层外层区域的平均速度分布的相似性”，日本机械工程学会会刊，B 版，1975-1982 年（2001 年）。

Takatsugu Kameda: "The Similarity of the Velocity Defect Profile for the Outer Layer in Smooth Wall and Rough Wall Turbulent Boundary Layers"Transactions of Japan Society of Mechanical Engineers. Vol.67, No.660. 1975-1982 (2001)

Takatsugu Kameda：“光滑壁和粗糙壁湍流边界层外层速度缺陷轮廓的相似性”日本机械工程学会会刊。

Shinsuke Mochizuki: "An Experimental Study of a Self-preserving Boundary Layer with A Power-law Variation of Free-stream Velocity"IUTAM Symposium on Reynolds Number Scaling in Turbulent Flow. 606.1-606.2 (2002)

Shinsuke Mochizuki：“自由流速度幂律变化的自保边界层的实验研究”IUTAM 湍流雷诺数缩放研讨会。