Mean momentum balance in moderately favourable pressure gradient turbulent boundary layers
Mean momentum balance in moderately favourable pressure gradient turbulent boundary layers
复制标题
适度有利压力梯度湍流边界层中的平均动量平衡
DOI：
10.1017/s0022112008003637
复制
发表时间：
2008
影响因子：
3.7
通讯作者：
P. Fife
中科院分区：
文献类型：
--
作者：
M. Metzger;A. Lyons;P. Fife
在基于未积分二维平均动量方程的理论框架内研究了中等有利压力梯度湍流边界层。目前的理论源于在边界层不同区域的平均动量方程中所观察到的平衡交换。这种平衡的交换导致不同物理层的识别，由每层中活动的主要平均动力学明确定义。通过对平均动量方程的多尺度分析，得到了与物理层一致的尺度域。对于长发展长度风洞中产生的沉流压力梯度，利用直接测量平均动量平衡中的所有项来评估本理论预测的标度行为。测量还捕获了湍流边界层从风洞入口附近的非平衡状态向进一步下游的平衡状态的演变。所有实验数据都再现了当前多尺度理论的显著特征。在平衡条件下，发现了一个通用函数来描述边界层外区域雷诺应力剖面的衰减。非平衡效应似乎主要表现在外部区域，而内部区域的差异完全归因于雷诺数效应。
Moderately favourable pressure gradient turbulent boundary layers are investigated within a theoretical framework based on the unintegrated two-dimensional mean momentum equation. The present theory stems from an observed exchange of balance between terms in the mean momentum equation across different regions of the boundary layer. This exchange of balance leads to the identification of distinct physical layers, unambiguously defined by the predominant mean dynamics active in each layer. Scaling domains congruent with the physical layers are obtained from a multi-scale analysis of the mean momentum equation. Scaling behaviours predicted by the present theory are evaluated using direct measurements of all of the terms in the mean momentum balance for the case of a sink-flow pressure gradient generated in a wind tunnel with a long development length. Measurements also captured the evolution of the turbulent boundary layers from a non-equilibrium state near the wind tunnel entrance towards an equilibrium state further downstream. Salient features of the present multi-scale theory were reproduced in all the experimental data. Under equilibrium conditions, a universal function was found to describe the decay of the Reynolds stress profile in the outer region of the boundary layer. Non-equilibrium effects appeared to be manifest primarily in the outer region, whereas differences in the inner region were attributed solely to Reynolds number effects.