Disturbance growth in boundary layers subjected to free-stream turbulence
Disturbance growth in boundary layers subjected to free-stream turbulence
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DOI：
10.1017/s0022112000002810
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发表时间：
2001-03-10
影响因子：
3.7
通讯作者：
Alfredsson, PH
中科院分区：
文献类型：
--
作者：
Matsubara, M;Alfredsson, PH
本文旨在描述边界层流动，该边界层流动受到 1-6% 范围内的自由流湍流的影响，并基于流动可视化结果和广泛的热线测量。这种流动会形成高流向速度和低流向速度的流向拉长区域，这似乎会导致二次不稳定并分解为湍流。研究发现条纹结构的初始生长与代数或瞬态生长理论密切相关。这些数据已用于确定条纹结构的流向和展向尺度。流动可视化和热线测量都表明，与边界层厚度相比，靠近前缘的展向尺度较大，但在下游，展向尺度接近边界层厚度。计算了流向和翼展方向上的波数谱。发现了扰动的流向结构的缩放，这使得我们能够折叠来自不同下游位置的光谱。缩放结合了以下事实：条纹结构在下游方向增加其流向长度，这与边界层厚度成正比，并且能量增长是代数的，接近与下游距离成正比。
This paper aims at a description of boundary-layer flow which is subjected to freestream turbulence in the range from 1-6% and is based on both flow visualization results and extensive hot-wire measurements. Such flows develop streamwise elongated regions of high and low streamwise velocity which seem to lead to secondary instability and breakdown to turbulence. The initial growth of the streaky structures is found to be closely related to algebraic or transient growth theory. The data have been used to determine streamwise and spanwise scales of the streaky structures. Both the flow visualization and the hot-wire measurements show that close to the leading edge the spanwise scale is large as compared to the boundary-layer thickness, but further downstream the spanwise scale approaches the boundary-layer thickness. Wavenumber spectra in both the streamwise and the spanwise directions were calculated. A scaling for the streamwise structure of the disturbance was found, which allows us to collapse the spectra from different downstream positions. The scaling combines the facts that the streaky structures increase their streamwise length in the downstream direction which becomes proportional to the boundary-layer thickness and that the energy growth is algebraic, close to proportional to the downstream distance.