Turbulence structure of a boundary layer beneath a turbulent free stream
Turbulence structure of a boundary layer beneath a turbulent free stream
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湍流自由流下边界层的湍流结构
DOI：
10.1017/s0022112089001941
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发表时间：
1989
影响因子：
3.7
通讯作者：
P. Bradshaw
中科院分区：
文献类型：
--
作者：
P. Hancock;P. Bradshaw
在平板上的湍流边界层中，在网格产生的自由流的存在下进行了测量，湍流具有广泛的长度尺度。数据包括有条件采样的平均值，其中自由流流体被区分从边界层流体加热后者。自由流湍流增加的标准偏差的冷热界面的边界层厚度的比例，而平均位置主要取决于长度尺度。边界层流体的剪切相关系数减小，表明结构的变化与脉动应变率直接相关。代表湍流动能和剪切应力扩散的传输速度在边界层流体中与自由流流体中的传输速度具有相反的符号，并且它们也与波动应变率有关。计算了湍流动能和剪应力的完全平衡，通过差分推导出耗散和压力-应变重分布。耗散长度尺度L\tau =（-\overline{uv}）^{\frac{3}{2}}/\endash $受自由流湍流的影响很小，而相应的基于湍流能量而不是剪切应力的参数受到强烈影响。
Measurements have been made in the turbulent boundary layer on a flat plate in the presence of grid-generated free-stream, turbulence with a wide range of lengthscales. The data include conditionally sampled averages in which free-stream fluid was distinguished from boundary-layer fluid by heating the latter. Free-stream turbulence increases the standard deviation of the hot–cold interface as a proportion of the boundary-layer thickness, whilst the average position is mainly dependent upon the lengthscale. The shear correlation coefficient of the boundary-layer fluid decreases, and it is shown that the change in structure is directly related to the fluctuating-strain rate. Transport velocities representing the diffusion of turbulent kinetic energy and shear stress have opposite signs in the boundary-layer fluid to those in the free-stream fluid, and it is shown that they are also related to the fluctuating-strain rate. Complete balances of turbulent kinetic energy and shear stress have been evaluated, dissipation and pressure–strain redistribution having been deduced by difference. The dissipation length scale $L\tau = (-\overline{uv})^{\frac{3}{2}}/\epsilon $ is little affected by free-stream turbulence, whereas the corresponding parameter based on turbulent energy instead of shear stress is strongly affected.