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首页> 外文期刊>Journal of Fluid Mechanics >Statistical structure of momentum sources and sinks in the outer region of a turbulent boundary layer
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Statistical structure of momentum sources and sinks in the outer region of a turbulent boundary layer

机译：湍流边界层外部区域动量源和汇的统计结构

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摘要

The spatial structure of momentum sources and sinks (T > 0 and T < 0; where T is the streamwise component of the Lamb vector) is examined in a turbulent boundary layer by using dual-plane particle image velocimetry data obtained in streamwise-spanwise planes at two wall-normal locations (x(2)/delta = 0.1 and 0.5, where x(2) is the wall-normal location and delta is the boundary layer thickness). Two-point correlations of T indicate that the size of source motions remains relatively constant while the size of sink motions increases with increasing wall-normal distance. The relative strength of sink motions also increases away from the wall. The velocity field in the vicinity of source/sink motions was explored by computing cross-correlations of T with the velocity components. Source-like motions are correlated with elongated low-momentum zones that possess regions of upwash embedded within them and appear to be the strongest in areas where these low-momentum zones meander in the spanwise direction. Momentum sinks appear to be located within low-speed regions that are within larger high-momentum zones. The velocity fluctuations undergo rapid transitions between quadrants in the vicinity of sinks (i.e. both streamwise and wall-normal velocity fluctuations change sign). The length scales, over which the fluctuations change sign, are much larger at x(2)/delta = 0.5 than at x(2)/delta = 0.1.
机译：使用在水流跨度平面中获得的双平面粒子图像测速数据，在湍流边界层中检查了动量源和汇的空间结构（T> 0和T <0;其中T是Lamb向量的水流分量）在两个壁法线位置（x（2）/ delta = 0.1和0.5，其中x（2）是壁法线位置，而delta是边界层厚度）。 T的两点相关性表明，源运动的大小保持相对恒定，而水槽运动的大小随着壁法向距离的增加而增加。水槽运动的相对强度也远离墙壁而增加。通过计算T与速度分量的互相关性，探索了源/汇运动附近的速度场。类似源的运动与细长的低动量区域相关，该区域具有嵌入其中的上冲区域，并且在这些低动量区域沿展向方向蜿蜒的区域中表现出最强的运动。动量汇似乎位于较大高动量区域内的低速区域内。速度波动在水槽附近的象限之间经历快速过渡（即沿河向和壁法向速度波动都改变符号）。在x（2）/ delta = 0.5时，波动变化符号的长度标度比在x（2）/ delta = 0.1时的标度大得多。

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