This work presents a detailed study of the turbulence flow statistics of a jet mounted with its axis parallel to a rigid flat plate. Hot-wire constant temperature anemometry has been used to measure the single-point and two-point statistics of the axial velocity component at several locations within the jet flow field. Results show that the jet mean flow near the plate surface is subjected to a local acceleration and redirection due to a Coandă-type effect. The propagation of these effects downstream of the plate trailing edge is strongly dependent on the plate position. Regarding the velocity fluctuations, the mean turbulence intensity levels are seen to decrease as the radial distance between the jet and surface decreases. Analysis of the single-point power spectral density data on the shear layer close to the plate shows that the reduction in magnitude of the low-frequency content of the energy spectrum is responsible for the decrease in turbulence intensity. Additionally, the characteristic time and length scales computed from two-point measurements reduce as the plate is mounted closer to the jet centre-line. The axial eddy convection velocity is seen to increase in the region of high turbulent kinetic energy in the shear layer adjacent to the surface. Empirical models for turbulence characteristic scales and eddy convection velocity are presented. These findings suggest that both the amplitude and distribution of the jet mixing noise sources are affected when closely installed next to a surface. This paper is a continuation of a recent investigation on the turbulence statistics of isolated jets presented in Proenca (Exp Fluids 60(4):63, 2019).

中文翻译：

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使用热线风速测量法研究已安装射流的湍流统计

这项工作详细研究了喷流的湍流统计，喷流的轴平行于刚性平板。热线恒温风速测量法已被用于测量射流场内多个位置的轴向速度分量的单点和两点统计。结果表明，由于 Coandă 型效应，板表面附近的射流平均流受到局部加速和重定向。这些效应在板块后缘下游的传播很大程度上取决于板块位置。关于速度波动，平均湍流强度水平随着射流和表面之间的径向距离的减小而减小。对靠近板块的剪切层的单点功率谱密度数据的分析表明，能谱低频成分的幅度减小是湍流强度减小的原因。此外，当板安装得更靠近喷射中心线时，从两点测量计算的特征时间和长度尺度会减少。轴向涡流对流速度在与表面相邻的剪切层中的高湍流动能区域中增加。提出了湍流特征尺度和涡流对流速度的经验模型。这些发现表明，当靠近表面安装时，射流混合噪声源的幅度和分布都会受到影响。