Abstract This work aims to understand the difference in the correlations between the fluctuating temperature and the vorticity from that between the fluctuating temperature and the velocity in a turbulent cylinder near wake. Measurements are made at x/d = 10, 20 and 40, where x is the streamwise distance from the cylinder axis and d is the cylinder diameter, with a Reynolds number of 2.5×103 based on d and the free-stream velocity. The three components of the fluctuating velocity vector ui(i = 1, 2 and 3), vorticity vector ωi (i = 1, 2 and 3), and temperature θ in the plane of the mean shear are measured simultaneously with a multi-wire probe consisting of four X-hotwires and four cold wires. It is found that at x/d = 10, both correlations between uiand θ and between ωi and θ predominantly take place at St = 0.21, due to the concentric distribution of the Karman vortices and the heat. With increasing x/d, the correlation between ωi (i = 1, 2 and 3) and θ drops rapidly, as a result of the weakened Karman vortices; in contrast, the correlation between u1 and θ increases appreciably, largely due to an enhanced correlation between u1 and θ at low frequencies or scales of motions larger than the Karman vortex. The slowly decreasing (along x) two-point autocorrelations of u1 and θ suggest that the very-large-scale motions (VLSMs) found in wall flows occur also in the turbulent wake and are responsible for the high correlation between u1 and θ at low frequencies.

中文翻译：

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湍流圆柱尾流中温度与涡度和速度的相关性

摘要 这项工作旨在了解脉动温度与涡度之间的相关性与脉动温度与尾流附近湍流圆柱体中速度之间的相关性的差异。在 x/d = 10、20 和 40 处进行测量，其中 x 是距圆柱轴的流向距离，d 是圆柱直径，基于 d 和自由流速度，雷诺数为 2.5×103。用多线同时测量波动速度矢量 ui(i = 1、2 和 3)、涡度矢量 ωi (i = 1、2 和 3) 和平均剪切平面内的温度 θ 的三个分量探头由四根 X 热线和四根冷线组成。发现在 x/d = 10 处，ui 和 θ 之间以及 ωi 和 θ 之间的相关性主要发生在 St = 0.21 处，由于卡门涡旋和热量的同心分布。随着 x/d 的增加，由于卡门涡旋减弱，ωi（i = 1、2 和 3）与 θ 之间的相关性迅速下降；相比之下，u1 和 θ 之间的相关性显着增加，主要是由于 u1 和 θ 在低频或大于卡门涡旋的运动尺度下增强了相关性。u1 和 θ 的缓慢下降（沿 x）两点自相关表明壁流中发现的超大规模运动 (VLSM) 也发生在湍流尾流中，并且导致 u1 和 θ 在低频率。u1 和 θ 之间的相关性显着增加，主要是由于 u1 和 θ 在低频或大于卡门涡旋的运动尺度下增强了相关性。u1 和 θ 的缓慢下降（沿 x）两点自相关表明壁流中发现的超大规模运动 (VLSM) 也发生在湍流尾流中，并且导致 u1 和 θ 在低频率。u1 和 θ 之间的相关性显着增加，主要是由于 u1 和 θ 在低频或大于卡门涡旋的运动尺度下增强了相关性。u1 和 θ 的缓慢下降（沿 x）两点自相关表明壁流中发现的超大规模运动 (VLSM) 也发生在湍流尾流中，并且导致 u1 和 θ 在低频率。