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首页> 外文期刊>International Journal of Heat and Mass Transfer >Experimental study of human thermal plumes in a small space via large-scale TR PIV system
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Experimental study of human thermal plumes in a small space via large-scale TR PIV system

机译：大型TR PIV系统在狭小空间内人为热羽的实验研究

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摘要

In small occupied spaces such as vehicle cabins, in-depth information about human thermal plumes can be important for designing ventilation systems, especially in the case of displacement ventilation. In this study, large-scale time-resolved particle image velocimetry measurements were performed to reveal airflow characteristics of thermal plumes inside a small space with high temporal and spatial resolutions. The measured time-averaged velocity showed that the development of thermal plumes was limited by the small space, with maximum vertical velocity of 0.184 m/s above the head. The standard deviation of velocity and the turbulence intensity (TI) indicated high fluctuation characteristics, with TI of approximately 0.4 in the mainstream area. With these time-resolved data, the integral, Taylor and Kolmogorov scales were calculated, which provided recommended grid sizes and time steps for different numerical simulations. For investigation of instantaneous characteristics and vortex structures, three vortex identification parameters were compared. The vorticity index identified bulky attached and detached vortexes around the head; the Q-criterion revealed that the mainstream area was controlled mainly by deformation structures; and theλcicriterion, which was the most effective means of identification, avoided the influences of deformation structures and focused only on the rotation structures with directions of rotation. Furthermore, multi-scaled characteristics of thermal plumes were revealed by proper orthogonal decomposition, and the period of ascending plumes was estimated as 5 s.
机译：在狭窄的空间（如车厢）中，有关人为热羽的深入信息对于设计通风系统非常重要，尤其是在置换通风的情况下。在这项研究中，进行了大规模的时间分辨粒子图像测速仪测量，以揭示具有高时间和空间分辨率的小空间内热羽流的气流特征。测得的时间平均速度表明，热羽的发育受狭小空间的限制，在头部上方的最大垂直速度为0.184μm/ s。速度和湍流强度（TI）的标准偏差显示出较高的波动特性，主流区域的TI约为0.4。利用这些时间分辨数据，可以计算积分，泰勒和科莫格洛夫刻度，从而为不同的数值模拟提供建议的网格大小和时间步长。为了研究瞬时特性和涡旋结构，比较了三个涡旋识别参数。涡度指数表明头部周围有大的附着和分离的涡旋。 Q准则表明，主流区域主要由变形结构控制。最有效的识别手段是“判据”，它避免了变形结构的影响，只着眼于旋转方向的旋转结构。此外，通过适当的正交分解揭示了热羽的多尺度特征，估计羽的上升周期为5μs。

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