Purpose

This study aims (1) to numerically investigate the characteristics of a human cough jet in a quiescent environment, such as the variation with time of the velocity field, streamwise jet penetration and maximum jet width. Two different turbulence modelling approaches, the unsteady Reynolds-averaged Navier–Stokes (URANS) and large eddy simulation (LES), are used for comparison purposes. (2) To validate the numerical results with the experimental data.

Design/methodology/approach

Two different approaches, the URANS and LES, are used to simulate a human cough jet flow. The numerical results for the velocity magnitude contours and the spatial average of the two-dimensional velocity magnitude over the corresponding particle image velocimetry (PIV) field of view are compared with the relevant PIV measurements. Similarly, the numerical results for the streamwise velocity component at the hot-wire probe location are compared with the hot-wire anemometry (HWA) measurements. Furthermore, the numerical results for the streamwise jet penetration are compared with the data from the previous experimental work.

Findings

Based on the comparison with the URANS approach and the experimental data, the LES approach can predict the temporal development of a human cough jet reasonably well. In addition, the maximum width of the cough jet is found to grow practically linearly with time in the far-field, interrupted-jet stage, while the corresponding axial distance from the mouth of the jet front increases with time in an approximately quadratic manner.

Originality/value

Currently, no numerical study of human cough flow has been conducted using the LES approach due to the following challenges: (1) the computational cost is much higher than that of the URANS approach; (2) it is difficult to specify the turbulent fluctuations at the mouth for the cough jet properly; (3) it is necessary to define the appropriate conditions for the droplets to obtain statistically valid results. Therefore, this work fills this research gap.

中文翻译：

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人体咳嗽喷射器发展的数值模拟研究

目的

本研究旨在 (1) 对静止环境中人类咳嗽射流的特性进行数值研究，例如速度场随时间的变化、流向射流穿透和最大射流宽度。两种不同的湍流建模方法，非定常雷诺平均纳维-斯托克斯 (URANS) 和大涡模拟 (LES)，用于比较目的。(2)用实验数据验证数值结果。

设计/方法/方法

两种不同的方法，URANS 和 LES，用于模拟人类咳嗽喷射流。将相应粒子图像测速 (PIV) 视场上的速度幅度轮廓和二维速度幅度的空间平均值的数值结果与相关的 PIV 测量值进行比较。类似地，将热线探头位置处的流向速度分量的数值结果与热线风速计 (HWA) 测量值进行比较。此外，将流向射流穿透的数值结果与先前实验工作的数据进行了比较。

发现

基于与 URANS 方法的比较和实验数据，LES 方法可以较好地预测人类咳嗽喷射的时间发展。此外，在远场、间断射流阶段，咳嗽射流的最大宽度几乎随时间线性增长，而与射流锋口的相应轴向距离以近似二次方的方式随时间增加。

原创性/价值

目前，由于以下挑战，尚未使用 LES 方法对人体咳嗽流量进行数值研究：（1）计算成本远高于 URANS 方法；(2) 咳嗽喷射口的湍流波动难以准确确定；(3) 有必要为液滴定义适当的条件以获得统计上有效的结果。因此，这项工作填补了这一研究空白。