The coronavirus disease outbreak of 2019 has been causing significant loss of life and unprecedented economic loss throughout the world. Social distancing and face masks are widely recommended around the globe to protect others and prevent the spread of the virus through breathing, coughing, and sneezing. To expand the scientific underpinnings of such recommendations, we carry out high-fidelity computational fluid dynamics simulations of unprecedented resolution and realism to elucidate the underlying physics of saliva particulate transport during human cough with and without facial masks. Our simulations (a) are carried out under both a stagnant ambient flow (indoor) and a mild unidirectional breeze (outdoor), (b) incorporate the effect of human anatomy on the flow, (c) account for both medical and non-medical grade masks, and (d) consider a wide spectrum of particulate sizes, ranging from 10 µm to 300 µm. We show that during indoor coughing some saliva particulates could travel up to 0.48 m, 0.73 m, and 2.62 m for the cases with medical grade, non-medical grade, and without facial masks, respectively. Thus, in indoor environments, either medical or non-medical grade facial masks can successfully limit the spreading of saliva particulates to others. Under outdoor conditions with a unidirectional mild breeze, however, leakage flow through the mask can cause saliva particulates to be entrained into the energetic shear layers around the body and transported very fast at large distances by the turbulent flow, thus limiting the effectiveness of facial masks.

中文翻译：

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流体动力学模拟表明，面膜可抑制COVID-19在室内环境中的扩散

2019年的冠状病毒疾病爆发已在全世界造成严重的生命损失和前所未有的经济损失。在全球范围内广泛建议使用社交隔离和口罩，以保护他人并通过呼吸，咳嗽和打喷嚏防止病毒传播。为了扩展此类建议的科学依据，我们进行了前所未有的分辨率和逼真度的高保真计算流体动力学模拟，以阐明在有或没有面罩的情况下人咳嗽过程中唾液微粒运输的基本原理。我们的模拟（a）在停滞的环境流量（室内）和温和的单向微风（室外）下进行，（b）结合人体解剖学对流量的影响，（c）考虑到医学和非医学方面的影响口罩μ m至300 μ米。我们发现，在室内咳嗽期间，对于医用级，非医用级和没有面罩的患者，某些唾液颗粒可能分别传播至0.48 m，0.73 m和2.62 m。因此，在室内环境中，医用或非医用等级的口罩都可以成功地限制唾液颗粒向他人的扩散。但是，在室外空气单向微风的情况下，通过面罩的泄漏流会导致唾液颗粒被带入人体周围的高能剪切层，并在湍流的作用下在很长的距离内非常快速地运输，从而限制了面罩的有效性。