Kang Yeeun, Park Jooyeon, Park Hyungmin
Department of Mechanical Engineering, Seoul National University, Seoul 08826, Korea.
Phys Fluids (1994). 2021 Oct;33(10):103326. doi: 10.1063/5.0067174. Epub 2021 Oct 25.
In today's era of active personal protections against airborne respiratory disease, general interest in the multiphase flow physics underlying face masks is greater than ever. The exhalation valves, installed on some masks to mitigate the breathing resistance, have also received more attention. However, the current certification protocol of evaluating airflow leakage only when suction pressure is applied is insufficient to capture practical aspects (particle penetration or leakage). Here, we experimentally measure two-phase flow across valve-type masks under conditions mimicking actual breathing. During exhalation, a high-speed jet through the valve accelerates the transmission of particles from inside while reasonable protection from external pollutants is achieved during inhalation, which supports the warnings from various public health officials. Based on the mechanism of particle penetration found here, we hope a novel design that both achieves high-efficiency shielding and facilitates easy breathing can be developed.
在当今积极进行空气传播呼吸道疾病个人防护的时代，人们对口罩背后的多相流物理原理的普遍兴趣比以往任何时候都要浓厚。安装在一些口罩上以减轻呼吸阻力的呼气阀也受到了更多关注。然而，当前仅在施加吸气压力时评估气流泄漏的认证协议不足以涵盖实际情况（颗粒穿透或泄漏）。在此，我们在模拟实际呼吸的条件下，通过实验测量了穿过阀式口罩的两相流。呼气时，通过阀门的高速射流加速了内部颗粒的传播，而在吸气时则能对外部污染物实现合理防护，这支持了各位公共卫生官员的警告。基于此处发现的颗粒穿透机制，我们希望能够开发出一种既能实现高效防护又便于呼吸的新型设计。
