Physics of Fluids: Repeated coughing may significantly reduce the protective performance of masks.

July 19, 2020 // Wearing a mask is thought to slow the spread of the virus, including the SARS-CoV-2 virus that causes COVID-19, but little seems to be known about how masks work better; in a recent study published in the international journal Physics of Fluids, scientists from the University of Nicosia and others successfully mapped the flow of small drops released by people wearing masks when they cough repeatedly using accurate computer modelsPhoto Source: Talib Dbouk and Dimitris Drikakis Previously researchers have found that when a person who is not wearing a mask coughs, its saliva droplets can spread 18 feet (about 5.5 meters) in five seconds, and the new study uses an expanded model to analyze the effects and effects of wearing a mask and multiple coughsThe results suggest that masks reduce the spread of air droplets, but repeated coughing or negatively affecting the effectiveness of the mask, as can occur when a person is ill, repeated coughing reduces the efficiency of the mask and allows more droplets to spread through the maskUsing complex mathematical equations of turbulence and other flow effects, the researchers modeled the new model by applying several cycles of normal velocity pulses to the initial droplets to simulate a series of repeated coughs, allowing them to simulate the interaction between droplets and the multiple-air filters of the shell mask; During the period, some droplets can also spread to a considerable distance, and up to 1 meter, however, if you do not wear a mask, droplets will fly to two times the distance, so wearing a mask may be effective in preventing the spread of droplets, and wearing a mask can also reduce the number of leakage droplets from the side of the mask, but not completely eliminate dropletsThese calculations also reveal the effects of the droplet size due to turbulence encountering masks, escapes and entry into the environment, and researcher Drikakis said that during coughing, the size of the droplets changes and fluctuates due to the multiple interactions between the mask and the face; The use of masks does not provide complete protection, so the social distance between people is still important, and for health care workers, investigators should be equipped with more complete personal protective equipment, including helmets with built-in air filters, face masks, disposable protective clothing and double glovesThe researchers should also urge manufacturers and regulators to consider using the latest standards to evaluate the performance of masks, including fluid physics and cough dynamics, and the latest standards for evaluating the performance of masksOriginal origins: Talib Dbouk, Dimitris DrikakisOn-the-airway droplets and face masks, Physics of Fluids (2020) doi: 10.1063/5.0015044.