ABSTRACT
Smart classrooms are a relatively confined public space for college students. SARS-COV-2 and other respiratory viruses have been shown to pose a more significant threat to human health in relatively confined spaces. Using numerical simulation method to simulate the transmission and concentration distribution of virus-carrying droplets in smart classrooms in three different seasons (summer, winter, transitional seasons: spring and autumn). The Realizable k-ε model is used to simulate the airflow pattern in the smart classroom, and the Lagrangian method is used to simulate the transmission of droplets. The transmission process of droplets produced from the teacher standing on the platform and the student sitting on the seat is studied. The influence of three kinds of outdoor temperature on droplet transmission and the body deposition fraction of people in the smart classroom is analyzed. The results show that droplet transmission speed is maximum at the temperature of 5 degrees when the outdoor temperature is 5 °C, 20 °C, and 35 °C respectively. At 10 s, the transmission distance of droplets increases by 9.55% compared with that at 20 °C and 10.31% compared with that at 35 °C. In addition, the body deposition fraction is also affected by the location of the vent, with downwind contact being 6 times more likely than upwind contact. The research results can provide suggestions and measures for epidemic prevention and control in smart classrooms.
ABSTRACT
In developing countries, public transportation is the first choice for the elderly because of its convenience and cheapness. The high density population of public transportation increases the risk of passengers contracting infectious diseases, so it is extremely critical to determine healthy transportation systems to safeguard the health of passengers. The propagation characteristics of droplets in the ZK-type public bus were studied by computational fluid simulation employing the Realizable k-ε turbulence model and discrete phase model. The modified Wells-Riley model was used to quantitatively assess the infection risk of SARS-CoV-2 spread by droplets on the elderly. The risk assessment shows that when the personalized air supply angle is 30°, the number of infected passengers is the least, reaching 14, which shows that the infection risk of passengers can be reduced through the design of personalized air supply angle. Regardless of the angle of the personalized air supply, the rear seats are in a low-risk area. Therefore, it's recommended that elderly passengers choose the rear seats of the public bus during the epidemic to prevent being infected. This study can provide a reference for healthy transportation systems to construct a healthy environment inside the public bus.
ABSTRACT
In closed buses, the spread of droplets with viruses/bacteria may cause the spread of respiratory infectious diseases. Discrete phase modeling is used to simulate the diffusion characteristics and concentration distribution of droplets at different temperatures and different exhalation positions by ANSYS FLUENT software. The integral concentration of droplets at different locations can be quantified, which leads to identification of low-risk areas and high-risk areas in the bus. Results show that a higher outdoor temperature leads to lower droplets’ diffusion speed and longer time until the droplets reach the driver. In addition, based on the integral concentration of droplets at the seats, regardless of whether a passenger exhales droplets in the front row of the bus, the position of the rear door or the last row of the bus, the seats in the last row of the bus away from the door belong to the low-risk area. In contrast, the seats near the door and the middle seat in the bus are higher risk areas. Consequently, this study proposed sitting on a seat in the low-risk area as a means to reduce the risk of passengers. Moreover, safety protection facilities around the driver should be modified to improve the isolation of the upper area of the driver’s location, so as to effectively prevent the droplet diffusion towards the driver, thereby effectively reducing the driver’s risk of infection.