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.

No abstract

It is necessary to explore the effects of airflow in moving elevator cars on the diffusion of droplet nuclei and evaluate inhalation and touching risks due to the elevator car being a place where dangerous respiratory diseases can spread. A realizable k–ε turbulence model and discrete phase model were applied with gas–solid multiphase modeling principles to simulate the diffusion of droplet nuclei generated by coughs in a moving elevator. Four cases are discussed with differences in the elevator motion direction and air supply system. The results show that the elevator movement causes the airflow direction in respiratory regions to change by more than 30°, which is more evident in the absence of air supply. Under the combined effects of the airflow supply and the thermal plume, the high-temperature zone became a gathering point for droplet nuclei. The upward elevator movement increases the inhalation risk of a passenger who stands farther from an index patient and has the highest inhalation risk about 4.4 × 10−19. The downward movement increases the duration to about 40 s, for which that passenger remains at the highest risk. The area in front of the patient is the highest touching risk area, especially for downward motion. In addition, the button area is a high-risk area for touching because about 4% of cough droplet nuclei are deposited there. This may spread viable viruses if passengers touch the buttons, even if the coughing person is no longer in the elevator. Thus, elevator cars need to be regularly disinfected, especially the button area.

No abstract

The venturi scrubber is one of the most efficient gas cleaning devices for removal of contaminating particles in industrial flue-gas purification processes. The velocity of the gas entering the scrubber is one of the key factors influencing its dust-removal efficiency. In this study, the shapes of the heavy mound and tube wall are optimized, allowing the girth area to become linearly adjustable. The resulting uniformity of velocity distribution is verified numerically.