In the present work, we propose and demonstrate a simple experimental visualization to simulate sneezing by maintaining dynamic similarity to actual sneezing. A pulsed jet with Reynolds number Re = 30 000 is created using compressed air and a solenoid valve. Tracer particles are introduced in the flow to capture the emulated turbulent jet formed due to a sneeze. The visualization is accomplished using a camera and laser illumination. It is observed that a typical sneeze can travel up to 25 ft in ∼22 s in a quiescent environment. This highlights that the present widely accepted safe distance of 6 ft is highly underestimated, especially under the act of a sneeze. Our study demonstrates that a three-layer homemade mask is just adequate to impede the penetration of fine-sized particles, which may cause the spreading of the infectious pathogen responsible for COVID-19. However, a surgical mask cannot block the sneeze, and the sneeze particle can travel up to 2.5 ft. We strongly recommend using at least a three-layer homemade mask with a social distancing of 6 ft to combat the transmission of COVID-19 virus. In offices, we recommend the use of face masks and shields to prevent the spreading of droplets carrying the infectious pathogen. Interestingly, an N-95 mask blocks the sneeze in the forward direction; however, the leakage from the sides and top spreads the sneeze in the backward direction up to 2 ft. We strongly recommend using the elbow or hands to prevent droplet leakage even after wearing a mask during sneezing and coughing.

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The second and third waves of coronavirus disease-2019 (COVID-19) pandemic have hit the world. Even after more than a year, the economy is yet to return to a semblance of normality. The conference/meeting room is one of the critical sections of offices that might be difficult not to use. This study analyzes the distribution of the virus-laden droplets expelled by coughing inside a conference room, the effect of ventilation rates, and their positioning. The efficacy of masks is studied to get quantitative information regarding the residence time of the droplets. The effects of evaporation, turbulent dispersion, and external forces have been considered for calculating the droplets' trajectories. We have analyzed six cases, of which two are with masks. Change in the ventilation rate from four air changes per hour (ACH) to eight resulted in a 9% increment in the number of droplets entrained in the outlet vent, while their average residence time was reduced by ∼ 8 s. The shift in the vents' location has significantly altered droplets' distribution inside a conference room. It results in ∼ 1.5% of the injected droplets reaching persons sitting across the table, and a similar indoor environment is not recommended. Wearing a mask in the case of eight ACH has presented the best scenario out of the six cases, with a 6.5% improvement in the number of droplets entrained in the outlet vent and a 9 s decrease in their average residence time compared to the case without a mask. No droplets have reached persons sitting across the table when the infected person is wearing the mask, which follows that a social distancing of 6 ft with a mask is adequate in indoor environments.

The present work reports a computational study on the pitching of two identical NACA 0012 airfoils arranged in a side-by-side (parallel) configuration in a still medium. Pitching of airfoils arranged in a side-by-side (parallel) configuration in a still medium leads to the formation of a deflected jet. The angle at which the jet is deflected depends on the oscillation phase difference between the airfoils and the frequency of oscillation. The deflection angle is high at a lower frequency of oscillation for a given phase difference between the foils. The time-averaged jet deflection angle, thrust, and lift on airfoils are quantified for a range of frequencies (0.5 Hz–2 Hz) and phase differences (0°–180°) between the airfoils. The thrust force increases gradually with an increase in the phase difference between the foils until 120°, and beyond this, it decreases. The maximum jet deflection angle is found to be 28° when the phase difference is 45° for a frequency of 0.5 Hz. It is observed that the initially deflected jet switches toward the centerline position after specific periods of pitching. This switching of the jet from a deflected position toward the centerline initiates once the vortices from the lower foil interact completely with the upper foil. Some of these findings are relatively new in the domain of bio locomotion, which is useful for various related engineering applications.

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