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 importance of renewable energy has increased continuously in the recent years due to the growth in the energy demand and a decrease in the fossil fuel resources. Harnessing the low rated wind energy is the promising source so that the wind turbine can be used all year round. Deploying sequence of small turbine is efficient than single bigger size turbine in extracting the low rated wind energy. Hence, in this work, sequence of small vertical axis wind turbine is arranged in the tree like structure and named it as wind tree. The vertical axis type of turbine would be able to perform more efficiently at minimum wind velocity. So, the Helical Savonius vertical axis rotor is deployed in the wind tree which gives the relatively high torque and self-starting even at low wind speeds. The main aim of this work is to analyze numerically the cluster of vertical axis wind turbine in order to improve the average output of the wind tree. In this study, the vertical axis turbines are arranged in the branches of the tree at different plane, so that the wake of one turbine will not affect the turbine in the downstream. The numerical simulation has been studied by using commercially available software ANSYS CFX©. The single helical vertical axis wind turbine is fabricated and tested in the open jet wind tunnel and this experimental result is used for validating the numerical results. In addition to the validation, sensitive study for the grid and the turbulence model has been carried out to improve the simulation quality. Vertical axis wind can accept wind from any direction without any yaw mechanism, so the average performance of this type of turbine in cluster is analyzed by changing the flow (α = 0°, 45° and 90°) of the wind turbine cluster. It is observed from this study that the average power coefficient of the cluster of turbine at the flow angle of 45° has better performance than the other pattern. Moreover, its average power coefficient is 2.3 times higher than the isolated vertical axis wind turbine. These results of the cluster simulation are used to develop an efficient wind tree to harness the low rated wind energy.

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The virus causing COVID‐19 has constantly been mutating into new variants. Some of them are more transmissive and resistant to antibiotics. The current research article aims to examine the airborne transmission of the virus expelled by coughing action in a typical intensive care unit. Both single and sequential coughing actions have been considered to get closer to practical scenarios. The objective is to assess the effectiveness of air change per hour (ACH) on the risk of infection to a healthcare person and how the air change rate influences the dispersion of droplets. Such a study is seldom reported and has significant relevance. A total of four cases were analyzed, of which two were of sequential cough. When the ACH is changed from 6 to 12, the average particle residence time is reduced by ∼7 s. It is found that the risk of infection in the case of sequential cough will be relatively low compared to a single cough if the outlet of the indoor environment is placed above the patient's head. This arrangement also eliminates the requirement of higher ACH, which has significance from an energy conservation perspective.