Experimental and numerical investigation of the effect of the location of ventilation air-vent in elevators on the spread of particles containing COVID-19 and similar viruses

During the COVID-19 pandemic, the number of approximately 530 million cases and the loss of 6.3 million lives since the day it was recorded have had very negative effects on people in terms of both health and psychology. In addition to these effects, the economic order has deteriorated as many industries and factories have been closed due to restrictions. Obesity and the negative effects on mental health, especially in children and adolescents, are other important negativities. Considering these negativities, many studies conducted in recent years have determined that COVID-19-like viruses, especially in closed areas, spread more quickly through the air rather than by contact with surfaces. Therefore, what kind of practices can be used to reduce COVID-19-like contagion, how ventilation systems can be optimized and designed, and examining the mechanisms of transmission of the virus through respiratory droplets are of critical importance in terms of reducing the effects of both current and future pandemics. Today, researchers have focused on developing passive methods to prevent the spread of the virus, especially in closed areas, through the air. Elevators are the areas with the highest risk of transmission of COVID-19-like viruses, as they cannot control the distance between people and are likely to be used by people of all ages, infected or not. In studies to be conducted on this, the biggest challenge in determining optimal ventilation strategies in terms of virus spread is that it is not possible to work directly with the virus. The most practical method to overcome this difficulty today is CFD simulations with processes verified with experimental data. In this thesis, the spread of virus-containing particles in a hospital elevator, which is taken as a reference, was investigated with CFD simulations for a total of 15 situations in five scenarios for each of the three positions of the infected person. In the first stage, a prototype of the reference hospital elevator was manufactured at a ¼ scale within the framework of geometric and dynamic similarity. On the prototypes; (i) the current situation where the air outlet vents are on the ceiling (I-Scenario), (ii) the air outlet vent is on the rear surface (x/w=0, y/L=1, z/h=0.153) (II-Scenario), (iii) the air outlet vents are on the back side of the side surfaces (x/w=±0.5, y/L=0.866, z/h=0.11) (III-Scenario), (iv) the air outlet vents are in the middle side of the side surfaces (x/w=±0.5 y/L=0.5, z/h=0.11) (IV-Scenario) and (v) the air outlet vents are in the front side of the side surfaces (x/w=±0.5, y/L=0.134, z/h=0.11) (V-Scenario) air outlet vents and flow velocity measurements were performed on nine vertical axes. In the next stage, simulations were conducted under the same boundary conditions as the measurements and the CFD simulation processes were verified with the measurements. In the final stage, simulations were conducted for the 15 cases mentioned above. Open-source free software (FreeCAD, Salome, OpenFOAM etc.) were used in all simulation processes. In the studies conducted, two symmetrical vortex systems covering the flow area were observed in all scenarios. It was observed that the ventilation systems commonly used in today's elevators (I-Scenario) caused the spread of virus-containing particles throughout the entire elevator. It was determined that this negativity could be eliminated by a passive flow method in the form of changing the location of the air outlet vents. In the studies carried out within the scope of the thesis, it was determined that the best air outlet vent location in terms of spreading the virus for the infected person's y/L=0.88 and 0.5 positions was two symmetrical vents on the side surfaces at x/w=±0.5, y/L=0.866, z/h=0.11 points (III-Scenario).