## 3 Results and Discussion  
### Flow Fields and Droplet Dispersion  
Figure 7 illustrates a comparison of the indoor airflow fields in the room without curtains and in the room with different curtain-hanging scenarios in the cross-section at the center point of the infected person's mouth (Y = 3 m and \(Z\) = 1.1 m), where significant differences in the distribution of the indoor airflow fields can be observed for the different measures. These differences arose from the coupling of multiple fields. First, the specific microenvironmental field around the human body, which is due to the temperature difference of the airflow around the human body, formed an upward \"thermal plume\" phenomenon, and its speed range was approximately 0.3-0.4 m/s. Second, following the convergence of the airflow originating from the bilateral air supply ports, its speed falls within the range of 0.65 to 0.82 m/s, and the existence of these converging airflows reduced the interaction of respiratory airflows between AB and BB. It is worth noting that part of the air supply disrupted the flow direction of the thermal plume, resulting in an uneven distribution of velocity and pressure in the space. This uneven distribution further drove the mixing and spreading of the airflow, creating a pronounced vortex that is mainly concentrated above the head of the passenger AB. Around passengers CB and BB, the airflow ascends along their bodies, forming a kind of indented airflow shape. These airflows eventually converged with the airflows above the space and moved towards the air vents, the location of which determined the direction of the main airflows. The exhaled airflow of an infected person flows mainly in a forward direction under the influence of the three factors of air supply, respiration, body heat plume, and exhaust air. However, the fast main airflow was obstructed by the slow airflow in the region in front of the side of the infected person, thus creating a rotating vortex (Figure 7a). The mechanism of change in the indoor airflow field caused by the four designed curtain placement scenarios will be discussed in the following sections. Figure 7b shows the airflow field for hanging curtain scheme A, where the fluid above the surface of the curtain is blocked to change the flow direction, resulting in the flow field separating to form two relatively independent regions in front of and behind the curtain. The finite flow channel formed between the two passengers on the same side of the air supply stream triggered local acceleration of the flow, so the vortex collected above BB and CB. Figure 7c,d show the flow fields of scheme B and scheme C, respectively. The airflow in the intercepted XZ plane was the same principle as scheme A, which is not discussed here. The placement of vertical curtains and the increase in the number of curtains played a decisive role in the change in flow direction in the horizontal plane under different placement schemes. Scheme B made the lounge space symmetrical from front to back, so the airflow formed a more pronounced diversion in the median line. The increase in the number of curtains resulted in a more complex vortex effect as well as turbulence enhancement effects and blocked the airflow circulation between the left and right-side passengers. Depending on the length and placement of the curtains, the airflow was cut into different zones, and the flow of airflow in each zone was different. By controlling these parameters, fine control of airflow zoning could be realized, thus achieving the purpose of improving indoor air quality. The human body's microenvironment makes it difficult to expel virus-carrying droplets at high concentrations through the dilution effect of fresh air from the ventilation system [42]. The heat generated by the human body is transferred to the surrounding air through thermal radiation and convection, causing an increase in the temperature of the air around the body, resulting in the phenomenon of thermal plumes.