## 2 Materials and Methods
### Model Validation and Mesh Independence Test  
In order to verify the accuracy of the present numerical model in predicting the transport process of exhaled droplets from an infected person, a two-region room with dimensions of 5 m \(\times\) 2.4 m \(\times\) 3 m was established with reference to the experimental conditions of [PERSON] et al. [40]. The two regions were of the same size, and the air could be circulated inside the two regions. In the initial state, the oil particles were uniformly  
Figure 3: Four separation schemes for curtains.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Boundary** & **Momentum** & **Thermal** & **DPM** \\ \hline Door & No-slip & 26 \({}^{\circ}\)C & Reflect [38] \\ Walls & No-slip & 26 \({}^{\circ}\)C & Reflect \\ Table & No-slip & Adiabatic & Reflect \\ Bodies & No-slip & 31 \({}^{\circ}\)C [39] & Trap \\ Curtain & No-slip & Adiabatic & Reflect \\ Outlet & Pressure outlet & / & Escape \\ Inlet & 1.63 m/s & 20 \({}^{\circ}\)C & Escape \\ Mouth (susceptible person) & \(-\)0.37 m/s & 26 \({}^{\circ}\)C & Escape \\ Mouth (infected person) & 0.37 m/s & 33 \({}^{\circ}\)C [39] & Escape \\ \hline \hline \end{tabular}
\end{table}
Table 3: Boundary conditions.  
distributed in region 1 with a density of 865 kg/m\({}^{3}\) and a particle size range of 1-5 \(\upmu\)m and were influenced by fresh air (air change rate of 9.216 h\({}^{-1}\) per hour), released in region 2. Comparing the simulation results with the experimental measurements, the particle concentrations are shown in Figure 4. As the boundary conditions of the simulation cannot be completely restored to the actual boundary conditions, by comparing the experimental results with the simulation results, it can be seen that the two values cannot be exactly the same but have the same trend and a correct match.  
In addition to the above verification, a ventilation test was carried out in a laboratory, in which a table was placed in the room, and the room dimensions were 3.78 m \(\times\) 4.78 m \(\times\) 2.86 m. Four test trees with 24 measuring points were arranged in the room to measure the indoor air temperature. The boundary conditions of the model were set according to the experimental data as much as possible. The temperature of the walls was set to 7 \({}^{\circ}\)C, and the heat transfer coefficient was set to 0.81 W/(m\({}^{2}\cdot\)K), respectively. The air supply temperature was 20 \({}^{\circ}\)C, and the velocity was 2 m/s. Figure 5 demonstrates the test flow, laboratory model, and a comparison of the simulated data in this paper with the simulated data and experimental data regarding and temperature of the airflow. Individual points were found to be inaccurate. This may be due to the assumption that the heat transfer characteristics remain constant at any point on an isothermal wall surface, which is not realistic. Nevertheless, the overall data are in good accordance, which means that the RNG \(k\)-\(\varepsilon\) turbulence model used in this paper is appropriate.  
Figure 4: Schematic of model validation and comparison with the results of [PERSON] et al. (2018).  
Figure 5: _Cont._  
In order to eliminate the effect of mesh size on the calculation results, the mesh was coarsened and refined by increasing all mesh sizes by a factor of 2 and 0.5, respectively. Three sets of grids (2.23 million, 4.23 million, 8.65 million) were created by selecting case 1 without a curtain to perform grid independence checking. The airflow velocities at three locations on the x = 1.5 m profile were compared. As shown in Figure 6, there is a correlation between the calculation parameters and the number of nodes, and the difference between the calculation results of 4.23 million nodes and 8.65 million nodes is relatively small. Considering the calculation accuracy and the calculation time, the number of nodes was finally selected as 4.23 million.