## 2 Research Methods
### CFD Simulations  
This study utilized the software VENT 2024 to model the performance of four scenarios regarding outdoor wind conditions and internal ventilation throughout winter and summer. VENT passed the software evaluation of the Ministry of Housing and Urban-Rural Development of China in 2017, and many studies have proved its accuracy [44]. Furthermore, VENT can utilize the \"Special Meteorological Dataset for Thermal Environment Analysis of Chinese Buildings\" to extract the prevailing wind directions and average wind speeds for the winter and summer seasons at the project location. When presenting the analysis results, VENT is capable of directly comparing them with relevant evaluation standards in China, thereby directly yielding analytical conclusions and enhancing work efficiency. The predominant wind directions for Xi'an throughout the year and for individual months are presented in Table 4 below. The annual predominant wind direction in Xi'an  
Figure 5: Floor plans for each scenario. is northeasterly, characterized by a relatively high frequency of winds blowing from this direction. Additionally, the northeasterly wind also dominates as the most frequent wind direction in each season. Notably, the annual average calm wind frequency is 35%. The city experiences an annual average wind speed of 1.8 m/s, whereas the average wind speed of the predominant northeasterly direction is 2.5 m/s. Therefore, 2.5 m/s and ENE were chosen for the CFD simulations. The \"Green Campus Evaluation Standard\" (GB/T51356-2019) [2] recommends setting the dimensions of the simulation domain for the incoming wind direction and wake direction at 4 and 6 times the height of the model, respectively. The lateral boundary dimension should be set at 2 times the height of the model. The height of the computational domain is typically three times the height of the model. The simulation area should encompass buildings located within a 500 m radius to accurately represent their influence on the chosen teaching buildings. VENT automatically divides the model into grids. The software offers three types of grids, including regular grids, ground grids, and boundary layer grids. Regular grids refer to grids other than those near the ground and buildings, which do not require special densification. The area close to the building is called the near field, while the area far away from the building is called the far field. In the near field, the ground grid needs to be densified, corresponding to a larger subdivision level, whereas in the far field, the ground grid is relatively sparse, with a smaller subdivision level. The boundary layer grid is the grid that is significantly close to the surfaces of the ground and buildings. Because of the inherent viscosity of air, it experiences resistance from the ground or building surfaces. The airflow velocity near the ground or building walls is almost zero, and the velocity increases with the distance from the ground or building surfaces. This results in a gradient distribution of flow velocity within a certain thickness of an air layer near the ground, eventually reaching the mainstream velocity. This layer of air is commonly referred to as the boundary layer or attached layer. In computational fluid dynamics analysis, to capture the airflow characteristics within the boundary layer or attached layer and improve analysis accuracy, it is advisable to layer the grids in this region, forming boundary layer grids. Furthermore, VENT provides three distinct levels of simulation accuracy, specifically Level 1 through Level 3, each of which corresponds to varying mesh densities. Typically, Level 1 serves as an initial assessment of the simulation, encompassing aspects such as computational time and result accuracy. Conversely, Level 2 and Level 3 offer increased simulation precision, albeit at the cost of longer computational durations.