## 2 Related Work  
There are multiple studies on natural ventilation, including theoretical, analytical, and experimental approaches, and using computational fluid dynamics (CFD). The CFD method represents a computer simulation method that can analyze air flows using numerical analysis and data structures. CFD simulation accounts for about 70% of the scientific research on natural ventilation [5]. CFD analysis is fast and relatively low-cost compared to other methods, but the results are less accurate. Comparative studies of different methods describe this method as having a high level of accuracy [6; 7] and being suitable for scientific model experiments. In recent decades, this has been achieved by developing more accurate turbulence models, increasing the power of computer hardware, and producing guidelines for best practice [8; 9]. One of the aspects of CFD simulation represents the quality of 3D models of urban environments. The studies in a number of cases simplify the urban block geometry to cubical form [10; 11; 12; 13]. These studies are mostly conducted to obtain results that are general in nature in order to observe the influence of external conditions on the temperature, pressure, turbulence, or velocity in a generic urban environment. Simulations on real-life urban blocks [14; 15; 16], in contrast, are used in order to study urban environments in detail. It is necessary to test scenarios with different wind directions for natural ventilation analysis. [PERSON] et al. [17] experimented with the airflow from four clustered directions. The building in this study was an open-terrain greenhouse, and the researchers found a significant effect of the wind direction on the flow patterns inside the house. [PERSON] et al. [18] performed CFD simulation in similar conditions in an open field. They studied various situations by changing the wind direction from 0 to 90 degrees in intervals of 10 degrees. The results show a correlation between the air exchange rate from the outdoor to the indoor space and the wind direction. [PERSON] and [PERSON] [19] studied natural ventilation using CFD simulation with a model of a simple cubic building. Four different wind directions were studied, and they concluded that wind direction has a high impact on the natural ventilation rate. All three examples used only one building for the experiment. [PERSON] et al. [15] performed CFD simulations on a stadium building with and without surrounding buildings. The eight wind directions, represented as all cardinal and ordinal directions, were used as boundary conditions with one velocity. The study showed that surrounding structures can influence the airflow results by up to 96% and concluded that natural ventilation performance should be studied in a larger urban area. This study also showed that 2 wind directions can have a difference in airflow up to 152%, so the choice of directions inside the wind tunnel has a high impact on the final results. Research by [PERSON] [20] also included surrounding buildings in the CFD simulation. [PERSON] concluded that wind pressure distributions and ventilative heat losses were influenced considerably if more than one building was included in the research. [PERSON] et al. [21], in their review paper, stated that very little data exist on urban surroundings and the related sheltering effect. This observation was further supported by [PERSON] et al. [15], who stated that detailed studies on the effect of the wind direction and surrounding buildings on indoor natural ventilation in an urban environment are not commonly performed. In studies of natural ventilation, there are two main approaches in regard to indoor and outdoor air simulations. The coupled outdoor and indoor air flows are mixed in CFD simulations. There are multiple studies using this approach [10; 15; 22]. The decoupled approach observes indoor and outdoor spaces separately and performs simulations on different geometries. This approach has an advantage for larger systems where the potential of natural ventilation is calculated.