## 3 Results and Discussion
### Computational Simulation
As result, the vortex of the airflow promoted the worst conditions of air circulation. A strong vortex is developed at the top of the ridge structure when the wind direction occurred along the length of the CBP. The vortex occupies almost the whole cavity in the ridge structure due to the inversed flow created through the central surface bedding area. The building geometry is a crucial aspect to achieve efficient natural ventilation and indoor thermal comfort in a CBP environment. Vortex paths are important, especially in the surface of compost bedding where turbulent fluctuations dominate over the mean flow [25]. Measurements in a full-scale set-up of this kind are challenging, not the least due to the variation of wind direction during averaging periods. Figure 9 shows the simulated air velocity vectors vertically inside and around of CBP barns equipped with open ridge (OPR) using different wind directions. According to Figure 9A,B, these barns produced higher ridge vent flows for the south to north and north to south wind directions at wind velocities above 0.07 m s\({}^{-1}\). Wind direction comparisons indicated that south winds consistently produced the highest ridge vent flows (Figure 8A), while the east and west winds generated the lowest ridge vent flows (Figure 9C). It can be seen that the main flow tended to turn opposite the main wind direction. In all cases, the roof presents a complicated area to model due to turbulent shear layers and ridge vent openings zones. However, this is likely to be the least important face for ventilation calculation in most animal facilities. A similar effect was observed by other researchers [23]. Figure 10 shows the simulated results of CBP barn equipped with open ridge with chimney (ORC) in different wind directions. Figure 10A,B shows considerable variation in the direction of the air velocity vectors, and consequently the flow is far from being two-dimensional. Near the  
Figure 8: Air velocity vectors obtained in the CFD simulation of the CBP barn equipped with closed ridge (CLR) and using three wind directions—WDs: (**A**) south to north, (**B**) north to south and (**C**) east to west. Figure 9: Air velocity vectors obtained in the CFD simulation of the CBP barn equipped with open ridge (OPR) and using three wind directions—WDs: (**A**) south to north, (**B**) north to south and (**C**) east to west. ridge opening, it can be seen that vortex was located above the roof in the right (Figure 10A) and left (Figure 10B) side. From the Figure 10B, the north wind direction, which produced the highest ridge vent flows, also generated high air velocities inside the structure. The contour plot of wind speed revealed periodic air recirculation zone above the building due to the flow redirection caused by the chimney. Due to a portion of the high-speed, incoming airflow becomes incorporated in the indoor flow regime. This airflow recirculation was highly influenced by the velocity of the short-circuiting flow beneath the roof. Distribution of air velocity on the compost area in winds direction east to west (Figure 10C) was more uniform than the other directions tested. In this case, the air movement tended to stabilize, generating lower air velocity above the compost area. The amount of obstruction of the building is known to have an impact on the flow that crosses the structure, whereby potentially affecting air velocity values [15]. Due to the size of the heat source and the geometric of the building, the flow was forced over the ridge vent. The flow near the floor was decelerated due to the stagnation point at the fence and wall that directed the airflow to the top of the building. Figure 11 shows the simulated results of CBP barn equipped with elevated ridge (ELR) in different wind directions. The east and west wind directions present the higher ridge vent outlet flow (Figure 11C). The wind flows up the windward wall surface and above the roof of the barns with east and west winds (Figure 11C) but hits the roof inside the barn with south and north winds (Figure 11A,B).