# A Parametric Study of Wind Pressure Distribution on Facades Using Computational Fluid Dynamics
## 4 Results
### Results for Geometry No. 1 (g = 80 mm d = 400 mm)  
The average wind pressure distribution and wind flow behavior were captured for a period of three residence times, equal to 2.52 s (Figure 9). At the building's upper left corner, wind speed is accelerated by 67% percent, from 24.9 m/s to 41.5 m/s, causing flow separation over the building's length. The flow then recirculates at the rear of the building, with suction arising toward the top right corner of the building as part of maintaining a continuity of air surrounding the building. This behavior is typical of bluff bodies.  
The situation was more complex in the lower half of the structure where the building interacts with the facade. Flow separation was most obvious at the bottom edge of the leading fin (in plan-view), compared with the fins that it shelters from oncoming wind. Wind speeds increase significantly at this location, as well as between the underside of the building and the top edge of the leading fin. This junction between facade and building represents a contraction in the flow, where the increased rate of airflow is accompanied by a drop in pressure, termed the Venturi Effect, evident in Figure 9b. Over time, vortex shedding is most apparent at the top right corner of the building and the bottom edge of the leading fin.  
The critical fin was determined to be the leading fin. It is exposed to oncoming wind without the sheltering effect seen for both the inner fin and the end fin. The greater the combination of windward pressure and leeward suction, the greater the magnitude of net pressure. As a result, the critical fin undergoes the greatest stress within the facade. It also imposes the most significant bending moment with respect to its support bracket, as well as the building itself.  
Strong negative pressure at the critical fin's bottom end causes pressure to build toward the top of the fin. A smaller magnitude suction occurs at the fin's top end. Vortex shedding is apparent in both of these negative regions. The leeward face tends to have an increase in magnitude of suction with distance from the top of the fin. This implies the suction arising from maintaining the continuity of airflow on the other side of the fin, places a greater drop in pressure on the leeward face, compared to the fin's top edge where high velocity wind is squeezed across a narrow 80 mm gap. The lack of  
Figure 9: Results for Building with g = 80 mm, d = 400 mm (**a**) Time-averaged velocity (vector arrows) and pressures (contours) (**b**) Time-averaged pressures (**c**) Peak pressures (**d**) Peak and time-averaged net pressures (kPa) versus position from top of fin in meters.  
stability associated with the solution for the fin corners places greater uncertainty on the accuracy of the larger values derived at these locations.  
The contour plot for peak pressures represented in Figure 9c describes the condition where, with 95% probability, pressure and suction will not be exceeded. The analysis correlates with the event of highest windward pressure directly leading to maximum leeward suction. The peak values indicate that the time-averaged case significantly underestimates the pressures in the event of extreme loading (Figure 9d). The variability of the wind flow within the transient analysis is, therefore, addressed and highlights the difficulties that arise in turbulent fluid dynamics.  
The peak pressures acting on windward and leeward faces are of a similar profile to the time-averaged case. At the critical fin, the magnitude of pressures increases, with its overall wind load more than doubling. The lever-arm distance between the bracket and fin is similar to that calculated as part of a time-averaged analysis and is located at the approximate center of the fin in both cases.