## 3 Results
### Flat-roof Building
#### 3.1.3 Turbulence Intensity and Flow Acceleration  
Figure 8 gives further insight on the turbulence intensity in the stream-wise (\(I_{U}\)) and vertical (\(I_{W}\)) directions above all measuring points for the four wind angles. Along with local wind profiles, the inflow turbulence intensity at the same height is also shown as a reference (taken from Figure 3), using a black-filled circle mark. At 0\({}^{\circ}\), the stream-wise turbulence intensity for all measurement points in the vicinity of the roof is \(>\)30%, indicating the presence of a large separation bubble. This is followed by turbulence intensities of \(\sim\)20-25% in the vertical direction. At z/D = 0.3, the turbulence intensity in the stream-wise direction is still higher than the reference profile value, within the limits 15-21%. This is not the case for upstream points (18, 20 and 22), where values are comparable to the reference ones. Turbulence intensities in the vertical direction are comparable to the reference profile within the range 10-13%. Measurements above the height of z/D = 0.3 are closer to the free-stream values, suggesting that the height of the separation region is slightly above 0.3\(D\). Similarly, to the previous case, turbulence intensity profiles at 15\({}^{\circ}\) show high turbulence close to the roof. Values at z/D = 0.075 are mostly over 30% for \(I_{U}\) and over 20% for \(I_{W}\), followed by a reduction in turbulence with increasing height. At z/D = 0.3, turbulence intensity lies in the ranges of 12-22% and \(\sim\)10-15% for the stream-wise and vertical directions, respectively. Moreover, Figure 8 reveals that values above the alignment z/D = 0.2 and z/D = 0.5 show a slight shift in turbulence intensities compared to 0\({}^{\circ}\) for both the stream-wise and vertical directions. In contrast, an increase in turbulence intensity is noticeable above the alignment z/D = 0.8. This suggests that the separation bubble moves to the right while maintaining the height of \(\sim\)0.3\(D\). Considering the 30\({}^{\circ}\) wind angle case, most of the points in the vicinity of the roof, at z/D = 0.075, show \(I_{U}>\) 30% and \(I_{W}>\) 15%. Exceptions are points above the main diagonal over the roof (36 and 54) with lower values, \(\sim\)23% for \(I_{U}\) and \(\sim\)13% for \(I_{W}\). It leads to the conclusion that these points are near the border of the cone vortex formed at the upstream edge. Measurements from height z/D = 0.3 are analogous to the reference profile values. For a wind angle of 45\({}^{\circ}\), higher values of turbulence intensities, reaching up to 50% in stream-wise and 25% in the vertical direction, are observed at the lowest measured heights, in regions affected by the two separation cones. Turbulence levels are increasing as the cone is increasing in size (e.g., above points 20 and 22). Above the main diagonal on the roof (points 18, 36 and 54), measurements at all heights are characterised by relatively low turbulence intensities. These turbulence levels are comparable or even lower, as in the case of vertical turbulence, than the reference inflow. Namely, the wind separates from the two upstream sides of the building, forming two cone vortices, while the flow at the centre of the  
Figure 7: Mean (\(C_{p\ mean}\)) and standard deviation (\(C_{p\ RMS}\)) distributions of the surface pressure coefficient for different wind angles, 0\({}^{\circ}\), 15\({}^{\circ}\), 30\({}^{\circ}\) and 45\({}^{\circ}\), along different alignments on the roof: (a) _x/D_ = 0.35, (b) _x/D_ = 0.8.  
roof might be fully attached. Again, as at 30\({}^{\circ}\), turbulence intensities from height z/D = 0.3 for all points match free-stream values. Thus, it can be concluded that for wind angles of 30\({}^{\circ}\) and 45\({}^{\circ}\), turbulence assumes characteristics similar to the free-stream values above the height z/D = 0.3 at all positions on the roof.