# Wind Field Characteristics of Complex Terrain Based on Experimental and Numerical Investigation
## 5 Wind Tunnel Test Results
### Mean Velocity  
The profile of the flow velocity U is normalized by the average velocity U\({}_{\rm r}\) of the inflow. Figure 12 shows the normalized wind speed profile of each measuring point under different inflows and gives the corresponding wind profile coefficients. It can be seen from the figure that the wind profile coefficient shows great discreteness, which is quite different from the recommended value of 0.12 in the specification. It shows that the shape of the wind profile in different areas is different. Among them, the wind profile coefficient of each measuring point under 90 \({}^{\circ}\) inflow is the closest to the standard value. As shown in Figure 12a, the wind speed at P2 under 40\({}^{\circ}\) inflow is the largest, which is mainly because there are no mountains or small islands in front of P2. In the process of climbing along the hillside where P2 is located, the wind speed increases and the wind profile develops well. In contrast, other measuring points have low wind speed due to the shielding of mountains of different sizes. Although P5 is situated on the leeward slope, the wind speed is low only at the lowest point of the ground due to the high altitude. For flat areas, the inflow reaches P1 after passing through the whole terrain, so the wind speed at P1 is generally low. The inflow develops well after the recovery over lower terrain before reaching P3, so the wind  
Figure 11: Velocity results of numerical simulation and wind tunnel test. (**a**) 40\({}^{\circ}\) (**b**) 90\({}^{\circ}\) (**c**) 270\({}^{\circ}\).  
speed is different from P1. P4 in the valley is located at the lowest part of the downhill of the air flow, where the air flow is greatly disturbed, resulting in a low wind speed below 200 m. But after 200 m, the speed also increases gradually.  
As shown in Figure 11(b), each measuring point forms a better wind profile under the 90\({}^{\circ}\) inflow. The wind speeds of P2 and P3 are the highest, which have a great connection with the clear space ahead of them. The wind profiles of P1, P4 and P5 are relatively close, and the inflow is disturbed before reaching the three measuring points from 90\({}^{\circ}\). It is worth noting that the wind speed of P4 is large at 400 m, but the wind speed changes little after that. This may be due to the acceleration effect of the valley; the wind speed near the ground increases more than that at high altitude.  
The wind profile of P3 in Figure 11(c) is irregular. This is mainly because P3 is in the nearest place to be covered by mountains under the inflow. There is also a barrier in front of P2 but the wind speed is high. The reason is that the change in terrain elevation is relatively stable after crossing the barrier. Moreover, it can be seen that the wind speed of P2 below 200 m also changes greatly, which is affected by blocking. The wind speed of P5 is the largest among all the measuring points. From the terrain analysis, P5 is on the windward slope with large elevation, and the air flow has been fully accelerated. The wind profiles of P1 and P4 are close, and the wind speed is at a medium level.  
For the wind speed, the local topographic characteristics and the incoming wind direction play a joint role. The wind speed at the same measuring point varies greatly under different inflows, and the wind speed at different measuring points is also greatly different under the same inflow. This needs to be deeply analyzed in combination with the terrain. Combined with the above analysis, the wind speed on the windward slope is often  
Figure 12: Profiles of mean velocity at measurement locations. (**a**) 40\({}^{\circ}\) (**b**) 90\({}^{\circ}\) (**c**) 270\({}^{\circ}\).  
large. For valleys or relatively flat areas, it is necessary to deeply explore the change in wind speed according to the surrounding terrain.