## 4 Results and Discussion
### Incoming Velocity Considering Atmospheric Boundary Layer  
As mentioned above, wind power systems eventually need to be placed in the atmosphere to make sense. There is almost no uniform wind in the atmosphere, so it is of practical significance to consider the atmospheric boundary layer. A total of three wind profiles were considered, and the wind profile indexes were 0.1, 0.2 and 0.3, respectively. Different wind profile indexes represent different geomorphic features, small values represent flat suburban areas, and large values represent densely urban areas. The entry heights of Model 1 and Model 2 are consistent with Model 0. Since the distribution of wind velocity along the height is non-uniform after considering the atmospheric boundary layer, the incoming wind velocity in the SR definition is set as the wind velocity at the height of the center of the Invelox system entry. Figure 16 shows the variation of the speed ratio of Model 0, Model 1 and Model 2 to the wind direction under different incoming wind profiles. With the increase of the wind profile index, the aerodynamic performance of the original Invelox model and its improved configuration decreased to different degrees. The stronger the performance, the greater the degradation. This is mainly due to the different environmental wind velocity near the system exit. Under different working conditions, the average incoming wind velocities at the inlet of the system are similar, but the environmental wind velocities at the exit are greatly different, as shown in Figure 17.  
Figure 14: Comparison of velocity distribution in vertical plane; (**a**) Model 1 and (**b**) Model 2. Figure 15: Comparison of vectors near the Invelox system exit; (**a**) Model 1 and (**b**) Model 2. For Model 0, when \(\theta\) is equal to \(0^{\circ}\), the external air has less interference with the flow from the Venturi tube. With the increase of \(\theta\), the external air flow is accelerated due to the expansion of the system outlet, and has a certain suction effect on the internal air flow. When \(\theta\) reaches \(90^{\circ}\), the gain effect of the external flow disappears and is replaced by the blocking effect. The external air instead forms a wall of air to prevent the internal air flow from flowing out, so that the speed ratio of the system drops significantly. When \(\theta\) exceeds \(120^{\circ}\), the initial counterflow occurs in the Venturi tube, so the stronger the external flow near the outlet, the more obvious the counterflow. Under the condition of uniform inflow, the wind speed at the outlet height of the system is 6.7 m/s, and when the wind profile index is equal to 0.1, 0.2 and 0.3, the corresponding wind speed at the outlet height of the system is 6.2, 5.7 and 5.2 m/s, respectively. Therefore, when considering the effect of the atmospheric boundary layer, the speed ratio of the system is smaller than that of the uniform inflow. With the increase in the  
Figure 16: The comparison of speed ratios of different models under different wind directions with different wind profile indexes. Figure 17: Distribution of incoming wind velocity corresponding to different wind profile indexes. wind profile index, the performance will be further weakened. When the wind profile index is equal to 0.1, 0.2 and 0.3, the speed ratio decreases by an average of 7.07, 9.14 and 10.73% compared with the uniform inflow if the angle is only considered within the range of 0 to 90\({}^{\circ}\). For Model 1, because its flow field characteristics are similar to that of Model 0 when 0 is equal to 90\({}^{\circ}\), the aerodynamic performance variation characteristics of Model 1 under different wind profiles are similar to that of Model 0 when 0 is 90\({}^{\circ}\). It can be seen from the figure that the speed ratio of Model 1 is less affected by the incoming wind distribution. The average speed ratio decreases by 6.74, 5.85 and 5.05% compared with the uniform inflow.