## 4 Results and Discussion
### Performance of Improved Design  
The improved models are analyzed and compared with the original model, the incoming flow condition is uniform flow, and the wind speed is 6.7 m/s. Considering that both Model 1 and Model 2 are symmetric models, only a range of 0-45\({}^{\circ}\) is needed to simulate them. The average speed ratio of Model 0, Model 1 and Model 2 with different wind directions is shown in Figure 12. As previously analyzed, since the outlet plane of Model 1 is parallel to the incoming flow, the average speed ratio of Model 1 is basically the same as that of Model 0 when \(\theta=90^{\circ}\). Figure 13 shows the streamlines of the Venturi tube when \(\theta=90^{\circ}\) in Model 0 and \(0^{\circ}\) in Model 1. At this point, the positions of the baffles at the inlet of the system and the exits relative to the airflow in the two models are the same. The streamlines are almost identical in both cases at the Invelox system exit and in the Venturi tube, so the average SR of the two cases are basically the same.  
Model 1 greatly improves the performance of the Invelox system when \(\theta\) is greater than \(90^{\circ}\), because the system exit never faces the incoming flow. However, although the overall performance of the system has improved, Model 1 is not as good as Model 0 in the case of small included angles, and this has led to Model 2. Because the outlet normal direction of Model 1 is always perpendicular to the incoming flow, no matter how the wind direction changes, the external air flow will always  
Figure 11: The total pressure contours in the symmetric plane of original Invelox system; (**a**) \(\theta=0^{\circ}\) and (**b**) \(\theta=180^{\circ}\).  
Figure 10: Velocity vector at the exit of the original Invelox model under different incoming wind directions; (**a**) \(\theta=0^{\circ}\), (**b**) \(\theta=30^{\circ}\), (**c**) \(\theta=60^{\circ}\), (**d**) \(\theta=90^{\circ}\), (**e**) \(\theta=120^{\circ}\), (**f**) \(\theta=150^{\circ}\) and (**g**) \(\theta=180^{\circ}\).  
form an airflow cover at the exit of the system, blocking the flow of internal air, thus reducing the aerodynamic performance of the system. Thanks to the protection of the windshield for airflow at the exit, the performance of Model 2 is significantly better than that of the Model 1. Figures 14 and 15 show the comparisons of the flow field without and with the windshield.  
As can be seen from Figures 14 and 15, the windshield plays a good role in protecting the airflow at the outlet of the system from the interference of the airflow from the external environment. Due to the existence of the windshield, there is a flow separation vortex inside the windshield. Under the guidance of the vortex, the external airflow changes from the original horizontal movement to vertical movement, with the same movement direction as the internal airflow. The airflow from the Venturi can be mixed with the airflow inside the windshield under the protection of the windshield and then discharged into the atmosphere. At this point, the effect of the external flow on the internal flow is no longer an obstacle, but a gain. The average speed ratio increased from 1.50 to 2.13, that is an increase of about 42%. If only the range of 0-90\({}^{\circ}\) is considered, the improvement of Model 2 is about 19.2% compared with Model 0.