## 5 Conclusions  
In the present study, the instantaneous and average aerodynamic forces of a VAWT with inclined pitch axes were simulated by an actuator line model. The effect of two pitch parameters, namely the fold angle and the incline angle, was illustrated, and major findings followed.  
The fold angle changed the angles of attack directly and, in turn, the aerodynamic forces. Blade folding movement in the positive direction made the variations of the \(C_{Fx}\) flatter and strengthened the instantaneous lateral forces away from the main shaft. Furthermore, the fold angle intensified the fluctuations of the \(C_{Fz}\). As for overall performance, the \(C_{P}\) of the VAWT varied with different fold angles. The \(C_{Thrust}\) grew when the blades were folded in the positive direction, but the \(C_{Vertical}\) increased when the blades were folded in both directions. The direction of the average lateral force depended on the fold angle.  
Diverse sensitivities of the power control could be obtained with different incline angles, since the sensitivity of the \(C_{P}\) to the fold angle diminished with incline angles away from \(90^{\circ}\). A similar effect could be found for the \(C_{Thrust}\) and \(C_{Lateral}\). Opposite directions of the \(C_{Vertical}\) were seen for incline angles higher and lower than \(90^{\circ}\). The upward vertical forces could diminish the burden of the gravity of the blades on the supporting structures of the wind turbine. From studies along the blade span, it is clear that incline angles away from \(90^{\circ}\) led to an asymmetric distribution of the aerodynamic forces about the equator. For the \(C_{Thrust}\), the tilting moments applied to the main shaft and the tower of the wind turbine were different with various incline angles. Specifically, a \(2.3\%\) reduction of the tilting moment to the main shaft at \(z/H=-0.5\) with \(\gamma~{}=~{}150^{\circ}\) was estimated, compared with that utilizing \(\gamma~{}=~{}90^{\circ}\). Variations of the \(C_{Lateral}\) and \(C_{Vertical}\) were minor.  
The present study lays a necessary foundation for dynamic pitch and adaptive passive pitch regulation of a VAWT with inclined pitch axes. Aerodynamic performance under a low tip-speed ratio with the occurrence of a deep stalk is good to explore as a comparison and supplement to the present study. In addition, the effect of the asymmetric distribution of aerodynamic forces on the structural performance of the wind turbine under the conditions of various incline angles also needs to be investigated in detail in the future.  
Conceptualization, J.G.; formal analysis, J.G.; writing--original draft preparation, J.G.; writing--review and editing, T.Q. and L.L.; supervision, T.Q. and L.L. All authors have read and agreed to the published version of the manuscript.  
Figure 11: Average aerodynamic forces along the blade span with different incline angles: (**a**) \(C_{H}\), (**b**) \(C_{Thrust}\), (**c**) \(C_{Lateral}\) and (**d**) \(C_{Vertical}\).  
**Funding:** This research was funded by the National Natural Science Foundation of China (No. 51875305).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.  
**Conflicts of Interest:** The authors declare no conflict of interest.