# Research on the Aerodynamic-Propulsion Coupling Characteristics of a Distributed Propulsion System
## 5 Conclusions  
In this study, a circumferential body force model based on local flow parameters was developed and validated. An over-wing symmetric configuration with five distributed  
Figure 21: Swirl distortion at ducted fan inlet: (**a**) distribution of swirl angle; (**b**) swirl distortion index \(DC_{60}\).  
ducted fans was constructed, and the impacts of the flight Mach number on the aerodynamic performance and flow field structure of the coupled configuration were investigated in detail. For the integrated configuration considered in this study, the main conclusions can be drawn as follows:  
1. The higher the flight Mach number is, the greater the lift obtained by the wing is. When the Mach number is 0.5, the maximum lift coefficient of the wing increases by 306% compared with that at a Mach number of 0.2. However, the stall angle of attack of the wing during flight decreases as the flight Mach number increases. Under flight Mach numbers ranging from 0.2 to 0.5, the corresponding stall angles of attack are 38\({}^{\circ}\), 32\({}^{\circ}\), 26\({}^{\circ}\), and 23\({}^{\circ}\), respectively. The stall angle of attack at a Mach number of 0.5 decreases by 15\({}^{\circ}\) compared with that at a Mach number of 0.2.
2. Fans #1 and #5 have the strongest ability to resist airflow separation, while fan #3 has the weakest ability. When the angle of attack is 26\({}^{\circ}\), the mass flow rate and thrust of fans #1 and #5 increase with the increase in the flight Mach number. However, when the Mach number is 0.4, the mass flow rate and thrust of fan #3 decrease significantly. Compared with those at a Mach number of 0.2, the mass flow rate and thrust of fan #3 decrease by 16% and 28%, respectively.
3. The higher the flight Mach number is, the greater the degree of intake distortion of the ducted fans is. For total pressure distortion, as the Mach number increases, fan #3 is the most affected by total pressure distortion, followed by fans #2 and #4, and fans #1 and #5 are the least affected by total pressure distortion. For swirl distortion, as the Mach number increases, fans #1 and #5 are the most affected by swirl distortion, followed by fans #2 and #4, and fan #3 is the least affected by swirl distortion.
4. For the configuration studied in this paper, the fan located in the middle of the ducted fan array is most sensitive to changes in the angle of attack and the incoming flow velocity. At large angles of attack or high incoming velocities, the performance of the middle fan is significantly reduced. However, the edge fans are less affected by the incoming flow and exhibit a relatively stable aerodynamic performance.  
Conceptualization, methodology, resources, and supervision, X.Y.; software, validation, formal analysis, writing--original draft preparation, T.L.; investigation, data curation, writing--review and editing, W.J. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Key R&D Program of China (2022 YFB4301000). Not applicable. Not applicable. Not applicable. Data Availability Statement: The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author. The authors declare no conflicts of interest.