In order to carry out the design of distributed electric propulsion (DEP) aircraft, it is important to understand the flow mechanism and the changing law of aerodynamic comprehensive gain of DEP aircraft under strong coupling effects of the distributed power and the wing. Aiming at distributed propeller-wing layouts, the present study investigates the aerodynamic performance of DEP configurations based on the VLM-ADT (vortex lattice method - actuator disk theory) fast solver for aerodynamic characteristics. The effects of three factors, i.e., the propeller number, the rotating direction, and the propeller spacing, on the aerodynamic performance metrics such as the lift-to-drag ratio L/D, the power load T/P, and the overall efficiency L/P, are studied in particular. As the number of propellers increases, the lift-to-drag ratio decreases, but the overall efficiency increases. When the number of propellers is not larger than 5, the lift-to-drag ratio of the co-rotating configuration is greater than that of the counter-rotating configuration. When the number of propellers is 7, the lift-to-drag ratio of the counter-rotating configuration is greater than that of the co-rotating configuration. Compared to the co-rotating configuration, the lift-to-drag ratio of the counter-rotating configuration increases when the propeller disk load is increased. The distributed propellers increase the lift and drag at the same time when they are densely concentrated at the wing tip. When the wing-tip propeller is fixed at the wing tip while the other propellers are densely concentrated near the center of the wing, it has the effect of increasing the lift and reducing the drag, and the lift increase is more than that of the propeller concentrating at the wing tip.

Propellers are widely used in distributed electric propulsion aircraft, where a significant propeller-wing aerodynamic coupling effect exists. By changing the axial induced velocity distribution to control the propeller slipstream, the propeller chord length and torsion angle distributions were obtained. An efficient propeller design method considering the slipstream effect was proposed, and the feasibility of the method was verified. The cruise and hover aerodynamic characteristics of the designed propellers in isolated and distributed configurations were calculated and compared with the minimum induced loss method. The results show that, for the same cruising lift coefficient, the efficiency of the designed propeller is 3.4%–6.6% higher than that of the minimum induced loss method. The hovering efficiency of a single propeller is 10.4%–13.5% higher than that of the minimum induced loss method at different rotational speeds. In the distributed configuration, the designed propeller’s hover efficiency is 13% higher than that of the minimum induced loss method. The designed propeller meets its design requirements in both cruise and hover states, maintaining high-efficiency operation.

Traditionally, the internal structure of aircraft wings is generally straight spars and ribs. The use of curvilinear spars and ribs (SpaRibs) can greatly broaden the design space of the aircraft wing structure and further improve the aeroelastic performance of the aircraft wing. Since the linked shape method (LSM) is not easy to automatically model, the projection mapping method was proposed to perform two space transformations to realize the automatic modelling of the SpaRibs. Based on genetic algorithm, an aeroelastic comprehensive optimization design method was proposed for aircraft wings with SpaRibs. The supersonic doublet-lattice method was used to calculate the unsteady aerodynamics, and the modal method was used for the static aeroelastic analysis. The optimal design was carried out by considering the flutter velocity and static aeroelastic deformation constraints. A comprehensive optimization design calculation example of a flying wing aircraft shows that the flutter velocity can be increased by 20.34% on the basis of a weight increase of 1.321% for a wing with a SpaRibs structure. The size parameters are further optimized on the basis of the SpaRibs configuration. Under certain constraints, the weight reduction is 21.76% compared with the initial configuration; the comprehensive (one-step) optimization of the SpaRibs configuration parameters and size parameters is combined, and the weight reduction can reach 26.44% compared with the initial configuration. The weight of the aircraft wing can be effectively reduced by combining SpaRibs design optimization and size optimization, which provides a fast and effective aeroelastic comprehensive optimization design method for the overall design of the flying wing aircraft structure.

The rudder surface effectiveness loss directly affects the gust alleviation effect of flexible aircraft, considering the rudder surface effectiveness loss is the key to the design of an active gust alleviation control system. In order to tackle the issue of gust interference in flexible aircraft, a high aspect ratio flexible aircraft model is utilized to create a structural dynamics model of the flexible aircraft that takes into account elastic modes and rigid body motion. Additionally, the rudder effectiveness loss of the rudder surface actuator is taken into consideration. An adaptive observer is designed to estimate the efficiency factor of the rudder surface actuator online in real-time, reconstruct and solve the adaptive active fault-tolerant $H_{\mathrm{\infty }}$ controller, and achieve aircraft gust load alleviation. Under discrete and continuous gust excitation, simulation of the aircraft’s open/closed loop time domain response demonstrates that both $H_{\mathrm{\infty }}$ control and proportional-integral-derivative (PID) control can achieve better alleviation effects under the rudder surface ineffective energy loss, and that $H_{\mathrm{\infty }}$ control’s response time is faster than PID control’s. Under the rudder efficiency loss, the adaptive observer can complete the efficiency factor evaluation in less than 4 seconds, and the $H_{\mathrm{\infty }}$ controller, which is designed based on this efficiency factor, can achieve gust alleviation that is comparable to the ideal scenario.