Aerodynamic modeling and VTOL/Hover dynamics analysis of a small-scale all-wing tail-sitter solar-powered UAV with double layer distributed electric propulsion

To address the dependency on runways and the limited solar cell coverage inherent in conventional solar-powered Unmanned Aerial Vehicles (UAVs), this paper proposes a novel Small-Scale Double-Layer Distributed Electric Propulsion All-wing Tail-Sitter Solar-Powered (DDEP-ATS) UAV. This configuration eliminates aerodynamic control surfaces and employs differential thrust for attitude control, thereby enhancing photovoltaic efficiency and flight flexibility. A comprehensive aerodynamic model is established that explicitly accounts for slipstream tube contraction-expansion effects and the longitudinal spatial distribution of propellers. Through integrated propulsion bench tests and CFD simulations, the study reveals for the first time a nonlinear lift‑enhancement mechanism (up to 1.84 times) induced by longitudinal slipstream coupling between the upper and lower propeller layers. Compared with the spanwise single‑layer configuration, the proposed layout achieves approximately 20% higher lift and only 13% of the drag, demonstrating aerodynamic superiority of the longitudinal distributed propulsion concept. The resulting aerodynamic model is integrated into the full aircraft dynamic formulation to evaluate its influence on VTOL performance, hovering stability, and transition feasibility. Results reveal that this configuration possesses an inherent dynamic tendency for a natural transition to fixed-wing mode. This study not only uncovers the lift enhancement mechanism of longitudinally distributed propulsion but also provides a critical theoretical foundation and modeling support for the design and control of next-generation VTOL solar aircraft.