Composite wing trans-medium aircraft integrate the high-speed cruise efficiency of fixed-wing aircraft with the vertical take-off and landing (VTOL) flexibility of rotary-wing aircraft, boasting significant application potential in marine environmental monitoring and other fields. This paper designs a trans-medium variable tiltrotor aircraft configuration, which adopts a foldable main wing to achieve adaptive adjustment of the aerodynamic profile, equips a rear tiltrotor to satisfy both VTOL and cruise propulsion requirements, and incorporates a T- tail layout to avoid rotor downwash interference. Concurrently, a worm-gear-driven wing morphing mechanism and a servo-driven rotor tilting mechanism are developed to realize reliable multi-mode switching. Computational fluid dynamics (CFD) numerical simulations are performed using ANSYS Fluent software, and a comparative analysis is conducted on the aerodynamic characteristics and flow field features of the two modes at varying speeds and angles of attack.
Simulation and test results demonstrate that the lift-drag ratio peaks at an angle of attack of approximately 10° under cruise conditions, exhibiting excellent cruise efficiency. Flow field visualization results indicate that the flow field adheres well to the aircraft main body, and the flow field transition at the fusion zone between the T-tail and fuselage is smooth, which effectively reduces local eddy current interference. Within the high-efficiency angle of attack range, the overall aircraft flow field is uniformly distributed and the evolution of vortex structures is controllable, presenting favorable flow field stability. Additionally, the study reveals that flow separation and vortex structures in the wing-fuselage transition zone are the key factors affecting the stability of the overall aircraft flow field.