The design of unmanned combat aerial vehicles (UCAVs) is primarily governed by the low-observability requirement for military applications rather than aerodynamic performance. The conceptual design and optimization of UCAV models via size and shape variables for different missions in different flow regimes form a research area for military vehicle design. Flying wing UCAVs experience flow separation during takeoff and landing, and furthermore exhibit stability issues. The aerodynamic performance of these UCAVs can be significantly improved by redesigning their leading-edge sweep angle and wing planform. In the present work, the initial weight determination, aerodynamic sizing, and planform with and without inlet lip integration, and the conceptual design of a nonconstant leading-edge flying wing UCAV configuration are performed. Next, the obtained conceptual design is downscaled 1:20 to be used as a wind-tunnel model and optimized for low-speed conditions using a kriging-based surrogate model with a vortex-lattice method to maximize the lift-to-drag ratio. Later, the optimized design is validated using an open-source computational fluid dynamics code, OpenFOAM 8.0, to verify the accuracy of the surrogate model and to investigate the aerodynamic characteristics. The optimized UCAV design exhibited improved aerodynamic characteristics in terms of the lift-to-drag ratio. Furthermore, the aerodynamic performance and flowfield of the optimized UCAV model with and without inlet lip integration have been evaluated at low and high speeds.

The design of unmanned combat aerial vehicles (UCAVs) used for military applications is dictated by their low-observability characteristics rather than the aerodynamic performance. Owing to this reason, the UCAVs experience flow separation during takeoff and landing and exhibit stability issues. Moreover, the wing design significantly influences the aerodynamic performance of the UCAV model. The configurations of UCAV models are still under exploration, and the conceptual design of UCAV is still undergoing various developments, so the dimensions and shape of the UCAV design have not been defined yet. Hence, the assessment of the conceptual configurations and their design are worthy issues that need to be investigated. In the present work, the initial weight, aerodynamic sizing, planform selection and then the conceptual design of a non-constant leading-edge UCAV configuration was performed. Later, the obtained conceptual design was optimized using multi-fidelity surrogate models with a vortex-lattice method to achieve a better lift and drag ratio. Lastly, the optimized design was validated using the computational fluid dynamic (CFD) model to verify the accuracy of the surrogate model. It was found that the optimized design exhibited superior lift and drag characteristics compared to the reference design.