Blunt-nosed, highly-swept crescent wings, often found in flying wing designs like the Flying V, offer high aerodynamic efficiency but exhibit nonlinear aerodynamic behavior at high angles of attack. This study experimentally investigates the vortical flow over the Flying V under these conditions at a Reynolds number of 8.0x10^5 and a Mach number of 0.10. Balance measurements assess the aerodynamic performance, while oil flow visualization captures the on-surface flow topology. A 7-hole pressure probe maps the off-surface flow topology above the wing’s suction side. Results reveal a double vortex system (in- and outboard vortex) forming over the inboard wing starting at AOA = 12.5°. At AOA = 15.0°, the stronger outboard vortex merges with another vortex over the outboard wing, which develops aft of the leading-edge kink at AOA = 7.5°. The vortical flow enhances the aerodynamic performance through vortex lift between AOA = 10.0° and 18.0°. However, at the latter angle, a pitch break occurs, attributed to the breakdown of the inboard vortex and the upstream movement of its onset and breakdown locations. Balance data indicate that the vortex breakdown is asymmetric, occurring first over the starboard wing.@en

The Flying V is a flying wing aircraft consisting of two pressurised passenger cabins placed in a V shape. Its longitudinal and lateral control is ensured via elevons and split flaps on the outboard wing, and rudders on the tip-mounted winglets. The goal of this study is to devise a design for the outboard wing of the Flying V through a constrained aerodynamic shape optimisation at cruise conditions. The design process is divided into a geometry preparation phase in which the existing parametrisation is adjusted, followed by a planform design optimisation guided by the Differential Evolution algorithm making use of a vortex-lattice method and an Euler flow analysis. The cross-sectional shape of the wing is subsequently optimised through a Free-Form Deformation (FFD) shape optimisation based on the Euler equations. Two FFD optimisations are conducted to evaluate the effect of the integration of the elevons. The highest lift-to-drag ratio is obtained by neglecting the control surface integration and amounts to 20.3. While the constraints related to this elevon integration reduce the efficiency to 19.4. The overall efficiency gain compared to the original aircraft design is equivalent to 13% and 8%, respectively. A further increase is expected once the inefficient outboard wing is optimised in more detail.

@en