Aerodynamic Design of a Flying V Aircraft in Transonic Conditions

The Flying V is a long-range, flying-wing aircraft where payload and fuel both reside in a V-shaped, crescent wing with large winglets that double as vertical tail planes. The objective of this study is to maximize the lift-to-drag (L/D) ratio of the Flying V in cruise conditions, i.e. CL= 0.26, M = 0.85 and to investigate its off-design performance in high-subsonic conditions. This is done by manually modifying the design parameters that describe the outer mold line of the Flying V and assessing the aerodynamic performance by means of computational fluid dynamics. A 15-million cell, third-order MUSCL, Reynolds-Averaged Navier Stokes solver with the Menter SST turbulence model is used to estimate the aerodynamic coefficients. This numerical model is validated using the experimental data of the ONERA M6 wing. A new, CATIA-based, parametrization of the Flying V is the starting point of the design. Three manual design phases improve the aerodynamic performance while satisfying all constraints. Design modifications include an increase in camber and aft-loading of the wing around 40% of the semispan and improved airfoil sections on the outboard wing generating the required lift coefficient towards an elliptical lift distribution. The twist distribution at the wing-winglet junction is optimized to reduce wave drag. This has resulted in an improvement of L/D from 20.3 from previous studies to 24.2 for the final version, while reducing the cruise angle of attack from 5.2 to 3.6 degrees. The drag divergence Mach number is estimated at 0.925.AerodynamicsGroup De BreukerFlight Performance and Propulsio

Aerodynamic Model Identification of the Flying V from Sub-Scale Flight Test Data

This paper presents the identification of the aerodynamic model of the "Flying-V", a novel aircraft configuration. The aerodynamic model is estimated using flight test data from a 4.6\% sub-scale model. The dataset includes longitudinal and lateral-directional maneuvers performed by both the pilot and the autopilot to excite the aircraft dynamic modes. The so-called Two-Step Method is used to decouple and simplify the aerodynamic identification problem; the state estimation step is performed by an Iterated Extended Kalman Filter, and the parameter-estimation step using ordinary least squares. A stepwise regression technique and previous knowledge from wind-tunnel tests are combined to select the model structure, and the identified model is validated using a third of the gathered data. The estimated models are parsimonious and considered adequate in terms of model fit, with a maximum relative Root Mean Square Error of 10% for the worst validation case. For the considered location of the center of gravity and flight conditions, the estimated aerodynamic derivatives confirm that the aircraft is longitudinally stable, both statically and dynamically; and that it is also laterally and directionally statically stable. The analysis of the dynamic modes of the sub-scale model showed stable short period and roll subsidence modes, a lightly damped Dutch roll mode, and lightly damped/unstable phugoid and spiral modes.Flight Performance and PropulsionAerospace Structures & Computational Mechanic