Aerodynamic Model Identification of the Flying V from Wind Tunnel Data

Abstract

The aerodynamic model identification of a novel aircraft configuration known as the "Flying V" is presented. A global longitudinal aerodynamic model is estimated using static wind tunnel data from a 4.6% sub-scale model. The aerodynamic model structure, unknown a priori, is determined from the data using a modified stepwise regression technique. Orthogonal polynomial models using Multivariate Orthogonal Functions and non-orthogonal spline models in the angle-of-attack dimension are defined for the estimation of the measured aerodynamic coefficients. The estimated models are validated against a partition of the data not used for the estimation, which shows that an adequate model fit and good prediction capabilities are attained. Spline models achieve better results in terms of fitting and show a better matching between the estimation and validation data. All estimated models are considered adequate, with a maximum relative Root Mean Square error below 8% for the polynomial models and below 3% for the spline models. Nomenclature Latin Symbols b Wing span of the half model, [m] c Reference chord, [m] C X , C Y , C Z Force coefficients in body axes, [N] C l , C m , C n Moment coefficients in body axes, [N•m] F Force [N] G Orthogonalization matrix J OLS cost function L, M, N Roll, pitch and yaw moment, [N•m] M Moment, [N•m] n Number of regressors in model N Number of samples p j Original regressors, j = 1, 2, ..., n q Dynamic pressure, [kg•m/s 2 ] S Wing area, [m 2 ] v Residual vector V Wind speed, [m/s] V Dimensionless wind speed, [-] x State vector X Regression matrix X, Y, Z Aerodynamic forces in body axes, [N] y Output vector z Measurement vector Greek Symbols α Angle of attack, [deg, rad] δ Control surface deflection [deg] θ Parameter vector ξ j

Effect of Engine Integration on a 4.6%-Scale Flying-V Subsonic Transport

“…Combining the experience gathered by Palermo [7], Viet [8]and Ruiz Garcia [19] on the testing of the half model Flying V, adding common practice of engine-integration testing, and taking into account the available resources at Delft University of Technology, results in the setup discussed in this section. First the wind tunnel is discussed, followed by a detailed description of the half model and the used measurement equipment and methods.…”

“…The test matrix for the experiment is heavily based on the previously recorded behavior of the Flying V half model. Research done by Palermo [7], Viet [8] and Ruiz Garcia [19] provided the clean-wing trimmable angle-of-attack (AoA) range and optimal CG at 20m/s freestream velocity. The trimmable flight angle-of-attack range of the wing at 20m/s is limited due to a pitch break at 20 • AoA [7].…”

“…From Ruiz Garcia [19] it can be concluded that force coefficients are relatively independent of the airspeed. It is therefore decided to limit the size of the test matrix by testing only at two free-stream velocities.…”

“…With engine calibration done, the wing half model tests are performed to repeat part of the work done by Palermo [7], Viet [8] and Ruiz Garcia [19] for verification and validation purposes. It is hypothesized that the modified setup still leads to similar balance results.…”

Future aircraft concepts and design methods

“…5). However, due to the absence of a tail, a strong coupling between the pitching and heaving movement is experienced which warrants the introduction of dedicated flight control laws for this configuration [13].…”