An experimental and computational aerodynamic investigation of a low-canard high-wing aircraft design

Abstract

An experimental and computational investigation of a low-canard high-wing aircraft design has been conducted. The aircraft studied has a canard and wing of similar chord and airfoil section. The canard is approximately half the span of the main wing and both surfaces are untwisted and unswept. Canard incidence with respect to the zero angles of attack line is 4° and the main wing has an incidence of 1° and a dihedral of 3°.

Force and moment data were obtained in two separate wind tunnel test entries in the VPI Stability Tunnel. The first of these entries were concerned with longitudinal characteristics while the second dealt primarily with lateral/directional characteristics. Flow visualization was also done in both sets of tests. Lift characteristics showed an apparent onset of stall and then a second rise in the lift curve. The aircraft displayed stable characteristics in both the longitudinal and lateral/directional cases. However, the pitch break at the onset of stall was unstable. The “double peak” lift curve as well as the unstable pitch break have been attributed to the canard tip-vortex interaction with the main wing. Test Reynolds numbers were 260,000 for the first set and 300,000 for the second series of tests.

Computational cases were run using both an uncambered vortex lattice method and a general three-dimensional constant doublet and source panel method. Lift curve slope and static margin were obtained from the vortex lattice code and agree well with the experiment. All aerodynamic forces and moments were predicted by the doublet panel method PMARC. Longitudinal data was obtained using a symmetric 3200 panel model while lateral/directional data was taken using a 1600 panel model.

Both the lift curve slopes and the pitching moment slopes compare well between the computational cases and the experimental data. The actual values for a given angle of attack, however, differ and remain unexplained. This is possibly due to either canard wing interaction effects, wind-tunnel-model manufacturing flaws, model mount or tunnel installation interference or a data reduction error.