Further studies of harmonic gradient method for supersonic aeroelastic applications

Recent developments in the applications of the harmonic gradient method (HGM) to various lifting surfaces with/without control surfaces are described. Our objective is to validate the acceleration-potential version of HGM, also known as the ZONA51 code, with available measured data and existing methods, which include the constant pressure panel method, the pressure mode method, and the piston theory. Unsteady supersonic aerodynamics over a leading-edge flap of an F-18 wing and a trailing-edge flap of a British Aerospace Corporation vertical fin are studied. Measured pressure jumps along the flap hinge lines are captured by the ZONA51 code whereas other methods fail to do so. A supersonic flutter analysis is performed for four different wing planforms; these include a 45-deg swept wing, a NASA 70-deg delta wing, a National Aerospace Plane (NASP)-type wing body, and the active flexible wing (AFW). For all cases considered, it is found that the present method yields favorable flutter trends which follow closely with those measured. Conservative flutter boundaries are obtained in almost all cases, in contrast to the predicted results of other existing methods. Finally, the AFW with fuselage and wing-tip ballast store is conveniently modeled and computed by the ZONA51 code resulting in a reasonable flutter boundary. It is believed that the ZONA51 code with its robust structure along with the present validation effort will be upheld as an integral part of matured aeroelastic technology.