Abstract
Aerodynamic forces and moments of a flexible delta wing in its pitching motion were experimentally studied in a low-speed wind tunnel. Three types of flexible delta wings were investigated, the flexible parts of which were 44, 70 and 99% of the delta wing. The pitching motion of the delta wing was changed smoothly and periodically by means of a manipulator equipped with six stepping motors, which were controlled by a microcomputer. Since it had six degrees of freedom, the delta wing could move arbitrarily not only in pitching motion but also yawing, rolling, translation motions, and their combinations. The objective of the research is to analyze dynamic characteristics of the flexible pitching delta wing with comparison to a fully hard delta wing made of metal alloy without its deformation in the motion. A developed compact force balance with the weight of 5.6 grams was used to measure lift, drag and pitching moments. Aerodynamic characteristics were different among the three flexible and hard delta wings, and it was found that the winding-up of the leading edge of the delta wing is a key factor which decides the leading edge vortex on the upside of the wing and the pressure distribution on the windward side. Lift, Cl, drag, Cd and pitching moment, Cpm, made a hysteresis loops with an angle of attack during the pitching motion, especially in the region of a high attack angle accompanied by the leading edge vortex breakdown. Flow visualization for the leading edge vortices were also carried out to explain the dynamic characteristics of the delta wings.
