Study On Unsteady Aerodynamic Characteristics Of A Morphing Aircraft

Quasi-steady and unsteady aerodynamic characteristics of a certain axis symmetrical missile,which is designed as a variable-span morphing aircraft or a variable-sweep morphing aircraft,are studied by numerical simulation to explore the unsteady aerodynamic characteristics of the morphing aircrafts during the shape-varying process.And the influence of the flow Maher number,the deformation period and the flight angle on the aerodynamic characteristics of the flow is summarized.Results show: the hysteresis loops of unsteady aerodynamic characteristics of wing during a continuous span-varying process are around the corresponding quasi-steady curves;when the flow Maher number increases,the hysteresis loop increases first and then decreases;when the deformation period becomes smaller,i.e.,deformation rate becomes faster,the hysteresis loop of lift and drag coefficient is larger,steady aerodynamic characteristic curves become more and more deviated from the quasi steady aerodynamic characteristic curves;and the hysteresis loop becomes larger with the angle of attack increases;while the flow is supersonic,the influence of different attack angle and deformation period on unsteady aerodynamic characteristics of the variable-span aircraft is little and the unsteady aerodynamic characteristics is close to the quasi-steady aerodynamic characteristics.So the influence of both factors(attack angle and deformation period)on unsteady aerodynamic characteristics could be ignored in the design process of the missile.But while the flow is subsonic,the influence of variable span on unsteady aerodynamic characteristics could not be ignored.During a continuous sweep-varying process,with the increase of Mach number,the hysteresis loop of drag coefficient and pitch moment coefficient increases at first and then becomes smaller,but the hysteresis loop of lift coefficient has been smaller;when the deformation period is smaller,the hysteresis loop of the aerodynamic parameters becomes larger;the hysteresis loop becomes larger with the angle of attack increases.And the unsteady aerodynamic characteristics during a continuous span-varying process is more significant than the unsteady aerodynamic characteristics during a continuous sweep-varying process.