• Structural Equivalence
• PrandtlPlane
• Nastran
• Freeplay
• LCO
• DLM
• Body Freedom Flutter
• Aeroelasticity

Dynamic aeroelastic behaviour of a joined-wing PrandtlPlane configuration is here investigated. The baseline model is a beam model obtained from a configuration previously designed by partner Universities through several multi disciplinary optimizations and several ad-hoc analyses, including also detailed studies on the layout of control architecture.
This represented an ideal starting point since, due to the novel design, realistic layout of the mobile surfaces, stiffness and inertia distributions are not available nor easily deter- minable. An optimization process is defined to build a plate structural model which resembles the reference model’s modal properties. The modal equivalence is pursued on the first five structural modes, in terms of shape and frequencies. The obtained model is considered to qualitatively retain similar aeroelastic properties with great benefits for the applicability of results.
Flutter and post-flutter regimes, including limit cycle oscillations (LCOs) are studied.
A detailed analysis of the energy transfer between fluid and structure is carried out and the areas in which energy is extracted from the fluid are identified, to gain insights on the mechanism leading to the aeroelastic instability.
Starting from an existing design of mobile surfaces on the baseline configuration, freeplay is considered and its effects on the aeroelastic stability properties of the system are investigated.
Both cantilever and free flying configurations are analyzed. Fuselage inertial effects are modeled and the aeroelastic properties studied, considering plunging and pitching rigid body modes. For this configuration a positive interaction between elastic and rigid body modes turns the design in a flutter free one (in the range of considered speed).
To understand the sensitivity of the system and gain insight, fuselage mass and moment of inertia are selectively varied. For a fixed pitching moment of inertia, larger fuselage mass favours the body freedom flutter. When the moment of inertia is varied, a change of critical properties is observed. For smaller values the pitching mode becomes unstable, and coalescence is observed between pitching and first elastic mode. Increasing pitching inertia, the above criticality is posticipated and, in the meanwhile, second elastic mode becomes unstable at progressively lower speeds. For larger inertial values “cantilevered” flutter properties, having coalescence of first and second elastic modes, are recovered.