09:40
Flutter 2
Chair: Rauno Cavallaro
09:40
30 mins
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Modal Design Optimization for Panel Flutter and Buckling
Kevin McHugh, Cate Leszcz, Joshua Deaton
Abstract: This work investigates a new method to design aircraft skin panels to minimize weight while providing sufficient strength to withstand both buckling due to aerodynamic heating and flutter due to dynamic pressure over the panel. In this work, mass minimization is done via an optimization of panel thickness distribution as opposed to fill-void techniques or methods of adding discrete stiffeners found in the literature or in practice. The thickness distribution and therefore optimization problem is further reduced in numerical order by utilizing a Galerkin projection of global thickness basis functions. The developed tool results in a 6-17% reduction in weight for an optimized panel for thermal buckling stability when compared to the optimally thin flat panel.
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10:10
30 mins
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New Design of Whirl Flutter Aeroelastic Demonstrator
Jiri Cecrdle, Ondrej Vich, Jan Starek, Jarmil Vlach, Martin Kolar, Miroslav Smid
Abstract: The whirl flutter aeroelastic demonstrator (W-WING) represents a half-wing (span 2.56 m) with the nacelle, engine, and propeller (radius 0.35 m). The demonstrator was used for whirl flutter measurements in past. In the frame of the new project, further measurements are planned. Based on the experience, upgrades of the demonstrator were proposed. Submitted paper describes the preparatory activities including the demonstrator design, instrumentation, and aerodynamic and structural analyses.
The main change is the installation of the new motor with the sufficient power. Also, additional sensors and equipment were installed. In addition, the system of steady and unsteady flow field measurement was proposed. Finally, the sting-mounted propeller-nacelle variant (W-STING) was proposed for the measurements of aerodynamic derivatives.
The wing stiffness is modeled by a duralumin spar. The inertia characteristics are modeled by lead weights. The aileron is actuated by the electromagnetic shaker via a push pull rod. The wing is fixed at the root to the pylon. The nacelle model has two DOFs (pitch and yaw). Stiffness parameters are modeled by means of changeable cross spring pivots. Both pivots are independently movable in the direction of the propeller axis. The gyroscopic effect is simulated by the mass of the propeller blades (two sets are available).
The new motor with the sufficient power will enable to operate the propeller in the thrusted mode. The aerodynamic force analytical study using the CFD solver to predict the necessary power and operational margins of the propeller was performed. Based on the results, and on further limitations (mass, dimensions), the motor with the nominal power of 15 kW was selected. The front part of the nacelle was redesigned to accommodate the new motor. The shape of the nacelle remained unchanged. Design also included thrust balance cell, pitch and yaw blocking devices, sliding weight, etc. The appropriate strength checks were performed.
System of sensors include strain gauges in two wing sections, 18 accelerometers in the wing and nacelle, servo-amplifier to manage and monitor the propeller rpm, torque, and immediate power, thrust balance cell, independent optical rpm sensor. W-STING include measurement of pitch and yaw moments and deformation angles.
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