16:00
Adaptive structures 3
Chair: Sergio Ricci
16:00
30 mins
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Ground resonance test and aeroelastic model validation of an innovative regional aircraft fitted with innovative wing tip (IWT) and adaptive morphing winglet (AMW)
Salvatore Nocerino, Natale Calvi, Biagio De Maio, Salvatore Di Cristofaro, Edoardo Orazi
Abstract: These last years, many economic and financial efforts have been made by the European Commission to encourage more and more the manufacturing of Innovative Regional Aircraft all over the world.
Leonardo is being the leadership of a variety of research project launched in the CLEAN SKY 2 field. The major challenge is the design first and then the fabrication of newer well-designed regional aircraft that can be equipped by either innovative wingtips or adaptive winglets aimed at in-flight load control & alleviation.
On the roadmaps that bring to the permit to fly, aeroelastic clearances must be provided by theoretical analysis using a mathematical model validated by Ground Resonance Test (GRT) data. GRT is aimed at measurement of each Resonance structural mode of the aircraft in terms of frequency, structural damping and modal shape; it has always been a critical issue causing by both significant delay about the aircraft preparation for the flights and how much time is allowed for testing. All this hardly ever fit to the massive time frame asked for Ground Resonance Test.
This paper will describe the GRT performed on the CLEAN SKY 2 demonstrator and the validation method applied for the aeroelastic models of the aircraft fitted with either Innovative Wing Tip (IWT) or Adaptive Morphing Winglets (AMW) that shall be tested in flight. The validated models have been used to provide initial flight clearances as concerns the flutter aspects.
There will be dealt with all characteristic steps for the test campaign running, data post-processing and finally test data correlation with model. Starting off the needed test setup configuration, then moving on to the effective test procedure, next turning to most common algorithms used for the test data post-processing, and at last concluding with the matching between theoretical and experimental modal data for dynamic model updating in use for aeroelastic assessments.
The final goal of GRT is nowadays a very charming chance for getting well-qualified aeroelastic predictions in a short time without any effects on the actual schedules relative to aircraft qualification before the first flight. In this paper it shall be mentioned all technical and operative methods and approaches to meet this commitment.
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16:30
30 mins
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Aeroelastic analysis of a smart SMA-composite wing
Gefferson Silva, Flavio Silvestre, Mauricio Donadon
Abstract: The present work reports on the development of a numerical aerothermoelastic tool that accounts for nonlinearities of multi-physical sources to investigate the behavior of flexible wings made of a hybrid smart material. Here, hybrid materials consist of laminated composites reinforced with embedded shape memory alloy wires. The proposed model gathers geometrical, material, and aerodynamic nonlinearities to the thermal heating dynamics of SMA wires via the Joule effect. To this end, a geometrically nonlinear FE beam model is coupled with material nonlinearities via a micromechanical model that computes the homogenized properties of hybrid laminates. Nonlinear aerodynamic effects are introduced through an unsteady strip theory method in the time domain, along with the assumption of follower aerodynamic forces and a quasi-steady stall model. A set of aerothermoelastic cases was simulated by assuming various layups and SMA temperatures to tailor and analyze the aeroelastic response of hybrid wings. The outcomes have shown a considerable reduction in post-flutter oscillations as the SMA temperature increases, indicating evidence of the capability of hybrid materials for aeroelastic applications.
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17:00
30 mins
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Limit Cycle Oscillation of a Plate with Piezoelectric Elements in Supersonic Flow
Maxim Freydin, Luisa Piccolo Serafim, Earl Dowell, Santosh Varigonda, Venkateswaran Narayanaswamy
Abstract: Fluid structure interaction of an elastic plate with piezoelectric elements, turbulent freestream flow at Mach 2.5, and a pressurized cavity is investigated computationally and correlated with a recent experiment. The pressure field on the surface of the plate is measured using pressure sensitive paint and the structural response is observed using the measured voltage of a piezoelectric patch. The pressure and structural response are investigated in terms of frequency content and amplitude variation over time. The measurements show a dominant frequency of oscillation which indicates the likely onset of flutter and a post-flutter limit cycle oscillation (LCO). A computational investigation is conducted to study the effects of static pressure differential, temperature differential, cavity pressure coupling, and plate boundary conditions on the linear flutter onset condition and the nonlinear post-flutter LCO characteristics. Rivets that connect the plate to the supporting structure are modeled as local constraint in the in-plane direction and their effect on the nonlinear stiffness is investigated. The measured plate natural frequencies outside of the wind tunnel are shown to be closer to pinned than to clamped boundary conditions. Computations show that the coupling between the cavity acoustic and plate structural modes is necessary for flutter onset in the wind tunnel conditions. Direct correlation between computed and measured aerodynamic pressure shows reasonable agreement in amplitude and frequency. Computational results are obtained using Piston Theory and also potential flow aerodynamics, which is more appropriate for the reduced frequency on the order of 1 considered in this work. Lastly, computed and measured pressure LCO mode shapes are extracted and correlated using the spectral proper orthogonal decomposition.
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17:30
30 mins
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Aeroelasticity of smart wing in supersonic flow
Reza Moosavi
Abstract: In the present paper, aeroelastic phenomena of a smart wing in supersonic and hypersonic flows is investigated to represent the flutter alleviation due to piezoelectric effect. Using nonlinear aerodynamic model, a smart wing with pitch and plunge DOFs is simulated. The equations of motion can be obtained by using the Lagrange’s equations and the Kirchhoff’s law. To calculate aerodynamic forces acting on the smart wing in supersonic flow, piston theory can be implemented to model airflow by a quasi-steady compressible method. The complete nonlinear aeroelastic smart wing system can be obtained and divergence and flutter speeds are calculated accordingly.
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