13:30   Very flexible aircraft 3 Chair: Raymond kolonay 13:30 30 mins Effect of gust models on the response prediction of a very flexible wind tunnel wing model Stefanie Düssler, Christoph Mertens, Rafael Palacios Abstract: The modelling capabilities of a nonlinear aeroelastic simulation toolbox regarding its gust response prediction of a very flexible wing are exercised against the wind tunnel experiment of the Delft-Pazy wing. Sectional force corrections are employed to capture low Reynolds number effects and the static lift deficiency at high angles of attack due to the onset of separation. With these corrections, both the steady and dynamic wing deformations match the experimental results well. We further simulated the unsteady inflow to the Delft-Pazy wing that is produced by the gust vanes in the wind tunnel simultaneously with the wing itself, instead of using a frozen gust model. The results of this simulation indicate a considerable influence of the wing's presence on the gust velocity that was measured upstream of the wing in the wind tunnel experiment. The structural response differs only slightly utilizing the two different gust models, confirming the frozen gust model being a valid assumption for the moderately large deflections of the Delft-Pazy wing. Possible geometrical nonlinear effects are assessed and are found to become apparent for this wing because of the nonlinear aeroelastic equilibrium but not the gust excitation itself. 14:00 30 mins Evaluation of Aeroelastic Models for Gust Response Prediction in Very Flexible Wings Divya Sanghi, Cristina Riso, Carlos Cesnik Abstract: This paper compares aeroelastic models for gust response prediction in very flexible wings. The investigations focus on the Pazy wing benchmark developed at Delft University of Technology for gust response experiments in low-speed flow. The comparisons consider two geometrically nonlinear aeroelastic models of the wing, which comprise an equivalent beam representation of the structure coupled with unsteady potential flow aerodynamics based on either strip theory with wingtip corrections or the vortex-lattice method. The study examines wing responses to 1-cosine vertical gust inputs for various maximum gust velocities, flow speeds, and root angles of attack, exciting a wide range of deflections. The aeroelastic models based on corrected strip theory and the unsteady vortex-lattice method predict maximum wing tip vertical displacements that differ by less than 3%. The models also agree on the characteristic frequency and phase during the free decay after the gust. However, the model based on strip theory predicts a faster free decay due to higher aerodynamic damping, consistent with findings from previous flutter investigations focused on the Technion Pazy wing. These results provide new insights into the impact of model complexity on aeroelastic prediction accuracy for very flexible wings, expanding the scope of previous studies to encompass gust responses. 14:30 30 mins Highly Flexible Aircraft Flight Dynamics using CFD Alain Dugeai Abstract: The present study has been carried out in collaboration with Airbus, in the frame of the French DGAC funded project MAJESTIC. This project is devoted to the study of the civil aircraft high aspect ratio adaptive wing (HAR). Today, the typical aspect ratio value of a civil aircraft wing is about 9. In MAJESTIC, several versions of the XRF1 Airbus model of aspect ratio 12 and 14 are evaluated. For such configurations, wing flexibility becomes prominent and aeroelastic effects have to be taken into account in order to properly analyse the aerodynamic performances of the aircraft. Moreover, structural integrity due to strong aeroelastic effects has to be assessed, in such cases as flutter, control surfaces reversal and gust response. Aeroelastic design is crucial in order to deliver a configuration fully satisfying the multi-disciplinary constraints and global performances needed to meet drastic climate impact reductions objectives. In addition, due to the large wing span, the coupling of structural modes of low frequency and flight dynamics modes comes in the scope of the study. The present paper focuses on the development of a numerical CFD methodology for the simulation of the flight dynamics of the flexible aircraft, in open loop and in closed loop as well (Figure 1). To do so, a modular environment is developed to couple the ONERA CFD solver elsA with python modules implementing several simulation capabilities: prescribed complex trajectory, 6 DoFs flight dynamics, structural linear dynamics, control surfaces actuations, control laws. The basic assumptions and numerical features of the developed environment are presented along with a reminder of the unsteady deformable capabilities of the elsA code, and several applications performed in the frame of the MAJESTIC project on the HAR XRF1 configurations are shown. In particular the topic of the simulation of active Gust Load Alleviation is examined. Perspectives are given on the future extension of the approach to the accounting for non-linear structural behaviour, and the possible use of other CFD solver such as CODA or the ONERA next generation solver SoNICS. 15:00 30 mins Aeroelastic challenges in the clean aviation hybrid-electric regional aircraft project Emilio Santos, Alan Serena, Mordechay Karpel, Felix Arevalo, Hector Climent Abstract: Air vehicles operating in inter-urban regional connections could take benefit of adopting hybrid-electric propulsion technologies and associated complementary solutions for reducing the environmental footprint of aviation, towards climate neutrality. Airbus Defence and Space is partner of a consortium which, as part of the Clean Aviation Strategic Research and Innovation Agenda (SRIA), is responsible of the engineering solution of a short-range (500-1000 km) Hybrid-Electric Regional Aircraft, one of the new aircraft architectures that will thrust the aviation towards 2050 climate neutrality. This paper summarises the aircraft architecture solution and the aeroelastic challenges/technologies that will be developed during the different phases of the project. Some of the technologies developed for supporting the design of the HERA aircraft are: 1. The Hybrid-Electric Regional Architecture (HERA) aircraft will include distributed propeller-type propulsion with inertia and aerodynamic impacts on wing component that shall be considered thru high-fidelity simulations. These simulations are performed using a Fluid-Structure Interaction (FSI) procedure based on MSC/.Nastran coupled with different High-Fidelity aerodynamics solvers. A graphical workbench DYNFSI is being developed to increase robustness and enhance the user experience when calculating 1-way or 2-way unsteady aerodynamics. 2. The rigid-body response of the aircraft will be improved by introducing the Integrated Flexible Aircraft Model (IFAM), with improved coupling between flight mechanics and aeroelastic formulation, all integrated in the industrial procedure of Airbus Defence and Space (DYNRESP and DYNLOAD tool suites) to calculate Dynamic Loads. The Structural Dynamics and Aeroelasticity in the HERA project will be described with emphasis on the previous two points, declaring the maturity status on each of them and future activities up to 2026 (LCOs/flutter suppression activities, wind-tunnel tests, digitalization of methods and tools, etc.) References: Clean aviation HERA project: https://www.clean-aviation.eu/hybrid-electric-regional-aircraft M. Karpel, M. Weiss, J. Barrera, E. Santos, F. Arévalo, and H. Climent, Aeroservoelastic Response and Stability Framework with Computational Aerodynamics, AIAA SciTech Forum, 2020 M. Reyes, H. Climent, M. Karpel, F. Arévalo, and C. Maderuelo, Examples of increased-order Aeroservoelastic modelling, CEAS Aeronautical Journal, 2019 D.H. Baldelli, P.C. Chen, and J. Panza, Unified Aeroelastic and Flight Dynamic Formulation via Rational Function Approximations, Journal of Aircraft, Vol. 43, No. 3, May-June 2006

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