J. T. Viana, J. Romera, G. Pastor, L. Benítez, H. Climent, M. H. Siemann
DOI Number; N/A
Conference number: IFASD-2015-028
Ditching is a planned aircraft event that ends with a controlled emergency landing in water. During the few seconds of the impact phase, large hydrodynamic pressures develop at the interface between the structure and the fluid which in turn may generate damages leading to rupture and cracks on the bottom part of the aircraft fuselage. Ditching is an extreme case of fluid-structure coupling. Currently there are very few available tools to address this problem that is gathering significant attention from public and institutions especially after some recent events with large media coverage (like the ditching on the Hudson River, US Airways Flight 1549, 15 January 2009). At Airbus DS Military Transport Aircraft Aeroelasticity and Structural Dynamics department ditching has been a topic of continuous research for more than 12 years [1-4]. This interest is also shared by universities, research establishments and industrial partners that have gathered together in the consortium of the European funded research project SMAES (Smart Aircraft in Emergency Situations, 2011-2014). This paper will focus on explicit Finite Element (FE) numerical simulations to deal with ditching loads and structural response following two different approaches: — Water is simulated using Smoothed Particle Hydrodynamics (SPH). — Measured pressures from ditching tests are applied to the FE Model. The first part of the paper will be devoted to numerical simulation of ditching scenarios of very stiff panels as they has been tested at CNR-INSEAN during SMAES. Magnitudes simulated will be local pressures, forces and strains on the panel. Numerical results will be extensively compared with available ditching test results obtained in SMAES. The study will show a wide variety of sensitivity analysis to different parameters. The paper will continue with the more challenging task of ditching simulation of flexible panels. Local flexibility affects local pressures which in turn modifies local deformation in a highly coupled fluid-structure interaction phenomena. Comparison of numerical simulations with available SMAES test results will be shown, indicating on one hand what is achievable and on the other, what are the current limitations of the proposed technique for flexible panels. Similitudes and differences between flexible panels and very stiff panels will be highlighted. 1 IFASD-2015-28 The alleviating effect of structural flexibility is one of the most important outcomes of these analyses. It has critical relevance for aircraft ditching certification and it will have a dedicated section in the paper. Concluding remarks highlight how the SMAES project has allowed a large step forward in the understanding of the complex fluid-structure interaction phenomena that takes place during a ditching scenario. In particular, it has allowed enhancing predictive numerical tools. The paper will end with suggestions for further work in this area.