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The presented work is being done within EU CRAHVI G4RD-CT-2000-00395 programme, with the support from the European Community[1]. Differently to the previous EU "crash" programmes dealing with aircraft safety (restricted to vertical 10 m/s crash speed), the current one is more dedicated to high velocity problems, meaning in our case that we now are...
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... level of pressure and distortion are in good agreement with the expectations. The following figure 6 presents the deformation of the ALE mesh at the maximum penetration of the impactor. We can also note that this type of modeling permits to simulate the wave and bears an important mesh deformation. ...
Citations
... The Finite Element (FE) method, with a Lagrangian framework, is usually used to model the structure. The fluid behaviour can be described by various methods: Lagrangian [15], Eulerian [16], [17], Arbitrary Lagrangian-Eulerian (ALE) [18], or mesh-free methods such as Smoothed Particle Hydrodynamics (SPH) [16]. ...
... Simulations numériques d'impact à l'eau Les professionnels de l'aéronautique utilisent la simulation numérique pour l'impact à l'eau, principalement dans le cadre d'études sur l'amerrissage d'aéronef [Ortiz 2004], [Ortiz 2002 [Greenhow 1983]. Les résultats sont comparés sur la Xiao [Xiao 2014] propose une analyse numérique de l'impact d'un cylindre déformable et rigide sur de l'eau. ...
... En ce qui concerne le projet BELOCOPA, des simulations d'impact d'un fuselage d'aéronef à l'eau permettraient, à l'instar d'Ortiz [Ortiz 2002], de connaitre les conditions plus proches d'un crash en mer. Elles pourraient alors être appliquées au système. ...
... Description lagrangienne à gauche et eulérienne à droite dans Abaqus .La plupart des articles utilisent une description eulérienne pour l'impact à l'eau[Ortiz 2002],[Aquelet 2004]. Cependant il est aussi possible d'utiliser des éléments finis en description lagrangienne mais cela implique des problèmes de distorsions d'éléments[Constantinescu 2006]. ...
The objective of this work is to propose approaches to model and to assess experimentally the structural impact on different media. A variety of analytic models and numerical simulations are developed comparing to experimental results. The first part of this work presents a discussion on the similitude between a water impact and an impact on a deformable solid structure. Water impact simulations of a deformable cylinder (without rupture) are performed by finite elements (FE, Coupled Eulerian Lagrangian) and SPH analysis. An analytical model of water impact is proposed for the prediction of peak force evolution. The analysis of results permits to design an impact programmer reproducing this peak force. FE longitudinal impact simulations on cylindrical tubes, with an adapted geometry, are performed and compared with some experiments. The “dynamic buckling” of tubes under impact (due to the material inelastic behavior and to strain waves) is observed. The second part deals with the low velocity perforation (< 10 m/s, strain rate < 1000 s-1) of thin plates. Some experiments on an instrumented drop test (force, displacement, plate shape, crack propagation) are analyzed. Shell FE simulations, with a damage rupture criteria implemented are performed. Parameters are identified by inverse method with the help of Charpy tests made on 2024 T3 aluminum alloy. An analysis of the peak force, during impact, leads to a good understanding of the perforation mechanism. In parallel, a new analytical model, based on an energetic approach of the perforation, is proposed and compared with FE simulations. The numerical perforation study is extended to high velocities and high strain rates (100 - 1000m/s, strain rate < 100 000 s-1) in order to identify different well-known transitions of perforation (Petalisation, petals' fragmentation, total plate's fragmentation).
... Kindervater [18] discusses the crashworthiness of an A320 fuselage section onto a rigid surface, as well as the ditching of transport aircraft on water and highlights the limitations in water modelling. Ortiz [80] and Delatombe [81] defined the standard configuration for a ditching event of an Airbus A321: pitch angle 8 degrees, vertical and horizontal velocity of 1.5 and 65m/sec respectively. Using RADIOSS, this attempt in 2004 paved the way for further developments in the code, as the authors demonstrated a large numerical step forward over existing efforts, by considering damage and failure in a deformable structure (Fig. 19). ...
... The accuracy of a coupled simulation depends heavily on the number of SPH water particles as insufficient particle count provides poor correlation [80]. Analogous to mesh convergence studies, demonstration of particle convergence is essential. ...
This paper reviews the development and application of numerical methods to structural hydrodynamic loading. Fluid-structure interaction is complex, as the ideal code must be able to handle non-linearities, predict thin walled structural collapse (accumulation of plasticity, damage and failure), in addition to capturing the physical response of water (cavitation, suction, and aeration). No single numerical method is able to do all efficiently. Originally developed for aerospace problems, the Crashworthiness, Impacts and Structural Mechanics Group (CISM) at Cranfield University has applied its coupled FE-SPH capability to both Aerospace and Offshore engineering problems.
This paper is split into several parts. First, an overview of previous analytical, experimental and numerical studies into water impact research will be provided to understand the different structural collapse mechanisms between hard and water surfaces. This research provided the framework for a coupled Finite Element-Smooth Particle Hydrodynamic (FE-SPH) approach, where key principles will be reviewed and functionally demonstrated through progressively complex offshore examples, including tethered buoys and green water loading on ship superstructures.
Limitations of a coupled FE-SPH code will be presented by considering aircraft ditching through a Cranfield co-ordinated European FP7 project, SMAES (SMart Aircraft in Emergency Situations). For ditching certification, allowances are made for “probable” structural damage, which is where developments in numerical methods are required. Equally applicable to Offshore, ditching places considerable demands on water modelling due to deficiencies in modelling flow phenomena such as air cushioning, cavitation, suction and ventilation effects. These issues will be explored in order to provide a roadmap for future methods development, which will benefit both Aerospace and Offshore communities.
... Hua et al. [358] studied the ditching of a commercial airplane's finite elements with the arbitrary Lagrange-Euler (ALE) technique for the fluid domain. Comparisons of numerical results obtained using the SPH method and experimental results were presented by Anghileri et al. [359][360][361] and others [362][363][364][365][366][367]. Several authors have studied the possible ditching of a space shuttle [368][369][370][371] and the water impact of the passenger compartment of the Challenger space shuttle [372,373]. ...
This report presents an in-depth review of the current state of knowledge on hull slamming, which is one of several types of slamming problems to be considered in the design and operation of ships. Hull slamming refers to the impact of the hull or a section of the hull as it reenters the water. It can be considered to be part of a larger class of water entry problems that include the water landing of spacecraft and solid rocket boosters, the water landing and ditching of aircraft, ballistic impacts on fuel tanks, and other applications. The problem involves the interaction of a structure with a fluid that has a free surface. Significant simplifications can be achieved by considering a two-dimensional cross section of simple shape (wedge, cone, sphere, and cylinder) and by assuming that the structure is a rigid body. The water is generally modeled as an incompressible, irrotational, inviscid fluid. Two approximate solutions developed by von Karman (1929, "The Impact on Seaplane Floats During Landing," NACA Technical Note NACA-TN-32) and Wagner (1932, "Uber stoss und Gleitvorgange an der Oberache von Flussigkeiten," Z. Angew. Math. Mech., 12, pp. 192-215) can be used to predict the motion of the body, the hydrodynamic force, and the pressure distribution on the wetted surface of the body. Near the intersection with the initial water surface, water piles up, a jet is formed, and the solution has a singularity in this region. It was shown that nearly half of the kinetic energy transferred from the solid to the fluid is contained in this jet, the rest being stored in the bulk of the fluid. A number of complicating factors are considered, including oblique or asymmetric impacts, elastic deformations, and more complex geometries. Other marine applications are considered as well as applications in aerospace engineering. Emphasis is placed on basic principles and analytical solutions as an introduction to this topic, but numerical approaches are needed to address practical problems, so extensive references to numerical approaches are also given. [DOI: 10.1115/1.4023571]
... In a first study [1,2] ONERA performed some ditching simulations with a coarse F.E. model. The aim was to show the feasibility of such a simulation. ...
The presented work has been done within EU CRAHVI G4RD-CT-2000-00395 programme, with the support of the European Community. Differently to the previous EU "crash" programmes dealing with aircraft safety, the current one is more dedicated to high horizontal velocity problems. Another specificity of the programme is that it is concerned with problems such as bird, debris or ground obstacles impacts, and crash on rigid or soft soils. The proposed paper presents hard landing simulations of large aeronautical structures using explicit F.E. codes, such as RADIOSS. The main technical difficulties arise from the dimensions and the complexity of the structures to be modelled on the one hand, and from the complexity of the very local ruin phenomena (rupture of material or failure of riveted joints) on the other hand. When we study aircraft behaviour, it becomes necessary to consider different configurations (nature and stiffness of the impacted surface). The other aim of the project is to improve confidence and assess representativness of models for ditching simulations.
During aircraft landing on water, the intense impact load may lead to significant local deformation of the fuselage skin. Ensuring the aircraft’s integrity and reliability is of paramount importance. This paper investigates the fuselage skin’s dynamic response during water entry. In the simulation of complex water entry problems, the smoothed particle hydrodynamics (SPH) method can fully leverage the advantages of the particle method. However, the traditional SPH method still suffers from the drawbacks of tensile instability, significantly affecting the computational accuracy. Therefore, this paper first introduces the improved SPH model addressing fluid and solid tensile instability issues. Furthermore, the Riemann-based contact algorithm at the fluid–solid interface is also demonstrated. Based on the above improved SPH model, the simulation of water entry of the elastic cylinder is performed to validate the efficacy of the improved SPH model. Then, the dynamic response characteristics of elastic fuselage skin and the skin–stringer–floor–column structure when it enters the water are analyzed, including the deformation features and slamming force. Lastly, based on the presented damage model, a study is conducted on the water entry of the metallic elastic–plastic skin–stringer–floor–column structure, analyzing the locations of failure and providing guidance for the structural safety design of engineering.
The present study addresses the development and validation of a smoothed particle hydrodynamics (SPH) method, particularly to examine its feasibility and capability in hydrodynamics and dynamics of aircraft during idtching. The developed method solves the weakly compressible Navier–Stokes equations coupled with six-degree of freedom dynamics to achieve an accurate prediction of the interaction between the aircraft and the fluid. In this SPH method, a dummy particle wall-boundary condition is automatically implemented to meet the requirement of application on geometrically complex engineering problems. An efficient particle search strategy merging the ideal of Cell-linked list with Vertlet list is proposed to speed up the neighbor particles search process. The present SPH method uses an OpenMP memory-shared parallelization in conjunction with Z-curve reordering to accelerate the computation. Validations have been performed on several classic hydrodynamic problems, where good agreements were achieved via comparing with documented experimental results. The developed SPH method is applied to predict the ditching event of a complex helicopter model. Results demonstrate the ditching process, indicating that the method can be potentially used in aircraft ditching applications.
The paper reviews work undertaken in the field of water entry between 1929 and 2003, providing a summary of the major theoretical, experimental and numerical accomplishments in the field. The review commences with an outline of early theoretical and experimental investigations into water entry between 1929 and 1959. During this period, the first physical models and mathematical detailing of the problem enabled the calculation of water impact forces. Work on the application of such theories to spacecraft water landing is then reviewed commencing with theoretical and experimental analysis of the first manned spacecraft, followed by further applications including early water impact analysis of the space shuttle solid rocket boosters and water landing characteristics of the orbiter.Following the work on the water landing of spacecraft, more recent developments in the theoretical, experimental and numerical modelling of water impact are reviewed. Recent research on the applications, in particular, numerical modelling techniques, to the water impact crashworthiness of aerospace structures is then reviewed. This part of the review highlights the particular problems encountered with the validation of numerical models. Finally, future directions for research in the field of water entry are discussed including the development and validation of numerical modelling techniques and analysis of the failure of both metallic and composite materials during water impact.
