Finite Mass Simulation Techniques in LS-DYNA

Tutt, Benjamin; Roland, Scott; Noetscher, Greg; Charles, Richard

doi:10.2514/6.2011-2592

Cited by 26 publications

(17 citation statements)

References 1 publication

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“…In this study, the fluid mesh is controlled by the dummy motion. Tutt and his colleagues shew a first application of this technique on scaled models 11 .…”

Section: Finite Mass Type Simulationsmentioning

confidence: 99%

Improvements in Fluid Structure Interaction Simulations of Parachutes Using LS-Dyna®

Coquet¹,

Bordenave²,

Capmas

et al. 2011

21st AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar

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The French Ministry of Defence's procurement agency, the Direction Générale de l'Armement (DGA), is in charge of assessing and testing armament systems in order to equip the armed forces and prepare for the future. DGA Aeronautical Systems, the technical centre dedicated to evaluate and test aircraft, combines test and evaluation to clear, among others, parachute systems. The parachute evaluation is historically based on experimental data and so requires numerous flight tests which can prove expensive and time consuming. In order to have a greater understanding of the parachute dynamic behavior and to optimize the parachute systems flight tests, DGA Aeronautical Systems developed a modeling and simulation capability as a support to evaluation. For this purpose, DGA Aeronautical Systems, with the help of ISAE, developed Fluid Structure Interaction (FSI) simulations of parachutes using the LS-Dyna commercial Finite Element Analysis (FEA) tool. This tool is largely used for solving highly nonlinear transient problems and enables doing coupled multi-physics simulations such as FSI simulations. DGA Aeronautical Systems has been using the software since 2003. In the recent years, the parachute simulation has been much improved thanks to the implementation of a porosity algorithm in LS-Dyna at the common request of DGA and parachute industry. The paper presents recent improvements in Arbitrary Lagrangian Eulerian (ALE) techniques used to analyze the canopy inflation and the quasi-steady state descent phases characteristics. Up to now, only infinite mass type simulations were developed by constraining the parachute confluence point and applying a prescribed airflow to the fluid. The applied airflow velocity came from real in-flight measurements of paratrooper or load trajectory determinations. This simulation type is representative to wind tunnel tests. From now on, thanks to considerable computational resources, finite mass type simulations are also possible. It consists in applying the force of gravity to the parachute system. This allows simulating both the inflation phase (from vertical packed parachute geometry) and the quasi-steady state descent. Among others, the static line parachute of the new French Army troop parachute system called EPC (Ensemble de Parachutage du Combattant) was modeled at real scale. Modeling techniques are presented and results of the EPC static line parachute simulation are compared with real inflight measurements. The benefits of FSI simulations prior to parachute testing are presented. In a near future, incompressible and compressible Navier-Stokes solvers will be available in the next version of LS-Dyna. These code enhancements will be tested to simulate the parachute flight and hopefully will bring the ability to analyze more accurately the aerodynamics of the canopy and the structural behavior of the fabrics. These future capabilities are also discussed.

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“…In this study, the fluid mesh is controlled by the dummy motion. Tutt and his colleagues shew a first application of this technique on scaled models 11 .…”

Section: Finite Mass Type Simulationsmentioning

confidence: 99%

Improvements in Fluid Structure Interaction Simulations of Parachutes Using LS-Dyna®

Coquet¹,

Bordenave²,

Capmas

et al. 2011

21st AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar

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“…Other analysis techniques based on inmersed boundary methods have been applied by Kim and Peskin (2009), large-eddy simulation by Karagiozis et al (2011) and Front-Tracking methods by Kim et al (2013). Moreover, applications of the simulation software package LS-DYNA s (LS-DYNA) to steady-state flight and opening of parachutes have been presented by Tutt et al (2010).…”

Section: Introductionmentioning

confidence: 98%

Simple and efficient numerical tools for the analysis of parachutes

Flores

Ortega

Oñate

2014

Engineering Computations

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Purpose -The purpose of this paper is to describe a set of simple yet effective, numerical method for the design and evaluation of parachute-payload system. The developments include a coupled fluidstructural solver for unsteady simulations of ram-air type parachutes. The main features of the computational tools are described and several numerical examples are provided to illustrate the performance and capabilities of the technique. Design/methodology/approach -For an efficient solution of the aerodynamic problem, an unsteady panel method has been chosen exploiting the fact that large areas of separated flow are not expected under nominal flight conditions of ram-air parachutes. A dynamic explicit finite element solver is used for the structure. This approach yields a robust solution even when highly nonlinear effects due to large displacements and material response are present. The numerical results show considerable accuracy and robustness. Findings -A simple and effective numerical tool for the analysis of parachutes has been developed. Originality/value -An analysis code has been developed which addresses the needs of ram-air parachute designers. The software delivers reasonably accurate results in a short time using modest hardware. It can therefore assist the design process, which nowadays relies on empirical methods. IntroductionThe numerical simulation of parachutes is a challenging coupled problem. From the structural point of view, parachutes are complex in design and behaviour. Braced membranes, such as parachute canopies, cannot equilibrate an arbitrary set of loads unless drastic geometrical changes take place; thus, the structural response is extremely nonlinear. The lack of bending stiffness of the structural components makes them buckle (wrinkle) under compressive loads, exhibiting an asymmetric behaviour. Moreover, the interaction and contact between the different structural elements often has to be accounted for in order to properly model the problem. The flow surrounding the parachute is also complex and highly unsteady in some flight stages of the parachutes (e.g. deployment and inflation). The aerodynamic model adopted should also account for massive flow separation, the presence of large unsteady wakes and aerodynamic interactions between the structural components. The nature of the applied forces, which depend heavily on the structural response of the parachute, adds an extra layer of complexity to the analysis. As the magnitude and direction of the aerodynamic forces (mainly follower pressure loads) are not known in advance but

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“…However, this method consumes a large amount of co mputing r esources, a nd t he t otal n umber o f e lements must be controlled within some range. Moreover, since this method applied in most engineering practices is based on a laminar model (Coquet et al 2011;Tutt et al 2011), t he results are rougher in c alculating high Re number flow field.…”

Section: Introductionmentioning

confidence: 98%

“…ἀ e r epresentatives a re a rbitrary L agrangian-Eulerian (ALE) method (Coquet et al 2011;Tutt et al 2011), the immersed b oundary (IB) m ethod (K im, P eskin 2009), etc. (Kenji 2012;P otvin et al 2011).…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study of Parachute Inflation Based on a Mixed Method

Cheng

Wei

et al. 2012

Aviation

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ἀ e C9 parachute was the research object in this work and was studied by using a fluid-structure interaction method and CFD method. An arbitrary Lagrangian-Eulerian method, a kind of fluid-structure interaction method, was used to simulate the inflation process. ἀ e dynamic relationship between canopy shape and flow field was obtained. ἀ e canopy shape in a stable phase was exported and was transformed into the porous media domain. ἀ en the flow around the canopy shape was simulated by the CFD method we used based on the k-ε turbulence model. ἀ e experiments verified the accuracy of structural change and the feasibility of the porous media model. ἀ e arbitrary Lagrangian-Eulerian method not only can obtain the dynamic results of structure and flow field but also can provide a more accurate bluff body for further CFD analysis. ἀ e CFD method based on porous media and the turbulence model can obtain more detailed and accurate flow field results, which can be used as a complement to fluid-structure interaction analysis. ἀi s mixed method can improve the accuracy of analysis and be useful for other permeable fabric research.

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Finite Mass Simulation Techniques in LS-DYNA

Cited by 26 publications

References 1 publication

Improvements in Fluid Structure Interaction Simulations of Parachutes Using LS-Dyna®

Improvements in Fluid Structure Interaction Simulations of Parachutes Using LS-Dyna®

Simple and efficient numerical tools for the analysis of parachutes

A Numerical Study of Parachute Inflation Based on a Mixed Method

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