Documents published in Scipedia

• On the Importance of Fibre Direction Mesh Alignment for Artificial Lightning Strike Simulations

  S. Millen, B. Navagel, A. Murphy

  composites2023.

  
  

  Abstract

  Composite materials, used in primary aircraft structures, produce weight reduction and improved fuel efficiency over legacy metal airframes but are more susceptible to lightning strike damage. Therefore, research into lightning strike damage and protection systems, through experiments and simulations, is an important research topic. For any FE simulation appropriate representation of the material behaviour, the loading and boundary conditions are key to accurate predictions. In addition, an aspect which has been under reported in many studies is the meshing strategy. Fibre direction mesh alignment has been reported to yield more accurate results in the modelling of mechanical damage (intralaminar damage initiation and propagation) in unidirectional fibre reinforced composite structures. However, this model meshing strategy has not found wide application and has not been used for the modelling of thermal damage events, e.g. lightning strike direct effect simulation. Instead, authors have typically refined the mesh around the arc attachment area. This paper, for the first time, examines the influence of fibre direction mesh alignment for artificial lightning strike simulations and the prediction of thermal damage. Initially, the mesh alignment is introduced partially in the central region of the specimen. The paper uses a mature modelling approach with a transient, fully coupled, thermal-electric step in ABAQUS with a lightning test Waveform A (40 kA, 4/20 µs) applied to the specimen. Specimen boundary conditions match those typically used in experiments and a mesh convergence study is undertaken to ensure no element size influence on the results. The use of this meshing strategy has been shown to significantly improve the prediction of both moderate and severe thermal damage profiles, when compared with the standard meshes used in previous research. The predicted moderate (2659 mm2 vs 2833 mm2 ) and severe (1059 mm2 vs 1061 mm2 ) damage areas were improved to within 4% and 1% of experimental results, respectively, using this meshing strategy.

  Abstract
  Composite materials, used in primary aircraft structures, produce weight reduction and improved fuel efficiency over legacy metal airframes but are more susceptible to lightning [...]

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• Coupled problems in bio-inspired robotics

  A. Simone

  coupled2023.

  
  

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• FEM Simulations for Nonlinear Multifield Coupled Problems: Application to thixoviscoplastic flow

  N. Begum, A. Ouazzi, S. Turek

  coupled2023.

  
  

  Abstract

  In this note, we are concerned with the solvability of multifield coupled problems with different, often conflictual types of non-linearities. We bring into focus the challenges of getting EFM numerical solutions. As for instance, we share our investigations of the solvability of thixoviscoplastic flow problems in FEM settings. On one hand, nonlinear multifield coupled problems are often lacking unified FEM analysis due to the presence of different nonlinearities. Thus, the importance of treating auxiliary subproblems with different analysis tools to guarantee existence of solutions. Moreover, the nonlinear multifield problems are extremely sensitive to the coupling. On other hand, monolithic Newton-multigrid FEM solver shows a great success in getting numerical solutions for multifield coupled problems. Thixoviscoplastic flow problem is a perfect example in this regard. It is a two field coupled problem, by means of microstructure dependent plastic-viscosity as well as microstructure dependent yield stress, and microstructure and shear rate dependent buildup and breakdown functions. We adapt different numerical techniques to show the solvability of the problem, and expose the accuracy of FEM numerical solutions via the simulations of thixoviscoplastic flow problems in channel configuration.

  Abstract
  In this note, we are concerned with the solvability of multifield coupled problems with different, often conflictual types of non-linearities. We bring into focus the challenges [...]

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• Modified Kirsch Problem Incorporating Surface Stresses under Plane Stress

  A. Vakaeva, M. Grekov

  coupled2023.

  
  

  Abstract

  We consider the Kirsch problem, taking into account the surface stresses at the boundary of the circular hole and on the front surfaces of the plate, in the framework of the original Gurtin–Murdoch model. The boundary conditions on the cylindrical surface of a circular hole in a nanoplate are derived in terms of a complex variable in the case of the plane stress state. The solution of the two-dimensional problem for an infinite plane with a circular hole under remote loading is explicitly obtained. Based on the analytical solution, we investigated the dependence of the elastic stress field on the nanosised plate thickness and dimension of the hole. Numerical examples are given in the paper to illustrate quantitatively the effect of the plate thickness at the nanoscale on the stress field at and near the cylindrical surface. The results are presented graphically as the dependence of the components of the stress tensor on the polar angle.

  Abstract
  We consider the Kirsch problem, taking into account the surface stresses at the boundary of the circular hole and on the front surfaces of the plate, in the framework of the [...]

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• On Numerical Simulation of Fluid - Structure- Acoustic Interactions Related to Human Phonation Process

  P. Sváček, J. Valášek

  coupled2023.

  
  

  Abstract

  This paper focus on mathematical modelling and numerical simulation of human phonation process. The mathematical FSI model is presented consisting of the description of the structural model, the flow model and the coupling conditions. In order to treat the VFs contact, the problem of the glottis closure is addressed. To this end several ingredients are used including the use of suitable boundary conditions, modification of the flow model and robust mesh deformation algorithm. The FSI model is extended to FSAI problem by inclusion of the Lighthill model of aeroacoustics. The numerical approximation of the problem is presented and several numerical results are shown.

  Abstract
  This paper focus on mathematical modelling and numerical simulation of human phonation process. The mathematical FSI model is presented consisting of the description of the [...]

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• X-Mesh: A new approach for the simulation of two-phase flow with sharp interface

  J. Remacle

  coupled2023.

  
  

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• Sound Insulation Optimization of a Roller Shutter Box

  S. Bakhnouche, W. Larbi, J. Deü, P. Macquart

  coupled2023.

  
  

  Abstract

  This research aims to develop an advanced numerical model to accurately predict and optimize the acoustic insulation performance of roller shutter boxes, which are important for thermal and acoustic insulation in building facades. Traditional laboratory tests for evaluating sound transmission can be expensive and lack repeatability, particularly at low frequencies. To overcome these limitations, the proposed numerical approach utilizes the finite element method to model solid and fluid domains within the roller shutter box structure. Poroelastic layers are accounted for using a mixed displacement-pressure formulation of the Biot poroelasticity equations. Excitation and sound radiation are simulated using a diffuse field of plane waves with random phases and directions, employing the infinite elements method. The numerical model is validated by comparing its results with laboratory tests, which are described in detail. The practical application of this numerical method includes investigating factors such as assembly conditions, positioning of poroelastic layers, and the inclusion of heavy masses on the acoustic behavior of roller shutter boxes.

  Abstract
  This research aims to develop an advanced numerical model to accurately predict and optimize the acoustic insulation performance of roller shutter boxes, which are important [...]

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• Global sensitivity analysis of sound transmission loss of double-wall with porous layers

  S. Bakhnouche, R. Aloui, W. Larbi, J. Deü, P. Macquart

  coupled2023.

  
  

  Abstract

  This study examines the acoustic performance of a double-wall system with a porous layer and conducts a global sensitivity analysis of sound transmission loss. The authors use the transfer matrix method to predict sound transmission, which provides cost-effective modeling of complex acoustic interactions and detailed high-frequency information. The method employs transfer matrices to represent sound wave propagation in each layer, considers material characteristics and layer thickness, and incorporates interface matrices for boundary conditions. The poroelastic layer is modeled using the Biot-Allard approach with nine parameters. Morris and Sobol methods are applied for global sensitivity analysis, identifying significant parameters. The investigation focuses on eleven parameters, including foam properties and layer thicknesses. The findings indicate the impact of geometric parameters at lower frequencies and foam properties at higher frequencies. This study is the first to optimize sound transmission in double-wall systems with porous layers using sensitivity analysis methods, offering insights for system behavior and design

  Abstract
  This study examines the acoustic performance of a double-wall system with a porous layer and conducts a global sensitivity analysis of sound transmission loss. The authors [...]

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• Coupled Simulations of Extreme Fluid-Structure Dynamics

  V. Aune, G. Valsamos, F. Casadei

  coupled2023.

  
  

  Abstract

  This work presents ongoing research on the influence of fluid-structure interaction (FSI) effects on the ductile crack growth in blast-loaded steel plates. Thin steel plates with Xshaped, pre-formed defects are used to allow for large, inelastic strains and ductile fracture. FSI effects were studied by comparing the numerical predictions of the uncoupled and the coupled FSI approach, where experimental data served as a backdrop to evaluate the accuracy of the numerical simulations. Numerical simulations are conducted in the EUROPLEXUS software. The clear conclusion from this study is that ductile fracture and crack propagation are influenced by FSI effects during the dynamic response of the plate. That is, the crack growth was very sensitive to the actual loading on the plate. Moreover, because the increase in CPU cost may be significant when uniformly refining the mesh, adaptive mesh refinement (AMR) was found very promising in reducing the CPU cost and maintaining the solution’s accuracy. The performance of AMR is an interesting finding in the view of numerical simulations of coarsely meshed (prior to AMR) shell structures exposed to blast loading

  Abstract
  This work presents ongoing research on the influence of fluid-structure interaction (FSI) effects on the ductile crack growth in blast-loaded steel plates. Thin steel plates [...]

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• Layered Model of Fluid-Structure Interaction in Dry Wire Drawing with Coupled Axial Velocity

  M. Vervaecke, D. Fauconnier, J. Degroote

  coupled2023.

  
  

  Abstract

  An innovative 2D axisymmetric fluid-structure interaction model of wire drawing is developed to numerically investigate the interaction between the thin lubricant film and the plastically deforming steel wire. The deformation of the wire is obtained from the linear momentum balance and the lubricant film has been calculated by the Navier-Stokes equations. Moreover, the coupling between wire and lubricant is performed by the IQN-ILS technique and a no-slip condition is imposed on the sliding fluid-structure interaction interface. In order to reduce the computational cost, a layering technique is implemented in the axially moving structure domain. This results on the one hand in monitoring the stresses and displacements of the structure and on the other hand in an observation of the hydrodynamic pressure build-up and wall shear stresses in the lubricant. Additionally, the evolution of the fluid film thickness is presented.

  Abstract
  An innovative 2D axisymmetric fluid-structure interaction model of wire drawing is developed to numerically investigate the interaction between the thin lubricant film and [...]

  • 0
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