Documents published in Scipedia

• Lattice Boltzmann simulation of a deploying Krueger device

  J. Ponsin, C. Lozano

  eccomas2022.

  
  

  Abstract

  In this paper, we describe the numerical simulations carried out within the H2020 UHURA project of the turbulent unsteady flow generated during the motion of a Krueger device for laminar wings using a commercial lattice Boltzmann solver based on a Wall-Modelled LES approach. The simulations are focused on reproducing one of the experimental test cases carried out in the ONERA-L1 wind tunnel during the UHURA project. The numerical method and the simulation setup are described. The simulation results are compared with the high-quality experimental data obtained in the ONERA-L1 wind tunnel in order to assess the accuracy of the predictions.

  Abstract
  In this paper, we describe the numerical simulations carried out within the H2020 UHURA project of the turbulent unsteady flow generated during the motion of a Krueger device [...]

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• Numerical investigation of Hydrogen self-ignition and deflagration-to-detonation phenomena using automated meshing approach and detailed chemistry

  M. Cojocaru, L. Sufrà, P. Scienza

  eccomas2022.

  
  

  Abstract

  Computational fluid dynamics (CFD) plays a critical role in designing safe storage and transport systems for hydrogen. Fine mesh resolution and detailed chemistry are essential for the accurate prediction of self-ignition and deflagration-to-detonation (DDT) in hydrogenair mixtures. However, simulating H2 venting and explosion in real-life scenarios (e.g., with complex obstacle shapes and a large computational domain) involves tedious meshing effort and several mesh iterations to capture flame and shock locations. This paper addresses these challenges by assessing the capability of a detailed-chemistry approach combined with automated meshing based on a cut-cell technique and Adaptive Mesh Refinement (AMR). Furthermore, three different turbulence-chemistry interaction modelling approaches are compared for self-ignition and DDT scenarios: a homogeneous reactor model, an eddy dissipation model, and a flame thickening approach.

  Abstract
  Computational fluid dynamics (CFD) plays a critical role in designing safe storage and transport systems for hydrogen. Fine mesh resolution and detailed chemistry are essential [...]

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• Finite element model of kurpsai dam in kyrgyzstan based on actual response measured by extensive network of various sensors

  S. Takhirov, S. Orunbaev, E. Toshmatov, R. Shamansurov, R. Shamansurov, Z. Baiyzbekov

  eccomas2022.

  
  

  Abstract

  The paper presents recent results of an ongoing collaborative research project focused on modelling the Kurpsai water dam in Kyrgyzstan. The research team includes scientists and engineers from the USA, Kyrgyzstan, and Uzbekistan. This water dam was selected for modelling because of the recent installation of an extensive network of various sensors aimed at monitoring its performance under seasonal changes, ambient vibration, and seismic excitation. The installed instrumentation network includes the following sensors: (1) a set of fiber-optic strainmeters and temperature meters, (2) a set of velocimeters for seismic monitoring, and (3) a set of GNSS receivers to measure absolute static displacements. A 3D model of the water dam was generated based on a utilization of the finite element approach. As a starting point the water dam’s concrete was assumed to be elastic material. The latter assumption is considered acceptable, because (as of today) only responses to relatively small excitations were measured by the sensors. The actual responses of the dam were compared to that of the finite element model to achieve a close correlation with each other. Resonant frequencies of the water dam and its vibrational modes were estimated from the model. In the next phase of the project, the research team is planning to update the geometry of the model based on laser scanning that will be conducted this year. Local anomalies (bulging areas, cracks and so on) of the water dam will be studied via an analysis of point clouds collected by the laser scanner. The fully developed model will be used in an extensive numerical study to predict the dam’s performance and its response to strong seismic events and other hazards.

  Abstract
  The paper presents recent results of an ongoing collaborative research project focused on modelling the Kurpsai water dam in Kyrgyzstan. The research team includes scientists [...]

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• Mathematical modeling and numerical results on the propagation of solitary waves on tensegrity lattices

  A. Amendola, F. Fraternali, G. Saccomandi

  eccomas2022.

  
  

  Abstract

  This work discusses the mathematical properties of the interaction potential that characterizes tensegrity mass-spring chains, and its implications in terms of the propagation of compact compression waves in such systems when impacted by a striker. Numerical simulations show evidence of the dependence of the wave form on the speed of the propagating compression pulses, which change shape when passing from the sonic to the super-sonic wave propagation regime.

  Abstract
  This work discusses the mathematical properties of the interaction potential that characterizes tensegrity mass-spring chains, and its implications in terms of the propagation [...]

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• Wear modelling in elasto-plastic wheel-rail contact problems

  A. Myśliński, A. Chudzikiewicz

  eccomas2022.

  
  

  Abstract

  The paper is concerned with the development of the numerical procedure to solve the wheel-rail contact problem and the computation of the distribution of surface flash temperatures, stresses as well as the wear evolution due to friction. The two-dimensional wheel-rail contact problem between a rigid wheel and an elasto-plastic rail lying on a rigid foundation is considered. The contact phenomenon includes Coulomb friction, frictional heat generation as well as the wear of the contacting surfaces. The displacement and stress of the rail in contact are governed by the coupled elasto-plastic and heat conductive equations. The wear depth function appears as an internal variable in the non-penetration condition updating the gap between the worn surfaces of the bodies. Moreover the dissipated energy due to friction is calculated to evaluate the loss of rail material and to determine the shape of the contacting surfaces during the wear evolution process. This contact problem is solved numerically using the finite element method as well as the operator splitting approach. The plastic flow and friction inequality conditions are reformulated as equality conditions using the nonlinear complementarity functions. The distribution of surface temperatures and stresses as well as the evolution of the shape of the contact surfaces and the wear depth are reported and discussed.

  Abstract
  The paper is concerned with the development of the numerical procedure to solve the wheel-rail contact problem and the computation of the distribution of surface flash temperatures, [...]

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• REDIM based model reduction of the decomposition of urea-water-solutions in films and droplets

  E. Berszány, M. Stein, V. Bykov, U. Maas

  eccomas2022.

  
  

  Abstract

  Selective catalytic reduction (SCR) process with urea-water solution (UWS) is often used in automotive industry to decrease emissions of nitric oxides (NO x) in the exhaust gas. In this process the urea from UWS decomposes to isocyanic acid and ammonia, where the latter is needed to increase the efficiency of the NO xreduction on the catalyst surface. Along with the advantages of using UWS several drawbacks reduce the performance of a SCR system. Incomplete decomposition of urea leads to a formation of residuals affecting the efficiency of the exhaust gas systems. Therefore, the complete decomposition of urea and homogeneous distribution of the resulting ammonia in front of the SCR catalyst represent main challenges in improving the SCR technology. In order to investigate the process of the urea decomposition a detailed chemical kinetic mechanism in the liquid phase is employed. The results are compared with a commonly used approach to model urea decomposition as an evaporation with a following decomposition reaction in the gas phase. It is shown that by using such a mechanism, the decomposition of urea and the gas phase composition with the urea decomposition products can be described more accurately. However, implementing these mechanisms in computations (in CFD approaches) requires a large amount of computational (CPU) time and memory. The method of Reaction Diffusion Manifolds (REDIMs) is implemented for the reduction of the detailed chemical kinetics in the stage of urea decomposition such that the distribution of products of the urea decomposition can be captured accurately in the gas phase with only two reduced variables instead of the 7 gas phase species of the original model.

  Abstract
  Selective catalytic reduction (SCR) process with urea-water solution (UWS) is often used in automotive industry to decrease emissions of nitric oxides (NO x) in the exhaust [...]

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• Interval field methods with local gradient control

  C. van Mierlo, M. Faes, D. Moens

  eccomas2022.

  
  

  Abstract

  This paper introduces a novel method to create an interval field based on measurement data. Such interval fields are typically used to describe a spatially distributed non-deterministic quantity, e.g., Young's modulus. The interval field is based on a number of measurement points, i.e., control points, expended throughout the domain by a set of basis functions. At the control point the non-deterministic quantity is known and bounded by an interval. However, at these measurement points information about the gradients might also be available. In addition, the non-deterministic quantity might be described better by estimating the gradients based on the other measurements. Hence, the proposed interval field method allows to incorporate this gradient information. The method is based on Inverse Distance Weighing (IDW) with an additional set of basis functions: one set of basis functions interpolates the value, and the second set of basis functions controls the gradient at the control points. The additional basis functions can be determined in two distinct ways: first, the gradients are available or can directly be measured at the control point, and second, a weighted average is taken with respect to all control points within the domain. In general, the proposed interval field provides a more versatile definition of an interval field compared to the standard implementation of inverse distance weighting. The application of the interval field is shown in a number of one-dimensional cases where a comparison with standard inverse distance weighting is made. In addition, a case study with a set of measurement data is used to illustrate the method and how different realisations are obtained.

  Abstract
  This paper introduces a novel method to create an interval field based on measurement data. Such interval fields are typically used to describe a spatially distributed non-deterministic [...]

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• A modified cohesive zone model for the simulation of mixed-mode fracture of co-consolidated thermoplastic laminates considering fiber bridging

  I. Sioutis, K. Tserpes

  eccomas2022.

  
  

  Abstract

  Fiber bridging is a mechanism that may significantly alter the fracture behavior of composite laminates, adhesively bonded laminates, welded laminates, and co-consolidated laminates. It is therefore quite important for the finite element to take that mechanism into consideration. Such models have been developed for thermosetting laminates; however, this is not the case for thermoplastic laminates and thermoplastic joints. In the present work, a numerical model based on the cohesive zone modelling (CZM) approach has been developed to simulate mixed-mode fracture of co-consolidated thermoplastic laminates by considering fiber bridging. A modified traction separation law of tri-linear form has been developed by superimposing the bi-linear behaviors of the matrix and fibers. Initially, the data from mode I (DCB) and mode II (ENF) fracture toughness tests were used to construct the R-curves of the joints in the opening and sliding directions. The aforementioned curves were embedded into the numerical models through a user-defined material subroutine developed in the LS-Dyna FE code, in order to extract the fiber bridging law directly from the simulation results. The model was used to simulate fracture of a Single-Lap-Shear (SLS) specimen in which a considerable amount of fiber bridging was observed on the fracture area. The numerical results show that the developed model presented improved accuracy in comparison to the CZM employing the bilinear traction-separation law.

  Abstract
  Fiber bridging is a mechanism that may significantly alter the fracture behavior of composite laminates, adhesively bonded laminates, welded laminates, and co-consolidated [...]

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• Phase field model for simulating fracture of ice

  R. Sondershaus, R. Müller

  eccomas2022.

  
  

  Abstract

  In the last decade, the phase field model has been established to simulate crack nucleation as well as crack propagation. In this variational approach the physically discontinuity of a crack is modeled by a continuous field variable that distinguishes between intact and broken material. The phase field model has been recently extended to viscoelastic materials in various ways, in which the rate dependent response of viscoelastic materials are taken into account. We propose a viscoelastic fracture phase field model and apply it to simulate the fracture in ice shelves. Thereby we consider the viscoelastic rheology of ice, which can be represented by a Maxwell model. The elastic response is often neglected in ice dynamic simulations but crucial for fracture mechanical studies. The numerical examples of this contribution are implemented and conducted in the finite element software FEniCS and data mimic typical situations in Antarctic and Greenland ice shelves.

  Abstract
  In the last decade, the phase field model has been established to simulate crack nucleation as well as crack propagation. In this variational approach the physically discontinuity [...]

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• Modelling of two-scale contact - Investigation of leakage in polymer seals at cryogenic temperatures

  K. Martin, J. Waimann, S. Reese

  eccomas2022.

  
  

  Abstract

  The prediction of leakage in polymer seals is still a particular challenge due to many dependencies: manufacturing inaccuracy, microparticles on the contact surface and surface asperity. Polymer seals, which are operated at cryogenic temperatures, undergo a material behaviour change at the so-called glass transition temperature. At this temperature, its behaviour changes from viscous/rubbery to glassy. There is a significant stiffening of the polymer material, which leads to a worse compensation of roughness in the contact surfaces. As a consequence the tightness of the valve may no longer be sufficiently given. The leakage through the valve is numerically investigated by a two-scale contact simulation, which is based on the concept of Representative Volume Elements, which are known in homogenization of microstructures. The deformations on the microstructure are prescribed by the macroscopic kinematics at the contact area. The mean microscopic friction coefficient is determined in Representative Contact Elements (RCE), which are node-wise linked to the macroscopic contact area. The RCEs surface texture is parameterized based on optical measurement data. As the polymer seal is operated over a wide temperature range, a fully coupled thermo-viscoelastic material model at finite strains is used to simulate the material behaviour at both scales. Due to the change from entropy to energy dominated behaviour over the glass transition temperature the model is extended to account for the transition from viscous/rubbery to glassy as the temperature is decreased. The surface asperity needs to be represented explicitly as the gap and volume between both contact surfaces and the fluid path through the seal are used to determine the leakage through the seal.

  Abstract
  The prediction of leakage in polymer seals is still a particular challenge due to many dependencies: manufacturing inaccuracy, microparticles on the contact surface and surface [...]

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