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• High-order Flux Reconstruction schemes for turbulent combustion

  R. TAMOU, J. BOHBOT, J. COATLÉVEN, V. PERRIER, Q. Tran

  ECCOMAS 2024.

  
  

  Abstract
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• A Multi-layered Integral Approach to the de-icing process

  H. Beaugendre, A. Benoit, F. Morency, M. Parisot

  ECCOMAS 2024.

  
  

  Abstract

  The modification of the shallow water icing model to handle de-icing phenomenon is the main focus of this study. As stated in the original model [1], the runback water is modeled utilizing a lubrication assumption for the water film velocity profile. A constant film temperature Tf(t,x) is then calculated under the thin-film hypothesis. Unlike the simplified icing model, the temperature field within the ice layer Tice(t,x,z) is no longer assumed to be constant. Instead, a temperature profile is utilized, enabling the generation of a static film on the wall when a heat conduction source term from a resistance is present [2]. A Temperature profile Ts(t,x,z) is also used in the static film layer if the model predicts the occurrence of this state. In the energy equation for both the solid ice and liquid portion of the static water film, transverse transfers are not considered, a 1D heat equation is then resolved. An integral approach and proper boundary conditions are used to close the problem. The validity of the integral method deteriorates as the thickness over which vertical integration is performed increases. To avoid this problem, a multi-layer approach is proposed. The thickness of the ice block is then divided into three layers of identical thickness. The purpose of this study is to offer a straightforward and robust method suitable for conducting industrial test cases. The model will first be introduced, followed by a description of the numerical approach. Subsequently, validation test cases will be conducted. Realistic de-icing scenarios will then be designed to evaluate the model [3]. Additionally, non uniform roughness effects will be examined.

  Abstract
  The modification of the shallow water icing model to handle de-icing phenomenon is the main focus of this study. As stated in the original model [1], the runback water is [...]

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• Calibration of Heston Stochastic Local Volatility Model by Numerical Solution of Nonlinear Fokker-Planck Equation

  S. Stoykov

  ECCOMAS 2024.

  
  

  Abstract

  The Fokker-Planck partial differential equation is used to compute the probability density function of the Heston stochastic local volatility model. The solution of the Fokker Planck equation is required for the calibration of the leverage function, which plays an important role in the Heston stochastic local volatility model. The current study describes a numerical method for solving the nonlinear Fokker-Planck partial differential equation. The solution is demonstrated to converge to the one generated from the implied volatility surface by comparing call option prices.

  Abstract
  The Fokker-Planck partial differential equation is used to compute the probability density function of the Heston stochastic local volatility model. The solution of the Fokker [...]

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• Immersed boundary methods for high-order discretization of the compressible Reynolds Averaged Navier-Stokes equations

  D. Lodares, J. Manzanero, E. Ferrer, E. Valero

  ECCOMAS 2024.

  
  

  Abstract

  The Immersed Boundary Method (IBM) presents clear advantages for CFD simu lation of compressible ows around complex geometries. In contrast to the standard body- tted approach, in which meshes are designed to conform to geometries, the IBM treats solid obsta cles via local modi cation of the governing equations. Popular modi cations rest on adding volumetric penalization terms to those mesh cells that are covered by immersed bodies [1] or on imposing special boundary conditions on mesh faces surrounding them [2]. In the context of the nodal Discontinuous Galerkin Spectral Element Method (DGSEM), one can also apply subcell based limiting strategies to further discretize the immersed mesh cells employing a compatible low-order method [3]. In this paper, we present a comparison between these three techniques in a high-order setting to solve compressible ows around 2D geometries using the RANS equations with the Spalart-Allmaras one-equation turbulence model. Our results show that introducing wall model-based terms is necessary for IBM formulations to yield correct RANS ow elds, and suggest that subcell-based limiting in the context of IBM can be advantageous in terms of convergence while maintaining solution accuracy.

  Abstract
  The Immersed Boundary Method (IBM) presents clear advantages for CFD simu lation of compressible ows around complex geometries. In contrast to the standard body- tted approach, [...]

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• Local Timestep Super-Time-Stepping Integration Methods Applied to Heat and Mass Transfer in Anisotropic Porous Media

  N. Dellinger, G. Dufour, X. Lamboley, L. Reboul, F. Rogier

  ECCOMAS 2024.

  
  

  Abstract

  In fire safety problems, the simulation of the thermal degradation of anisotropic porous materials is complex due to the large amplitudes of time and space scales. Degraded areas where temperature increases and gas transport occurs might be very localised, sadly reducing the overall stability of numerical solvers and increasing the computation time. This can be mitigated thanks to Super-Time-Stepping methods, which are based on the use of a multi-step explicit scheme. In this study, these methods are first presented and their advantage to handle diffusion-advection problems such as the thermal degradation of anisotropic porous materials are emphasized on a simple use case. Then, a possible acceleration of the computation by using local timestep Super-Time-Stepping methods, particularly adapted to the heterogeneous problems previously mentioned, is discussed.

  Abstract
  In fire safety problems, the simulation of the thermal degradation of anisotropic porous materials is complex due to the large amplitudes of time and space scales. Degraded [...]

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• A Multigrid preconditioner for Discontinuous Galerkin Methods Applied to Numerical Weather Prediction

  P. Birken, A. Dedner, R. Klöfkorn, J. Kasimir

  ECCOMAS 2024.

  
  

  Abstract

  High fidelity fluid simulations have important applications in science and engineer ing, examples include numerical weather prediction and simulation aided design. Discontinuous Galerkin (DG) methods are promising high order discretizations for simulating unsteady com pressible fluid flow in three dimensions. Systems arising from such discretizations are often stiff and require implicit time integration. This motivates the study of fast, parallel, low-memory solvers for the resulting algebraic equation systems. For (low order) finite volume (FV) discretizations, multigrid (MG) methods have been suc cessfully applied to steady and unsteady fluid flows. But for high order DG methods applied to f low problems, such solvers are currently lacking. The lack of efficient solvers suitable for contemporary computer architectures inhibits wider adoption of DG methods. This motivates our research to construct a Jacobian-free precondi tioner for high order DG discretizations. The preconditioner is based on a multigrid method constructed for a low order finite volume discretization defined on a subgrid of the DG mesh. Numerical experiments on atmospheric flow problems show the benefit of this approach.

  Abstract
  High fidelity fluid simulations have important applications in science and engineer ing, examples include numerical weather prediction and simulation aided design. Discontinuous [...]

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• Finite Element Simulation of a Rainfall Induced Shallow Landslide in an Experimental Hillslope with a Multiphase Porous Media Model

  M. Lazari, M. Camporese, L. Sanavia

  ECCOMAS 2024.

  
  

  Abstract

  This study presents the results of a FEM numerical simulation of a large scale physical model of a slope subjected to rainfall infiltration. The slope failure is modelled as a coupled variably saturated thermo-hydro-mechanical problem, using the Pastor-Zienkiewicz generalised plasticity model to obtain the soil’s mechanical response. Small strain and quasi static loading conditions are assumed, and plane strain conditions are adopted in the slope stability analysis. The hydraulic and mechanical parameters are calibrated based on the available experimental data. The numerical results are compared with the experimental data of the mechanical and the hydraulic responses up to failure.

  Abstract
  This study presents the results of a FEM numerical simulation of a large scale physical model of a slope subjected to rainfall infiltration. The slope failure is modelled [...]

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• Impact of saturated granular masses against rigid obstacles: the role of fluid compressibility and front inclination

  M. Zerbi, P. Marveggio, C. Prisco

  ECCOMAS 2024.

  
  

  Abstract

  In recent years, the impact of saturated granular flows against rigid obstacles has been studied by using different numerical approaches. The very low compressibility of water causes numerical instabilities when impact problems are simulated. In this work, a sensitivity analysis has been done by using a Material Point Method code to assess the influence of fluid compressibility and front inclination on numerical results. When the mass front is inclined, fluid bulk modulus does not significantly affect the solution and can be reduced to speed up the computations and reduce spurious numerical oscillations.

  Abstract
  In recent years, the impact of saturated granular flows against rigid obstacles has been studied by using different numerical approaches. The very low compressibility of water [...]

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• Studies on Effect of Interaction of Coaxial Jets on Thrust of Air-breathing Rocket

  T. Sawada, A. Oyama, Y. Maru, H. Manako

  ECCOMAS 2024.

  
  

  Abstract

  It is anticipated that the rocket-based combined cycle engine, which incorporates a rocket engine and an airbreathing engine, will offer enhanced propulsive capabilities compared to conventional rocket engines. The exhaust nozzle is a coaxial nozzle comprising a convergent divergent nozzle in the center and a convergent nozzle around it. This represents an unprecedented configuration for a rocket engine nozzle. The objective of this study is to numerically analyze the flow field near the nozzle exit and to elucidate the impact of jet interference on thrust to facilitate the detailed design of rockets. In this study, an airbreathing sounding rocket, currently under research and development at JAXA, is employed as the analysis target. The resulting calculation yielded the flow field data around the nozzle. When the central jet is over-expanded, the velocity and pressure distributions at the nozzle outlet undergo alterations due to the mutual effect of one jet pulling in the other jet. The combined thrust of the two nozzles activated simultaneously was found to be lower than the sum of the individual thrusts of the two cases in which only one of the nozzles was activated. Conversely, the thrust remains constant when the central jet is under-expanded.

  Abstract
  It is anticipated that the rocket-based combined cycle engine, which incorporates a rocket engine and an airbreathing engine, will offer enhanced propulsive capabilities compared [...]

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• Data-driven Permeability Prediction of 3D Fibrous Microstructures

  D. Natarajan, T. Schmidt, S. Cassola, M. Nuske, M. Duhovic, D. May, A. Dengel

  ECCOMAS 2024.

  
  

  Abstract

  For the manufacturing process simulation of fiber-reinforced polymer composites, f low simulations have to be performed at multiple spatial scales which govern the flow through the fiber structures. Repetitive multiscale flow simulations are computationally expensive and time-consuming. In order to speed up the multiscale simulation workflow, fast machine learning surrogate models or emulators could be used to replace one or more of the flow simulations. In this work, feature-based emulators and geometry-based emulators are developed using neural networks for predicting the permeability of 3D fibrous microstructures based on a reference dataset (doi:10.5281/zenodo.10047095). The best model achieved a mean relative error of 8.33% on the test set with a significantly faster inference time compared to a conventional simulator.

  Abstract
  For the manufacturing process simulation of fiber-reinforced polymer composites, f low simulations have to be performed at multiple spatial scales which govern the flow through [...]

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