Documents published in Scipedia

• Effect of particle-size-scaling on particle interactions in DEM-simulations of sand in the context of air pluviation

  N. Heim, S. Henke

  WCCM2024.

  
  

  Abstract

  DEM (discrete element method) is a widely used numerical simulation method, which models the behaviour of a bulk substrate based on the individual interactions of many particles. One of its possible applications is the modelling of sand behaviour in different laboratory tests, e.g., cone penetration tests [1] or direct shear tests [2]. Furthermore, DEM is specifically of interest as a modelling method for investigating air pluviation, because it models the individual inter-particle and particle-environment interactions, both friction and collisions, which determine the compaction and homogeneity of the created samples. However, one disadvantage of DEM is the relatively long computational time [3] especially with decreasing particle sizes. This makes larger particle sizes compared to reality more interesting, especially for large scale or repeating simulations. On the other hand, if the size of the chosen particles is too large, certain interactions, such as interactions with other materials and equipment, may not be simulated in a way that properly represents real behaviour. This would lead to preferring smaller sized particles, which again would lead to longer computational times. Therefore, the chosen particle size as an important aspect of DEM simulations will be discussed, as well as the effects on different simulation aspects. This includes necessary parameter calibrations, the resulting inter-particle and particle-environment interactions as well as the achieved simulation results and accuracies. Of specific interest is the largest particle size, at which accurate and realistic results concerning real-world particle interactions can be achieved. Further, the effects of graded particle sizes to better represent the sand during the pluviation process will be discussed.

  Abstract
  DEM (discrete element method) is a widely used numerical simulation method, which models the behaviour of a bulk substrate based on the individual interactions of many particles. [...]

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• Full waveform modeling in seismic exploration based on a digital geological model using spectral element method on GPU

  A. Vershinin, A. Yury, V. Levin, K. Petrovsky

  WCCM2024.

  
  

  Abstract

  The paper considers the solution of a three-dimensional problem of modeling of all types of seismic waves propagating in real geological media. The numerical algorithm based on the spectral element method (SEM). The main advantages of SEM (high order space discretization, explicit time integration scheme) are presented in comparison with the classical approach based on the finite element method (FEM). The features of the massively parallel implementation of the algorithm on modern MultiGPU systems (based on A100 GPU) using CUDA technology are considered. The efficiency of parallelization on hybrid systems with different SEM orders and parameters of the numerical time integration scheme is analyzed. The results of solving a three-dimensional problem of modeling the propagation of seismic waves in a heterogeneous geological media with faults and sharply varying properties of layers are presented. Analysis of the numerical convergence of SEM for dispersive waves of the Rayleigh type is performed. Local and non-local non-reflective boundary conditions on the artificial boundary of the computational region are considered. The 3D computational model is constructed using a detailed digital geological model built for one of the Arctic regions. It was converted to an unstructured hexahedral mesh to perform SEM calculations using CAE FIDESYS software. The model is further generalized for typical seismic-geological conditions of Western Siberia, so that on the basis of such modeling it is possible to conduct a wide range of studies on the possibilities of seismic exploration to study the main oil and gas reservoirs in this region. The solution was sought on a hexahedral mesh consisting of 5.5 mln spectral elements of the 5th order with a total number of SEM nodes 1.2 billion. The output results of full-wave modeling are stored in the SEG-Y format, suitable for all types of industrial seismic processing. The analysis of the obtained model seismograms and wave fields is carried out. The conclusion is made about the practical significance of the conducted research.

  Abstract
  The paper considers the solution of a three-dimensional problem of modeling of all types of seismic waves propagating in real geological media. The numerical algorithm based [...]

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• The method of boundary integral equations in the boundary value problems of dynamics of fluids and gases

  Y. Krashanytsia

  WCCM2024.

  
  

  Abstract

  Based on the created generalized apparatus of vector-tensor analysis, integral representations of the main dynamic and kinematic characteristics of the problem of viscous gas flow around force systems of arbitrary spatial shape are constructed. The boundary value problem of the interaction of such systems with a viscous gas flow is reduced to a system of linear, conditioned by physical boundary conditions, boundary integral equations regarding the kinematic and dynamic characteristics of the problem. It is proven that all the obtained characteristics depend on the newly obtained irrotational vector potential of the momentum, which significantly simplifies the integral representations of solutions and their numerical implementation. On the basis of the created generalized apparatus of vector-tensor analysis, integral representations of the main dynamic and kinematic characteristics of the problem of the flow of a viscous gas flow around supporting systems of satisfactory spatial form have been constructed. The boundary value problem of the interaction of such systems with a viscous gas flow is reduced to a system of linear, conditioned by physical boundary conditions, boundary integral equations regarding the kinematic and dynamic characteristics of the problem. It is proven that all the obtained characteristics depend on the newly obtained, vortex-free vector potential of the momentum, which significantly simplifies the integral representations of the solutions and their numerical implementation.

  Abstract
  Based on the created generalized apparatus of vector-tensor analysis, integral representations of the main dynamic and kinematic characteristics of the problem of viscous [...]

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• Landslide run-out simulations with depth-averaged models and integration with 3D impact analysis using the Material Point Method

  M. Fois, A. Makarim, C. FALCO, A. Larese, L. Formaggia

  WCCM2024.

  
  

  Abstract

  Landslides pose a significant threat to human safety and the well-being of communities, making them one of the most challenging natural phenomena. Their potential for catastrophic consequences, both in terms of human lives and economic impact, is a major concern. Additionally, their inherent unpredictability adds to the complexity of managing the risks associated with landslides. It is crucial to continuously monitor areas susceptible to landslides. In situ detection systems like piezometers and strain gauges play a vital role in accurately monitoring internal pressures and surface movements in the targeted areas. Simultaneously, satellite surveys contribute by offering detailed topographic and elevation data for the study area. However, relying solely on empirical monitoring is insufficient for ensuring effective management of hazardous situations, especially in terms of preventive measures. This study provides advanced simulations of mudflows and fast landslides using particle depth-averaged methods, specifically employing the Material Point Method adapted for shallow water (Depth Averaged Material Point Method). The numerical method has been parallelized and validated through benchmark tests and real-world cases. Furthermore, the investigation extends to coupling the depth-averaged formulation with a three-dimensional one in order to have a detailed description of the impact phase of the sliding material on barriers and membranes. The multidimensional approach and its validation on real cases provide a robust foundation for a more profound and accurate understanding of the behavior of mudflows and fast landslides

  Abstract
  Landslides pose a significant threat to human safety and the well-being of communities, making them one of the most challenging natural phenomena. Their potential for catastrophic [...]

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• Numerical simulation investigation on nonlinear flow characteristics of rough single fractures with different contact areas

  Y. Liang, Y. Cheng, Z. Han, C. Yan

  WCCM2024.

  
  

  Abstract

  To comprehensively understand the influence of the contact area on the flow characteristics of rough single fractures, a rough fracture surface is initially constructed using a spatial frequency domain approach. Subsequently, rough single fractures with varying contact ratios are derived by translating and displacing the fracture surface. The Navier- Stokes equation and Mass-conservation equation are solved by utilizing the laminar flow module integrated within the COMSOL software. The simulation results show that the nonlinear correlation between fluid flow velocity and pressure gradient can be described by using Forchheimer equation. Under the same flow velocity, a higher contact rate will exacerbate the nonlinear characteristics of fluid flow. In contrast to non-contact fractures, the streamlines within contact fractures exhibit increased tortuosity, accompanied by an elongation of flow pathways. Furthermore, with an expanding contact area, the complexity of the streamline pattern amplifies. The overall pressure field distinctly exhibits non-uniform characteristics, with larger pressure gradient observed within localized contact regions, consequently facilitating an increase in flow velocity.

  Abstract
  To comprehensively understand the influence of the contact area on the flow characteristics of rough single fractures, a rough fracture surface is initially constructed using [...]

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• Numerical study of fractal-tree-generated turbulence

  Y. Yin, R. Onishi, S. Watanabe, I. Segrovets

  WCCM2024.

  
  

  Abstract

  We study the aerodynamics of fractal trees by using a simulation based on the Lattice Boltzmann Method with a cumulant collision term. We have applied L-system rules to construct self-similar fractal tree models in aerodynamic computations. We found that the drag coefficient closely matches that of previous literature at high tree-height-based Reynolds numbers (ReH ≥ 60 000). A normalization process capable of collapsing turbulence intensity for various tree models is made. This process reveals that, at the same Reynolds number, different tree models exhibit the same behaviour in the turbulence intensity of their wake region. Our assessment of global and local isotropy in the turbulence generated by fractal trees reveals that the distant wake can be considered nearly locally isotropic at a high Reynolds number (ReH ≥ 60 000). Finally, the present numerical results confirm the non-equilibrium dissipation behaviour previously observed in the case of space-filling fractal square grids[2]. In the wake region, the non-dimensional dissipation rate Cϵ = constant is not valid. Instead, it is inversely proportional to the local Taylor-microscale-based Reynolds number, Cϵ ∝ 1/Reλ.

  Abstract
  We study the aerodynamics of fractal trees by using a simulation based on the Lattice Boltzmann Method with a cumulant collision term. We have applied L-system rules to construct [...]

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• Physics-informed neural network vs finite element method for modeling coupled water and solute flow in unsaturated soils

  H. Kamil, A. Soulaïmani, A. Beljadid

  WCCM2024.

  
  

  Abstract

  Accurate modeling of water infiltration and solute transport in unsaturated soils is critical for various applications. These include optimizing irrigation practices to conserve water and minimize environmental impact, as well as predicting the fate of contaminants in soil and groundwater. This study explores the application of the vanilla physics informed neural network (PINN) approach for modeling the coupled system of water flow and solute transport in unsaturated soils. We compare the performance of PINN with the Galerkin finite element method (FEM) to evaluate their effectiveness. Various techniques are implemented to improve the PINN solver, including adaptive activation functions. Numerical tests were carried out to evaluate the efficiency of the PINN solver in comparison to the FEM. The findings reveal that PINN can achieve accuracy comparable to FEM, albeit at a significantly higher computational cost during training, while maintaining fast inference times.

  Abstract
  Accurate modeling of water infiltration and solute transport in unsaturated soils is critical for various applications. These include optimizing irrigation practices to conserve [...]

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• A predictor-corrector second-order time-stepping schemes for solving water flow and solute transport in unsaturated porous media

  N. Toutlini, H. Kamil, A. Soulaïmani, A. Beljadid

  WCCM2024.

  
  

  Abstract

  The objective of this study is to numerically solve the coupled system of water flow and solute transport in unsaturated porous media using a noniterative predictor-corrector temporal scheme for the Richards equation and a semi-implicit temporal scheme for the advection dispersion equation (ADE). The standard and non-standard Galerkin finite element methods are used for spatial discretization. Three different techniques are proposed to calculate the pressure head in the Levrett equation. These techniques are different in terms of the chosen shape functions in the finite element space. The proposed schemes offer distinct advantages due to the linear nature of the resulting system, facilitating easy implementation and avoiding the issues associated with the divergence of iterative schemes. We evaluated the robustness and efficacy of the suggested methods using a computational experiment to simulate soil salinity and water flow in loamy soil. We compared it with data found in the literature. The results provide compelling evidence confirming the proposed methods’ effectiveness and stability.

  Abstract
  The objective of this study is to numerically solve the coupled system of water flow and solute transport in unsaturated porous media using a noniterative predictor-corrector [...]

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• Incompressible viscous fluid analysis around complex shapes using Isogeometric Analysis

  Y. Sakai, K. Kashiyama, H. Hasebe

  WCCM2024.

  
  

  Abstract

  This paper aims to apply the Isogeometric Analysis(IGA) to fluid-structure interaction problem in the civil engineering field. Recently, IGA has attracted much attention as an analysis method to structure with arbitrary surfaces. In this paper, IGA is applied to a twodimensional incompressible viscous flow problem as a basic study for the fluid-structure interaction analysis using IGA. The vortex induced vibration of a circular cylinder is investigated as a numerical example, and the effectiveness and validity of the coupled analysis using IGA are discussed.

  Abstract
  This paper aims to apply the Isogeometric Analysis(IGA) to fluid-structure interaction problem in the civil engineering field. Recently, IGA has attracted much attention as [...]

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• Development of traffic noise evaluation system using finite element method

  H. Miyauchi, K. Kashiyama, H. Yoshikawa

  WCCM2024.

  
  

  Abstract

  This paper presents a traffic noise evaluation system based on acoustic theory. The finite element method is employed for unsteady wave equations, which is suitable for arbitrary shapes and has excellent applicability to non-uniform materials. The 3D wave equation is employed for the governing equation and the Perfectly Matched Layer (PML) method is utilized as a treatment method for boundary condition. In order to consider multiple moving sound sources such as a traffic noise, a time-variant convolution method is introduced. The auralization method based on VR technology is also introduced to understand the noise level intuitively

  Abstract
  This paper presents a traffic noise evaluation system based on acoustic theory. The finite element method is employed for unsteady wave equations, which is suitable for arbitrary [...]

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