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See detailThe XDEM Multi-physics and Multi-scale Simulation Technology: Review on DEM-CFD Coupling, Methodology and Engineering Applications
Peters, Bernhard UL; Baniasadi, Maryam UL; Baniasadi, Mehdi UL et al

in Particuology (in press)

The XDEM multi-physics and multi-scale simulation platform roots in the Ex- tended Discrete Element Method (XDEM) and is being developed at the In- stitute of Computational Engineering at the University ... [more ▼]

The XDEM multi-physics and multi-scale simulation platform roots in the Ex- tended Discrete Element Method (XDEM) and is being developed at the In- stitute of Computational Engineering at the University of Luxembourg. The platform is an advanced multi- physics simulation technology that combines flexibility and versatility to establish the next generation of multi-physics and multi-scale simulation tools. For this purpose the simulation framework relies on coupling various predictive tools based on both an Eulerian and Lagrangian approach. Eulerian approaches represent the wide field of continuum models while the Lagrange approach is perfectly suited to characterise discrete phases. Thus, continuum models include classical simulation tools such as Computa- tional Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended configuration of the classical Discrete Element Method (DEM) addresses the discrete e.g. particulate phase. Apart from predicting the trajectories of individual particles, XDEM extends the application to estimating the thermo- dynamic state of each particle by advanced and optimised algorithms. The thermodynamic state may include temperature and species distributions due to chemical reaction and external heat sources. Hence, coupling these extended features with either CFD or FEA opens up a wide range of applications as diverse as pharmaceutical industry e.g. drug production, agriculture food and processing industry, mining, construction and agricultural machinery, metals manufacturing, energy production and systems biology. [less ▲]

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See detailA Dual-Grid Multiscale Approach to CFD-DEM Couplings for Multiphase Flow
Pozzetti, Gabriele UL

Doctoral thesis (2018)

This thesis focuses on a novel dual-grid multiscale approach to CFD- DEM1 couplings, proposes its advantages in terms of numerical proper- ties and performance, and provides examples of engineering ... [more ▼]

This thesis focuses on a novel dual-grid multiscale approach to CFD- DEM1 couplings, proposes its advantages in terms of numerical proper- ties and performance, and provides examples of engineering applications that can benefit from it. In recent years, CFD-DEM couplings are be- coming a more and more adopted solution for the numerical simulation of particle-laden flows. In particular, couplings based on the volume av- eraging technique have become a standard for numerical simulations in chemical and process engineering. Furthermore, they are rapidly spread- ing to civil, geotechnical and mechanical applications due to their ability in dealing with arbitrarily complex mixtures of continuum and granular media. Despite the several advantages that these Eulerian-Lagrangian cou- plings provide, their rigorous application to complex scenarios is currently limited by two main factors. First, the computational traceability of the solutions can become problematic due to the lack of a general theory on the subject. In particular, grid-convergence studies for the solution of the continuous phases are often not feasible due to the averaging procedure that imposes limitations on the grid structure and refinement. Second, the parallel implementation of these numerical schemes holds important disadvantages in terms of memory consumption and inter-physics com- munication load. These disadvantages are significantly limiting the ex- tension of these approaches to large-scale scenarios. This thesis collects some of the most significant works published in the last years on a novel approach that allows solving the two above- mentioned problems, and, therefore, tackling more complex and expen- sive scenarios. I refer to this approach as dual-grid multiscale approach for CFD-DEM couplings. It consists in using two different computational grids, one for the coupling between continuum and discrete entities and one for the solution of the so-obtained continuum equations. The two grids, i.e. the two problems, are in this way resolved on two different scales. The first scale or “bulk” scale is chosen to optimize the averag- ing operation. At this length-scale, the discrete entities are considered as zero-dimensional, and interact with the fluid with local exchanges of momentum, mass, and energy. The second scale or “fluid-fine” scale is identified as the one at which a unique solution for the averaged equa- tions can be provided. In practice, this is chosen as the one at which the solution of the fluid equations becomes grid-independent. An inter-scale communication is adopted by interpolating fields from the fluid-fine scale to the bulk one and vice-versa. The theoretical description of the method is first provided with par- ticular reference to the DEM-VOF coupling. Even in its simplest version, the multiscale approach is shown to generate grid-convergent solutions and significantly higher accuracy than a standard CFD-DEM coupling. This shows how the new approach is able to overcome the first main limitation described above. Then, an optimized parallel implementation of the method is pro- posed to show how this multiscale approach can provide significant ben- efits also for what concerns the execution time. Technically, this is made possible by moving the communication cost of the coupling from the inter-physics communication that characterized the standard CFD-DEM couplings to an optimized inter-scale communication routine. This en- ables the method to overcome a major bottleneck of the parallel execution of CFD-DEM couplings and therefore the second main limitation of those schemes. Finally, the dual-grid multiscale method is applied to approach in- dustrially relevant problems that were till now out-of-reach for standard CFD-DEM couplings, proving how this technique can have direct real- case application and produce immediate benefits for practitioners willing to adopt it. [less ▲]

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See detailA co-located partitions strategy for parallel CFD-DEM couplings
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

in Advanced Powder Technology (2018)

In this work, a new partition-collocation strategy for the parallel execution of CFD–DEM couplings is investigated. Having a good parallel performance is a key issue for an Eulerian-Lagrangian software ... [more ▼]

In this work, a new partition-collocation strategy for the parallel execution of CFD–DEM couplings is investigated. Having a good parallel performance is a key issue for an Eulerian-Lagrangian software that aims to be applied to solve industrially significant problems, as the computational cost of these couplings is one of their main drawback. The approach presented here consists in co-locating the overlapping parts of the simulation domain of each software on the same MPI process, in order to reduce the cost of the data exchanges. It is shown how this strategy allows reducing memory consumption and inter-process communication between CFD and DEM to a minimum and therefore to overcome an important parallelization bottleneck identified in the literature. Three benchmarks are proposed to assess the consistency and scalability of this approach. A coupled execution on 280 cores shows that less than 0.1% of the time is used to perform inter-physics data exchange. [less ▲]

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See detailParallel Coupling of CFD-DEM simulations
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

Presentation (2018, August)

Eulerian-Lagrangian couplings are nowadays widely used to address engineering and technical problems. In particular, CFD-DEM couplings have been successfully applied to study several configurations ... [more ▼]

Eulerian-Lagrangian couplings are nowadays widely used to address engineering and technical problems. In particular, CFD-DEM couplings have been successfully applied to study several configurations ranging from mechanical, to chemical and environmental engineering. However, such simulations are normally very computationally intensive, and the execution time represents a major issue for the applicability of this numerical approach to complex scenarios. With this work, we introduce a novel coupling approach aiming at improving the performance of the parallel CFD-DEM simulations. This strategy relies on two points. First, we propose a new partition-collocation strategy for the parallel execution of CFD–DEM couplings, which can considerably reduce the amount of inter-process communication between the CFD and DEM parts. However, this strategy imposes some alignment constraints on the CFD mesh. Secondly, we adopt a dual-grid multiscale scheme for the CFD-DEM coupling, that is known to offer better numerical properties, and that allows us to obtain more flexibility on the domain partitioning overcoming the alignment constraints. We assess the correctness and performance of our approach on elementary benchmarks and at a large scale with a realistic test-case. The results show a significant performance improvement compared to other state-of-art CFD-DEM couplings presented in the literature. [less ▲]

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See detailA Multiscale DEM-VOF Method for the simulation of three-phase flows
Pozzetti, Gabriele UL; Peters, Bernhard UL

in International Journal of Multiphase Flow (2018), 99

A novel multiscale approach for three-phase flows is presented. The goal of the proposed method is to solve arbitrary three-phase flow configurations in a computationally efficient way, and in particular ... [more ▼]

A novel multiscale approach for three-phase flows is presented. The goal of the proposed method is to solve arbitrary three-phase flow configurations in a computationally efficient way, and in particular taking into account the effects of different length scales while sharply reducing the computational burden. This is particularly important in chemical, environmental, and process engineering, where large-scale quantities are normally of interest, but small-scale dynamics cannot be neglected. The method is based on the definition of two different length scales: the bulk scale, and the fluid fine scale. A dual-grid approach is adopted in order to resolve the bulk scale with information from the fluid fine scale. It is shown that the described method succeeds in delivering more accuracy than a standard approach based on the volume averaging technique, still, it remains suitable for the solution of real interest problems. The method is shown to successfully satisfy experimental results presented in the literature. Examples of three-phase flows simulations are provided to show how the proposed numerical approach can describe the physics of particle-laden, free surface flows with competitive computational cost. It is shown how the proposed method can naturally extend the DEM-VOF method to the presence of complex interface dynamics. [less ▲]

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See detailA parallel dual-grid multiscale approach to CFD-DEM couplings
Pozzetti, Gabriele UL; Jasak, Hrvoje; Besseron, Xavier UL et al

E-print/Working paper (2018)

In this work, a new parallel dual-grid multiscale approach for CFD-DEM couplings is investigated. Dual- grid multiscale CFD-DEM couplings have been recently developed and successfully adopted in different ... [more ▼]

In this work, a new parallel dual-grid multiscale approach for CFD-DEM couplings is investigated. Dual- grid multiscale CFD-DEM couplings have been recently developed and successfully adopted in different applications still, an efficient parallelization for such a numerical method represents an open issue. Despite its ability to provide grid convergent solutions and more accurate results than standard CFD-DEM couplings, this young numerical method requires good parallel performances in order to be applied to large-scale problems and, therefore, extend its range of application. The parallelization strategy here proposed aims to take advantage of the enhanced complexity of a dual-grid coupling to gain more flexibility in the domain partitioning while keeping a low inter-process communication cost. In particular, it allows avoiding inter- process communication between CFD and DEM software and still allows adopting complex partitioning strategies thanks to an optimized grid-based communication. It is shown how the parallelized multiscale coupling holds all its natural advantages over a mono-scale coupling and can also have better parallel performance. Three benchmark cases are presented to assess the accuracy and performance of the strategy. It is shown how the proposed method allows maintaining good parallel performance when operated over 1000 processes. [less ▲]

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See detailA Numerical approach for the evaluation of particle-induced erosion in an Abrasive Waterjet focusing tube
Pozzetti, Gabriele UL; Peters, Bernhard UL

in Powder Technology (2018)

In this work, a numerical approach to study erosion phenomena inside a focusing tube for Abrasive Water Jet (AWJ) is presented. The goal of this approach is to capture the erosive action of the particle ... [more ▼]

In this work, a numerical approach to study erosion phenomena inside a focusing tube for Abrasive Water Jet (AWJ) is presented. The goal of this approach is to capture the erosive action of the particle-laden flow developing inside the focusing tube as a result of cumulated impact phenomena. This is fundamental in the research and development of this sector in order to optimize cost and reliability of the AWJ system. With this purpose, a multiscale algorithm for CFD-DEM is used in combination with erosion models presented in the literature so to retrieve erosion profiles comparable to the one obtained by the most common experiments in this field. The approach is shown to provide insight into the process of wear development as the identification of areas characterized by brittle and cut phenomena. Preliminary parametric studies on the influence of impact models and particle diameters are proposed to show the potentialities of the method in describing the physics of the nozzle. [less ▲]

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See detailA Parallel Multiscale DEM-VOF Method For Large-Scale Simulations Of Three-Phase Flows
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

in Proceedings of ECCM-ECFD 2018 (2018)

A parallel dual-grid multiscale DEM-VOF coupling is here investigated. Dual- grid multiscale couplings have been recently used to address different engineering problems involving the interaction between ... [more ▼]

A parallel dual-grid multiscale DEM-VOF coupling is here investigated. Dual- grid multiscale couplings have been recently used to address different engineering problems involving the interaction between granular phases and complex fluid flows. Nevertheless, previous studies did not focus on the parallel performance of such a coupling and were, therefore, limited to relatively small applications. In this contribution, we propose an insight into the performance of the dual-grid multiscale DEM-VOF method for three- phase flows when operated in parallel. In particular,we focus on a famous benchmark case for three-phase flows and assess the influence of the partitioning algorithm on the scalability of the dual-grid algorithm. [less ▲]

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See detailOn the performance of an overlapping-domain parallelization strategy for Eulerian-Lagrangian Multiphysics software
Pozzetti, Gabriele UL; Besseron, Xavier UL; Rousset, Alban UL et al

in AIP Conference Proceedings ICNAAM 2017 (2017, September)

In this work, a strategy for the parallelization of a two-way CFD-DEM coupling is investigated. It consists on adopting balanced overlapping partitions for the CFD and the DEM domains, that aims to reduce ... [more ▼]

In this work, a strategy for the parallelization of a two-way CFD-DEM coupling is investigated. It consists on adopting balanced overlapping partitions for the CFD and the DEM domains, that aims to reduce the memory consumption and inter-process communication between CFD and DEM. Two benchmarks are proposed to assess the consistency and scalability of this approach, coupled execution on 252 cores shows that less than 1\% of time is used to perform inter-physics data exchange. [less ▲]

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See detailFlow characteristics of metallic powder grains for additive manufacturing
Peters, Bernhard UL; Pozzetti, Gabriele UL

in EPJ Web of Conferences (2017), 13001

Directed energy deposition technologies for additive manufacturing such as laser selective melting (SLM) or electron beam melting (EBM) is a fast growing technique mainly due to its flexibility in product ... [more ▼]

Directed energy deposition technologies for additive manufacturing such as laser selective melting (SLM) or electron beam melting (EBM) is a fast growing technique mainly due to its flexibility in product de- sign. However, the process is a complex interaction of multi-physics on multiple length scales that are still not entirely understood. A particular challenging task are the flow characteristics of metallic powder ejected as jets from a nozzle and shielded by an inert turbulent gas flow. Therefore, the objective is to describe numerically the complex interaction between turbulent flow and powder grains. In order to include both several physical processes and length scales an Euler-Lagrange technology is applied. Within this framework powder is treated by the Discrete-Element-Method, while gas flow is described by Euler approaches as found in classical Compu- tational Fluid Dynamics (CFD). The described method succeeded in delivering more accuracy and consistency than a standard approach based on the volume averaging technique and therefore, is suited for the solution of problems within an engineering framework. [less ▲]

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See detailOn the choice of a phase interchange strategy for a multiscale DEM-VOF Method
Pozzetti, Gabriele UL; Peters, Bernhard UL

in AIP Conference Proceedings (2017), 1863

In this work a novel Multiscale DEM-VOF method is adopted to study three phase flows. It consists in solving the fluid momentum, mass conservation and the phase advection at a different scale with respect ... [more ▼]

In this work a novel Multiscale DEM-VOF method is adopted to study three phase flows. It consists in solving the fluid momentum, mass conservation and the phase advection at a different scale with respect to the fluid-particle coupling problem. This allows the VOF scheme to resolve smaller fluid structures than a classic DEM-VOF method, and opens the possibility of adopting different volume interchange techniques. Two different volume interchange techniques are here described and compared with reference to high and low particle concentration scenarios. Considerations about the respective computational costs are also proposed. [less ▲]

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See detailLES-VOF SIMULATIONS OF A PURE WATER JET DEVELOPING INSIDE AN AWJC NOZZLE: PRELIMINARY OBSERVATIONS AND GUIDELINES
Pozzetti, Gabriele UL; Peters, Bernhard UL

in 2017 WJTA-IMCA Conference Proceedings (2017)

In this work, a numerical approach to predict the behavior of a pure water jet developing inside a nozzle for Abrasive Water Jet Cutting (AWJC) is investigated. In a standard AWJC configuration, the water ... [more ▼]

In this work, a numerical approach to predict the behavior of a pure water jet developing inside a nozzle for Abrasive Water Jet Cutting (AWJC) is investigated. In a standard AWJC configuration, the water jet carries the major energy content of the entire system, and is responsible for accelerating abrasive particles that will perform the cutting action of hard materials. Therefore an accurate simulation of a pure water jet can bring significant insight on the overall AWJC process. Capturing the behavior of a multiphase high-speed flow in a complex geometry is however particularly challenging. In this work, we adopt a combined approach based on the Volume of Fluid (VOF) and Large Eddy Simulation (LES) techniques in order to respectively capture the water/air interface and to model turbulent structures of the flow. The aim of this contribution is to investigate how the two techniques apply to the specific problem, and to offer general guidelines for practitioners willing to adopt them. Costs considerations will be then presented with particular reference to the usage of the OpenFOAM® environment. The reported results are meant to provide guidance for AWJ applications and future developments of AWJ nozzles. [less ▲]

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See detailEvaluating Erosion Patterns in an abrasive water jet cutting nozzle using XDEM
Pozzetti, Gabriele UL; Peters, Bernhard UL

in Advances in Powder Metallurgy & Particulate Materials (2017)

The objective of this work is to analyze particle-induced erosion within a nozzle for abrasive water jet cutting, through a Euler-Lagrange approach. In an abrasive water jet cutting device a high-speed ... [more ▼]

The objective of this work is to analyze particle-induced erosion within a nozzle for abrasive water jet cutting, through a Euler-Lagrange approach. In an abrasive water jet cutting device a high-speed water jet is used to accelerate abrasive particles forming a turbulent mixture of water, entrained air and abrasive powders traveling at hundreds of meters per second. The focusing tube represents a key component, whose primary scope is to focus and stabilize the flow forming in the mixing chamber, in order to ensure optimal cutting performances of the device. Nevertheless, this nozzle often happens to be the first target of the erosive action of the flow. This phenomenon significantly shortens the operational life of a nozzle. The numerical approach proposed in this work aims to provide an insight to this very fast and disruptive phenomena that are difficult and expensive to be captured by purely experimental studies. [less ▲]

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See detailMultiscale-multiphysics approaches for engineering applications
Pozzetti, Gabriele UL; Peters, Bernhard UL

in AIP Conference Proceedings (2017), 1863(1), 180001

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See detailON THE INFLUENCE OF DIFFERENT MAPPING TECHNIQUES FOR A MULTISCALE APPROACH TO TURBULENT THREE-PHASE FLOWS
Pozzetti, Gabriele UL; Peters, Bernhard UL

Scientific Conference (2016, June 06)

In this work we investigate a multiscale approach for high Stokes number, turbulent three phase flows. It is widely proven that a straightforward application of Galerkin's method to problems characterized ... [more ▼]

In this work we investigate a multiscale approach for high Stokes number, turbulent three phase flows. It is widely proven that a straightforward application of Galerkin's method to problems characterized by multiscale phenomena does not generally lead to robust numerical solutions. In this optic, multiscale methods are commonly adopted in order to provide solutions for complex problems in an highly efficient way. In certain problems it is convenient to identify multiple scales (more than 2), each characterized by its own characteristic spatial and temporal length. For this kind of problems a possible approach consists in completely resolving the coarse scales, partially resolving the middle scales, while analytically modeling the smallest. In turbulent three phase flows with high Stokes number, those can be identified respectively as the particle characteristic scale, the interface dynamic scale, and the turbulent fine scale. The coarse scale is here resolved through an Eulerian-Lagrangian approach that enables us to track the particle motion in a Lagrangian way. We partially resolve the middle-scale through the usage of a supporting domain where semi local variables are resolved. The solution of the middle-scale is based on the Volume of Fluid (VOF) technique in order to capture the dynamic interface, while turbulent phenomena are solved with a Large Eddy Simulation (LES) approach. The coarse-scale domain and the middle-scale domain must exchange informations and this process is obtained by mapping variables between the two fields. We will here show how the choice of the mapping technique largely affect the solution in therms of both accuracy and efficiency. A thoughtful study about the optimal mapping strategy could therefore be extremely beneficial in order to discover the most suitable scale-linking technique. The aim of this work is to investigate the effect of the adopted mapping technique on the resolved scale. Simulations with different Reynolds and Stokes number are proposed and compared, and conclusions about the consistency of the mapping technique are drawn. [less ▲]

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See detailA DEM-LES-VOF METHOD FOR TURBULENT THREE PHASE FLOWS
Pozzetti, Gabriele UL; Peters, Bernhard UL

Scientific Conference (2016, May 26)

In this work a robust Computational Fluid Dynamic (CFD) - Discrete Element Method(DEM) coupling that can predict free-surface, turbulent flows is presented. A correct prediction of multiphase turbulent ... [more ▼]

In this work a robust Computational Fluid Dynamic (CFD) - Discrete Element Method(DEM) coupling that can predict free-surface, turbulent flows is presented. A correct prediction of multiphase turbulent flows should ideally be able to capture the discrete dynamics of a dispersed phase (solid particles), and at the same time to take into account the evolution of possible fluid-dynamic instabilities. In this optic a CFD-DEM approach seems promising as it is able to combine the well developed CFD techniques for the study of free-surface flows with the accuracy of the Discrete Particle Method(DPM). A key point of the CFD-DEM method is the coupling between the discrete and the continuous phases. In particular the volume replacement between phases, and the interaction between the discrete phase and the continuous interface must be taken into account in order to perform accurate three phase simulations. In this work two different approaches to simulate the volume replacement between phases are presented and compared within a four way coupling with a Large Eddy Simulation(LES)-Volume Of Fluid(VOF) solver. The four-way coupled equations for the solid and the fluids are then presented, and some test cases provided in order to evaluate the accuracy of the new solver. Particular emphasis is posed to study the effects of the coupling on the interface dynamics and stability. The continuous two-phase solver used for the simulations is based on the OpenFoam® architecture, while the discrete phase solver is built on the XDEM code. [less ▲]

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See detailA PRELIMINARY STUDY ON THE STABILITY OF PARTICLE LADEN JETS THROUGH A FULLY COUPLED CFD-DEM SOLVER
Peters, Bernhard UL; Pozzetti, Gabriele UL

Poster (2016, May 22)

Jets are widely used in engineering applications. In material machinery, hydro-transportation systems as well as in chemical industry it is common to deal with a dispersed solid phase interacting with the ... [more ▼]

Jets are widely used in engineering applications. In material machinery, hydro-transportation systems as well as in chemical industry it is common to deal with a dispersed solid phase interacting with the jet, and therefore creating a so-called slurry-jet or particle-laden jet. The stability of a jet is a key issue for many of these processes, still the underlying physics of this turbulent multiphase flow is highly complicated. Conventional CFD approaches have been proven satisfying for the study of the stability of two-phase jets. When a solid dispersed phase is present in the system, the stability problem gets more complicated and dependent on the solid phase dynamic. A possible solution for the problem is to extend the CFD solver capability through a correct coupling with a DEM solver. In this work a preliminary investigation on the potentialities of this kind of approach is presented and compared with a pure CFD approach. In particular the effect of the presence of differently sized particles in the jet is outlined and the influence of particle properties and concentration is investigated. Finally some considerations about the computational cost of different methods are proposed. The fluid phases are solved through an Eulerian finite volume (FV) multiphase solver based on the OpenFoam® libraries, and coupled with the XDEM code in order to treat the dispersed phase in a Lagrangian way. [less ▲]

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See detailBerechnung des Transportes von Treibgut bei Hochwasser
Peters, Bernhard UL; Pozzetti, Gabriele UL; Liao, Yu-Chung UL

in 39. DRESDNER WASSERBAUKOLLOQUIUM (2016)

Hochwasser hervorgerufen durch natürliche Ursachen wie Schneeschmelze oder durch bauliche Maßnahmen wie Flussbegradigung verursacht häufig eine Flutkatastrophe mit verheerenden Überschwemmungen. Zu den ... [more ▼]

Hochwasser hervorgerufen durch natürliche Ursachen wie Schneeschmelze oder durch bauliche Maßnahmen wie Flussbegradigung verursacht häufig eine Flutkatastrophe mit verheerenden Überschwemmungen. Zu den schon katastrophalen Folgen von Hochwasser addieren sich häufig noch die Schäden von gefährliche Treibgut, das mit den Fluten mitgerissen wird und unter Umständen über weite Strecken transportiert wird. Mitgerissenes Treibgut kann zur Verklausung von Brücken führen oder auch Bauwerke zerstören. Um die Folgen eines Hochwassers einschließlich Transport von Treibgut abschätzen zu können, sind numerische Werkzeuge eine adäquate Ergänzung zu experimentellen Methoden, die oft mit einem sehr hohen Aufwand verbunden sind. Deshalb wird im vorliegenden Beitrag eine neue und innovative numerischer Ansatz vorgestellt, der den Transport von Treibgut bei Hochwasser aber auch bei Normalwasser beschreibt. Dazu werden die beiden numerischen Methoden beruhend auf einem diskreten und kontinuierlichem Ansatz gekoppelt. Letzterer beinhaltet die Euler Methoden, mit denen die Strömung des Wassers im Rahmen von bewährten Rechenmethoden der Computational Fluid Dynamik (CFD) bestimmt wird. Treibgut wird diskret betrachtet, in dem es mit der Diskreten Element Methode (DEM) beschreiben wird. Damit kann sowohl jedes einzelne Element des Treibgutes berücksichtigt werden als auch seine Eigenschaften wie Größe, Form und Gewicht. Innerhalb dieses Ansatzes können die Kontaktkräfte zwischen den einzelnen Elementen des Treibgutes berechnet werden, mit denen sich Geschwindigkeit, Position und Orientierung des Treibgutes bestimmen lassen. Zusätzlich wird über eine Kopplung zur fluiden Phase der Einfluss sowohl der Wassergeschwindigkeit als des Auftriebs mit berücksichtigt. [less ▲]

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See detailA preliminary investigation of the growth of an aneurysm with a multiscale monolithic Fluid-Structure interaction solver
Cerroni, D.; Manservisi, S.; Pozzetti, Gabriele UL

in Journal of Physics: Conference Series (2015), 655(1), 012050

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction ... [more ▼]

In this work we investigate the potentialities of multi-scale engineering techniques to approach complex problems related to biomedical and biological fields. In particular we study the interaction between blood and blood vessel focusing on the presence of an aneurysm. The study of each component of the cardiovascular system is very difficult due to the fact that the movement of the fluid and solid is determined by the rest of system through dynamical boundary conditions. The use of multi-scale techniques allows us to investigate the effect of the whole loop on the aneurysm dynamic. A three-dimensional fluid-structure interaction model for the aneurysm is developed and coupled to a mono-dimensional one for the remaining part of the cardiovascular system, where a point zero-dimensional model for the heart is provided. In this manner it is possible to achieve rigorous and quantitative investigations of the cardiovascular disease without loosing the system dynamic. In order to study this biomedical problem we use a monolithic fluid-structure interaction (FSI) model where the fluid and solid equations are solved together. The use of a monolithic solver allows us to handle the convergence issues caused by large deformations. By using this monolithic approach different solid and fluid regions are treated as a single continuum and the interface conditions are automatically taken into account. In this way the iterative process characteristic of the commonly used segregated approach, it is not needed any more. [less ▲]

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