214 research outputs found

    Cylindrical smoothed particle hydrodynamics simulations of water entry

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    This paper presents a smoothed particle hydrodynamics (SPH) modeling technique based on the cylindrical coordinates for axisymmetrical hydrodynamic applications, thus to avoid a full three-dimensional (3D) numerical scheme as required in the Cartesian coordinates. In this model, the governing equations are solved in an axisymmetric form and the SPH approximations are modified into a two-dimensional cylindrical space. The proposed SPH model is first validated by a dam-break flow induced by the collapse of a cylindrical column of water with different water height to semi-base ratios. Then, the model is used to two benchmark water entry problems, i.e., cylindrical disk and circular sphere entry. In both cases, the model results are favorably compared with the experimental data. The convergence of model is demonstrated by comparing with the different particle resolutions. Besides, the accuracy and efficiency of the present cylindrical SPH are also compared with a fully 3D SPH computation. Extensive discussions are made on the water surface, velocity, and pressure fields to demonstrate the robust modeling results of the cylindrical SPH

    Hybrid Thermo-Mechanical Contact Algorithm for 3D SPH-FEM Multi-Physics Simulations

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    Numerical simulation of complex industrial processes has become increasingly ommon in recent years. Depending on the nature of the industrial application, multiple types of physical phenomena may need to be considered as well as the interaction of multiple disjoint bodies. This paper is focused on industrial applications with large plastic deformation. Such processes are typically not well treated by finite element (FE) methods. For this reason, the smoothed particle hydrodynamics method (SPH) is used. In this work, we introduce a robust and straightforward thermo-mechanical contact algorithm for multi-physics SPH simulations in 3D

    Discrete-continuum hybrid modelling of flowing and static regimes

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    Bulk handling, transport and processing of granular materials and powders are fundamental operations in a wide range of industrial processes and geophysical phenomena. Particulate materials, which can be found in nature, are usually characterized by grain size which can range across several scales: from nanometre to the order of metre. Depending on the volume fraction and shear strain conditions, granular materials can have different behaviours and often can be expressed as a new state of matter with properties of solids, liquids and gases. For the above reasons both the experimental and the numerical analysis of granular media is still a difficult task and the prediction of their dynamic behaviour still represents nowadays an important challenge. The main goal of the current thesis is the development of a numerical strategy with the objective of studying the macroscopic behaviour of dry granular flows in quasi-static and dense flow regime. The problem is defined in a continuum mechanics framework and the balance laws, which govern the behaviour of a solid body, are solved by using a Lagrangian formalism. The Material Point Method (MPM), a particle-based method, is chosen due to its features which make it very suitable for the solution of large deformation problems involving complex history-dependent constitutive laws. An irreducible formulation using a Mohr-Coulomb constitutive law, which takes into account geometric non-linearities, is implemented within the MPM framework. The numerical strategy is verified and validated against several benchmark tests and experimental results, available in the literature. Further, a mixed formulation is implemented for the solution of granular flows that undergo undrained conditions. Finally, the developed MPM strategy is used and tested against the experimental study performed for the characterization of the flowability of several types of sucrose. The capabilities and limitations of this numerical strategy are observed and discussed and the bases for future research are outlined.El manejo, el transporte y el procesamiento de materiales granulares y polvo son operaciones fundamentales en una amplia gama de procesos industriales y de fenómenos geofísicos. Los materiales particulados, que pueden ser encontrados en la naturaleza, generalmente están caracterizados por el tamaño del grano, que puede variar entre varios órdenes de magnitud: desde el nanómetro hasta el orden de los metros. En función de las condiciones de fracción volumétrica y de deformación de cortante, los materiales granulares pueden tener un comportamiento diferente y a menudo pueden expresarse como un nuevo estado de materia con propiedades de sólidos, de líquidos y de gases. A causa de las observaciones antes mencionadas, tanto el análisis experimental como la simulación numérica de medios granulares es aún una tarea compleja y la predicción de su comportamiento dinámico representa aun hoy día un desafío muy importante. El principal objetivo de esta tesis es el desarrollo de una estrategia numérica con la finalidad de estudiar el comportamiento macroscópico de los flujos de medios granulares secos en régimen cuasiestático y en régimen dinámico. El problema está definido en el contexto de la mecánica de medios continuos y las leyes de equilibrio, que gobiernan el comportamiento del cuerpo sólido, y están resueltas mediante un formalismo Lagrangiano. El Metodo de los Puntos Materiales (MPM), método basado en el concepto de discretización del cuerpo sólido en partículas, está elegido por sus características que lo convierten en una técnica apropiada para resolver problemas de grandes deformaciones donde se tienen que utilizar complejas leyes constitutivas. En el marco del MPM está implementada una formulación irreducible que usa una ley constitutiva de Mohr-Coulomb y que tiene en cuenta no-linealidades geométricas. La estrategia numérica está verificada y validada con respecto a tests de referencia y resultados experimentales disponibles en la literatura. Además, se ha implementado una formulación mixta para resolver casos de flujo granular en condiciones no drenadas. Por último, la estrategia MPM desarrollada está utilizada y evaluada con respecto a un estudio experimental realizado para la caracterización de la fluidez de diferentes tipologías de azúcar. También se presentan unas observaciones y discusión sobre las capacidades y las limitaciones de esta herramienta numérica y se describen las bases de una investigación futura.Postprint (published version

    Discrete-continuum hybrid modelling of flowing and static regimes

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    Bulk handling, transport and processing of granular materials and powders are fundamental operations in a wide range of industrial processes and geophysical phenomena. Particulate materials, which can be found in nature, are usually characterized by grain size which can range across several scales: from nanometre to the order of metre. Depending on the volume fraction and shear strain conditions, granular materials can have different behaviours and often can be expressed as a new state of matter with properties of solids, liquids and gases. For the above reasons both the experimental and the numerical analysis of granular media is still a difficult task and the prediction of their dynamic behaviour still represents nowadays an important challenge. The main goal of the current thesis is the development of a numerical strategy with the objective of studying the macroscopic behaviour of dry granular flows in quasi-static and dense flow regime. The problem is defined in a continuum mechanics framework and the balance laws, which govern the behaviour of a solid body, are solved by using a Lagrangian formalism. The Material Point Method (MPM), a particle-based method, is chosen due to its features which make it very suitable for the solution of large deformation problems involving complex history-dependent constitutive laws. An irreducible formulation using a Mohr-Coulomb constitutive law, which takes into account geometric non-linearities, is implemented within the MPM framework. The numerical strategy is verified and validated against several benchmark tests and experimental results, available in the literature. Further, a mixed formulation is implemented for the solution of granular flows that undergo undrained conditions. Finally, the developed MPM strategy is used and tested against the experimental study performed for the characterization of the flowability of several types of sucrose. The capabilities and limitations of this numerical strategy are observed and discussed and the bases for future research are outlined.El manejo, el transporte y el procesamiento de materiales granulares y polvo son operaciones fundamentales en una amplia gama de procesos industriales y de fenómenos geofísicos. Los materiales particulados, que pueden ser encontrados en la naturaleza, generalmente están caracterizados por el tamaño del grano, que puede variar entre varios órdenes de magnitud: desde el nanómetro hasta el orden de los metros. En función de las condiciones de fracción volumétrica y de deformación de cortante, los materiales granulares pueden tener un comportamiento diferente y a menudo pueden expresarse como un nuevo estado de materia con propiedades de sólidos, de líquidos y de gases. A causa de las observaciones antes mencionadas, tanto el análisis experimental como la simulación numérica de medios granulares es aún una tarea compleja y la predicción de su comportamiento dinámico representa aun hoy día un desafío muy importante. El principal objetivo de esta tesis es el desarrollo de una estrategia numérica con la finalidad de estudiar el comportamiento macroscópico de los flujos de medios granulares secos en régimen cuasiestático y en régimen dinámico. El problema está definido en el contexto de la mecánica de medios continuos y las leyes de equilibrio, que gobiernan el comportamiento del cuerpo sólido, y están resueltas mediante un formalismo Lagrangiano. El Metodo de los Puntos Materiales (MPM), método basado en el concepto de discretización del cuerpo sólido en partículas, está elegido por sus características que lo convierten en una técnica apropiada para resolver problemas de grandes deformaciones donde se tienen que utilizar complejas leyes constitutivas. En el marco del MPM está implementada una formulación irreducible que usa una ley constitutiva de Mohr-Coulomb y que tiene en cuenta no-linealidades geométricas. La estrategia numérica está verificada y validada con respecto a tests de referencia y resultados experimentales disponibles en la literatura. Además, se ha implementado una formulación mixta para resolver casos de flujo granular en condiciones no drenadas. Por último, la estrategia MPM desarrollada está utilizada y evaluada con respecto a un estudio experimental realizado para la caracterización de la fluidez de diferentes tipologías de azúcar. También se presentan unas observaciones y discusión sobre las capacidades y las limitaciones de esta herramienta numérica y se describen las bases de una investigación futura

    LOQUAT: an open-source GPU-accelerated SPH solver for geotechnical modeling

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    Smoothed particle hydrodynamics (SPH) is a meshless method gaining popularity recently in geotechnical modeling. It is suitable to solve problems involving large deformation, free-surface, cracking and fragmentation. To promote the research and application of SPH in geotechnical engineering, we present LOQUAT, an open-source three-dimensional GPU accelerated SPH solver. LOQUAT employs the standard SPH formulations for solids with two geomechnical constitutive models which are the Drucker–Prager model and a hypoplastic model. Three stabilization techniques, namely, artificial viscosity, artificial pressure and stress regularization are included. A generalized boundary particle method is presented to model static and moving boundaries with arbitrary geometry. LOQUAT employs GPU acceleration technique to greatly increase the computational efficiency. Numerical examples show that the solver is convergent, stable and highly efficient. With a mainstream GPU, it can simulate large scale problems with tens of millions of particles, and easily performs more than one thousand times faster than serial CPU code

    A SPH approach for large deformation analysis with hypoplastic constitutive model

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    A hypoplastic constitutive model is implemented in a smoothed particle hydrodynamics code for the first time. An improved wall boundary treatment is presented for better performance. The proposed approach is first validated by comparing the numerical results with the analytical solutions for oedometer test. Two more problems involving large deformation, i.e., the collapse of sand between two parallel plates and the failure of a homogeneous slope, are analyzed to demonstrate the performance of the proposed method

    Numerical analysis of the post-fracture response of laminated glass under impact and blast loading

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    Material-Point Analysis of Large-Strain Problems:modelling of landslides

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    Coupling SPH and thermochemical models of planets: Methodology and example of a Mars-sized body

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    Giant impacts have been suggested to explain various characteristics of terrestrial planets and their moons. However, so far in most models only the immediate effects of the collisions have been considered, while the long-term interior evolution of the impacted planets was not studied. Here we present a new approach, combining 3-D shock physics collision calculations with 3-D thermochemical interior evolution models. We apply the combined methods to a demonstration example of a giant impact on a Mars-sized body, using typical collisional parameters from previous studies. While the material parameters (equation of state, rheology model) used in the impact simulations can have some effect on the long-term evolution, we find that the impact angle is the most crucial parameter for the resulting spatial distribution of the newly formed crust. The results indicate that a dichotomous crustal pattern can form after a head-on collision, while this is not the case when considering a more likely grazing collision. Our results underline that end-to-end 3-D calculations of the entire process are required to study in the future the effects of large-scale impacts on the evolution of planetary interiors.Comment: 29 pages, 10 figures, accepted for publication in Icaru
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