Examinando por Autor "Pedrolli, Lorenzo"

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    Comparison of CFD-DEM and MP-PIC in the simulation of metal powder conveying for Laser Metal Deposition
    (OpenCFD Ltd, 2024) Pedrolli, Lorenzo; Achiaga, Beatriz; Martínez de Arenaza, Inger; López García, Alejandro
    Pneumatic conveying of fine powders is essential for many industrial processes, includingLaser Metal Deposition (LMD), a Direct Metal Additive Manufacturing (DMAM) technology that buildssolid objects layer-by-layer using a laser to melt metal powder. To optimize the process, it is necessaryto have a correct understanding of the powder’s behaviour under the process condition.The coupled Computational Fluid Dynamics - Discrete Element Modelling (CFD-DEM) and MultiPhase- Particle In Cell (MP-PIC) are two popular Eulerian-Lagrangian models to simulate particleladen flows. This study compares them to analyse powder behaviour in a small channel of LMD machines.Results from the two methods differ significantly, with CFD-DEM offering a more accuraterepresentation of the physical reality, while MP-PIC is more computationally efficient. The study findsthat the CFD-DEM method produces higher fluctuations in the solids flow rate due to the formationof particle clusters, while MP-PIC displays a smooth and essentially uniform flow. The results suggestthat CFD-DEM should be used for more accurate and detailed studies of solids flow rate in pneumaticconveying systems, while MP-PIC can be used for preliminary studies and design optimization.
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    Estimation of mesoscale surface energy in the kinetic adhesion test
    (Elsevier B.V., 2024-02-15) Pedrolli, Lorenzo; Nadimi, Sadegh; Achiaga, Beatriz; López García, Alejandro
    The Johnson-Kendall-Roberts (JKR) contact model is widely accepted for the elastic adhesive contacts of particles. In this work, we present a novel interpretation of the JKR model that allows for the development of a test procedure with practical hardware called the Kinetic Adhesion Test. The Kinetic Adhesion Test is based on the balance between kinetic and adhesive energy and allows for the determination of the mesoscale adhesive energy, Γ. The work not only presents the test procedure but also provides a derivation of the formula to determine Γ. This test procedure has been validated by experimental results compared with direct measurement of the contact radius. Overall, the presented work provides a practical approach for determining adhesive energy, which is an essential factor in accurately simulating powder behaviour using DEM. This work contributes to the advancement of the accuracy of DEM simulations and, therefore, to the improvement of research in multiple fields, including materials science, engineering, and pharmaceuticals.
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    Kinetic adhesion test to determine particle surface energy
    (Elsevier Ltd, 2023-06-01) Pedrolli, Lorenzo; Nadimi, Sadegh; Maramizonouz, Sadaf; Achiaga, Beatriz; López García, Alejandro
    A new hardware is described to quantify the particle surface energy by assuming that the Johnson Kendall and Roberts theory of elastic-adhesive contacts is applicable. The setup is used in the active section of the measurement, where newly designed elements provide the sharp impact needed to detach the particles under the action of their own kinetic energy. It employs a selection of sensors to provide the necessary measurements in a streamlined procedure, which lets the user complete one test in less than one minute. The temporal resolution is 1μs for the contact time measurement and the velocity has a repeatability of 1%. The surface energy is a significant parameter for the characterisation of particulate materials and is widely used in Discrete Element simulations of the bulk behaviour.
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    Optical particle yracking in the pneumatic conveying of metal powders through a thin capillary pipe
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024-10-03) Pedrolli, Lorenzo; Fraccarollo, Luigi; Achiaga, Beatriz; López García, Alejandro
    Directed Energy Deposition (DED) processes necessitate a consistent material flow to the melt pool, typically achieved through pneumatic conveying of metal powder via thin pipes. This study aims to record and analyze the multiphase fluid–solid flow. An experimental setup utilizing a high-speed camera and specialized optics was constructed, and the flow through thin transparent pipes was recorded. The resulting information was analyzed and compared with coupled Computational Fluid Dynamics-Discrete Element Modeling (CFD-DEM) simulations, with special attention to the solids flow fluctuations. The proposed methodology shows a significant improvement in accuracy and reliability over existing approaches, particularly in capturing flow rate fluctuations and particle velocity distributions in small-scale systems. Moreover, it allows for accurately analyzing Particle Size Distribution (PSD) in the same setup. This paper details the experimental design, video analysis using particle tracking, and a novel method for deriving volumetric concentrations and flow rate from flat images. The findings confirm the accuracy of the CFD-DEM simulations and provide insights into the dynamics of pneumatic conveying and individual particle movement, with the potential to improve DED efficiency by reducing variability in material deposition rates.