Multiscale Modeling Group

Welcome to the Multiscale Modeling Group. We aim to design high-throughput process models for advanced manufacturing of metal-based alloys and nanocomposites. Our models cover a wide range of length- and time-scales while being developed and tested with commercial and open-source software on various computing infrastructures from regular workstations to supercomputers. Through close internal and external collaborations, we also carry out our benchmark and validation experiments as well as advanced statistical analysis and machine learning. Currently, we are pursuing two main research directions (RDs) as defined below.


RD1: Developing multi-physics models for metal 3D printing

 

Our approach

We adopt the Eulerian-Lagrangian framework to numerically describe the multiphysics nature of metal 3D printing. We use

  • Computational Fluid Dynamics (CFD) based on Finite Volume Method (FVM) to model heat and mass transport in each phase as well as solid-liquid phase transitions in the substrate

  • Volume-of-Fluid (VOF) method to model solid-gas and liquid-gas interfaces, involving multiphase flow

  • Discrete Element Method (DEM) to model powder particles and laser photons and their interactions

We develop and apply customized subroutines for the CFD-DEM-VOF coupling to describe particle-fluid and particle-interface interactions, also including laser-matter interactions.

Our tools

  • OpenFOAM - open-source FVM-based software designed for CFD simulations 

  • Aspherix - commercial DEM software designed for modeling granular media

  • CFDEM coupling - commercial software designed for modeling particle-fluid interactions with partially open code allowing for customized subroutines for CFD-DEM coupling using OpenFOAM and Aspherix

  • ParaView - open-source software used for post-processing and visualization of simulation results from software listed above

Representative publications

  1. A simple scaling model for balling defect formation during laser powder bed fusion, Additive Manufacturing (2023)

  2. Investigation of the transient coupling between the dynamic laser beam absorptance and the melt pool - vapor depression morphology in laser powder bed fusion process, International Journal of Heat and Mass Transfer (2023)

  3. An integrated Eulerian-Lagrangian-Eulerian investigation of coaxial gas-powder flow and intensified particle-melt interaction in directed energy deposition process, International Journal of Thermal Sciences (2021)

  4. Role of impinging powder particles on melt pool hydrodynamics, thermal behaviour and microstructure in laser-assisted DED process: A particle-scale DEM – CFD – CA approach, International Journal of Heat and Mass Transfer (2020)


RD2: Employing atomistic simulations and ab initio calculations for nanoscale materials design

Our approach

We adopt major open-source community codes for atomistic simulations and quantum calculations to access various processes and properties of materials at the nanoscale. We rely on well-established theories and phenomenological modeling to analyze and interpret our modeling results as well as guide the development of new theories and mesoscale modeling tools.

Our tools

  • LAMMPS - a high-performance atomistic modeling code enabling large-scale atomistic simulations with millions or even billions of atoms
  • Quantum ESPRESSO -an integrated suite of open-source codes for electronic-structure calculations and materials modeling at the nanoscale based on density-functional theory, plane waves, and pseudopotentials
  • CP2K - a quantum chemistry and solid state physics software package providing a general framework for different modeling methods such as DFT using the mixed Gaussian and plane waves approaches
  • OVITO - a visualization and analysis software for output data generated in molecular dynamics, atomistic Monte-Carlo and other particle-based simulations (partially commercial, premium licenses available in the group)

Representative publications:

  1. Atomistic Assessment of Melting Point Depression and Enhanced Interfacial Diffusion of Cu in Confinement with AlN, ACS Applied Materials & Interfaces (2022)

  2. Prediction of a wide variety of linear complexions in face centered cubic alloys, Acta Materialia (2020)

  3. Grain boundary complexions and the strength of nanocrystalline metals: Dislocation emission and propagation, Acta Materialia (2018)

  4. Modeling self-sustaining waves of exothermic dissolution in nanometric Ni-Al multilayers, Acta Materialia (2016)


TEAM PHOTOS

The first generation (2020-2022)  - August 2022 - Thun

Team leader

Dr. Vladyslav Turlo

Expert in large-scale atomistic simulations

Scientists

Dr. Akash Aggarwal

Expert in mesoscale multi-physics modeling

Project: Multiphysics modeling of laser metal 3D printing

Ph.D. students

Simon Gramatte

Project: Atomistic modeling of systems with complex chemical bonding

 


Finished projects and alumni

Postdoctoral projects

PhD-related projects

Master theses

Internships

  • Stefan Scharen (2022): Atomistic simulations of heterogeneous nucleation
  • Yann Muller (2022): Ab initio modeling of Cu/AlN nano-multilayers
  • Stephane Nilsson (2021): Bayesian inference for multiphysics models of laser melting
  • Daniele Hamm (2021): Bayesian inference for heat transfer models of laser melting
  • Jose Simon Greminger (2021): Atomistic modeling of heterogeneous nucleation
  • Jose Simon Greminger (2020): Atomistic modeling of alumina nanoparticles