The discrete multi-physics method applied to biomechanics

In this thesis, a fully Lagrangian approach called the Discrete Multi-Physics is adopted and applied to biomechanics. The Discrete Multi-Physics combines the Smoothed Particle Hydrodynamics, the Mass and Spring Model and the Discrete Element Method in a common particle-based framework. In the Discrete Multi-Physics, high deformations and contact of solid structures (e.g. valve’s leaflets during closing phase or colloid contact) can be easily modelled. In biological valve simulations, for instance, we were able to account for repeated opening-closing cycles and to introduce an agglomeration algorithm to model clotting. Besides cardiovascular and venous flows, we also applied the Discrete Multi-Physics to respiratory tracts for modelling (i) cilia motion and drug diffusion in the periciliary layer (ciliated epithelium) and (ii) the release of active ingredients in powder inhalers for drug delivery in the lungs

Development of a combined solver to model transport and chemical reactions in catalytic wall-flow filters

none5siIn this work, we develop a non-isothermal model for diesel particulate filters including exothermic and competing chemical reactions. We begin with an isothermal, single-reaction model and we gradually increase its complexity. By comparing various models, we aim at establishing the minimum degree of complexity required to effectively model the system under investigation. Based on the numerical simulations, we conclude that isothermal models are adequate only if the temperature of the catalyst is, at all times, completely below or completely above a critical temperature. However, if the goal is to predict the critical temperature, only non-isothermal models should be used. The results with competing reactions, on the other hand, show that the presence of competing reactions does not affect significantly the overall conversion in the filter.noneAllouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Alexiadis A.Allouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Alexiadis A

How to modify LAMMPS: from the prospective of a particle method researcher

LAMMPS is a powerful simulator originally developed for molecular dynamics that, today, also accounts for other particle-based algorithms such as DEM, SPH, or Peridynamics. The versatility of this software is further enhanced by the fact that it is open-source and modifiable by users. This property suits particularly well Discrete Multiphysics and hybrid models that combine multiple particle methods in the same simulation. Modifying LAMMPS can be challenging for researchers with little coding experience. The available material explaining how to modify LAMMPS is either too basic or too advanced for the average researcher. In this work, we provide several examples, with increasing level of complexity, suitable for researchers and practitioners in physics and engineering, who are familiar with coding without been experts. For each feature, step by step instructions for implementing them in LAMMPS are shown to allow researchers to easily follow the procedure and compile a new version of the code. The aim is to fill a gap in the literature with particular reference to the scientific community that uses particle methods for (discrete) multiphysics

Joining of Oxide Dispersion-Strengthened Steel Using Spark Plasma Sintering

Difficulties with joining oxide dispersion-strengthened (ODS) steels using classical welding processes have led to the development of alternative joining techniques such as spark plasma sintering (SPS). SPS, which is classically employed for performing sintering, may also be used to join relatively large components due to the simultaneous application of electrical pulsed current and uniaxial charge. SPS technology was tested by joining two ODS steel disks. The preliminary tests showed that it is necessary to control surface roughness before joining. Furthermore, the use of ground and lapped surfaces seemed to improve the quality of the interface. Tensile tests on two ODS cylinders joined using SPS were performed at 750 °C without any additives. Failure occurred away from the interface with a total elongation close to 50% and an ultimate stress of 110 MPa

Corrigendum to "Development of a combined solver to model transport and chemical reactions in catalytic wall-flow filters" [Chem. Eng. Res. Des. 117 (2016) 681-687]

none7siThe authors regret that two of the authors, Li Liu and Sam K. Wilkinson, were omitted in error during the publication of this article. Hence the full list of authors is now shown in this corrigendum. The authors would like to apologise for any inconvenience caused.noneAllouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Liu L.; Wilkinson S.K.; Alexiadis A.Allouche M.H.; Enjalbert R.; Alberini F.; Ariane M.; Liu L.; Wilkinson S.K.; Alexiadis A

Inelastic light scattering by long narrow gold nanocrystals: when size, shape, crystallinity and assembly matter

International audienceWe report the synthesis of long narrow gold nanocrystals and the study of their vibrational dynamics using inelastic light scattering measurements. Rich experimental spectra are obtained for monodomain gold nanorods and pentagonal twinned bipyramids. Their assignment involves diameter-dependent non-totally symmetric vibrations which are modeled in the framework of continuum elasticity by taking into account simultaneously the size, shape and crystallinity of the nanocrystals. Light scattering by vibrations with angular momenta larger than 2 is reported. It is shown to increase with the ratio of the nanocrystals diameter to the interparticle separation. It originates from the plasmonic coupling due to the self-assembly of the nanocrystals after deposition