OpenFOAM Finite Volume Solver for Fluid-Solid Interaction

This paper describes a self-contained parallel fluid-structure interaction solver based on a finite volume discretisation, where a strongly coupled partitioned solution procedure is employed. The incompressible fluid flow is described by the Navier-Stokes equations in the arbitrary Lagrangian-Eulerian form, and the solid deformation is described by the Saint Venant-Kirchhoff hyperelastic model in the total Lagrangian form. Both the fluid and the solid are discretised in space using the second-order accurate cell-centred finite volume method, and temporal discretisation is performed using the second-order accurate implicit scheme. The method, implemented in open-source software OpenFOAM, is parallelised using the domain decomposition approach and the exchange of information at the fluid-solid interface is handled using global face zones. The performance of the solver is evaluated in standard two- and threedimensional cases and excellent agreement with the available numerical results is obtained

Mechanical properties of a mature biofilm from a wastewater system: From microscale to macroscale level

<div><p>A fundamental understanding of biofilm mechanical stability is critical in order to describe detachment and develop biofouling control strategies. It is thus important to characterise the elastic deformation and flow behaviour of the biofilm under different modes of applied force. In this study, the mechanical properties of a mature wastewater biofilm were investigated with methods including macroscale compression and microscale indentation using atomic force microscopy (AFM). The mature biofilm was found to be mechanically isotropic at the macroscale level as its mechanical properties did not depend on the scales and modes of loading. However, the biofilm showed a tendency for mechanical inhomogeneity at the microscale level as indentation progressed deeper into the matrix. Moreover, it was observed that the adhesion force had a significant influence on the elastic properties of the biofilm at the surface, subjected to microscale tensile loading. These results are expected to inform a damage-based model for biofilm detachment.</p></div

A numerical study of processing parameters and their effect on the melt-track profile in Laser Powder Bed Fusion processes

Mathematical models provide valuable insight into the Laser Beam Powder Bed Fusion (PBF-LB) process. Numerical modelling of the PBF-LB process and the influence of the process parameters on the melt pool topology are presented in this study. A one-way coupled model using Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) is adopted to model the particle distribution in the powder bed and the melt pool formation and dynamics due to laser irradiation during the PBF process. The DEM method is used to model the interaction between particles in the powder bed, and CFD is used to simulate the melt pool formation, flow and solidification. The Volume of Fluid (VoF) approach was used to model the three phases. The effects of surface tension, Marangoni convection and recoil pressure at the metal/gas interface were included in this model. The predicted melt pool dimensions for various process parameters are validated against the experimental data. The different pore-forming mechanisms in multi-track, multi-layer cases and the effect of actual layer thickness are investigated. The proposed modelling approach is shown to capture the dominant physical mechanisms of the PBF-LB processes, potentially being used as a tool to understand process-structure–property relationships and aid in process optimisation.</p

Fatigue delamination behaviour of carbon fibre/epoxy composites interleaved with thermoplastic veils

Interleaving thermoplastic veils has proved to enhance the interlaminar fracture toughness of carbon fibre/epoxy composites under static loading conditions. However, the fatigue delamination behaviour has yet to be investigated. Herein, meltable Polyamide-12 (PA) veils and non-meltable Polyphenylene-sulphide (PPS) veils were used for interlay toughening of unidirectional (UD) and non-crimp fabric (NCF) laminates that were manufactured using a prepreg process and resin transfer moulding process, respectively. The results of Mode-I fatigue delamination tests demonstrated a significant improvement in the fatigue life of the laminates due to interleaving. Additionally, the fatigue resistance energy has been maximumly increased by 143% and 190% for the UD and NCF laminates, respectively. The microscopy analysis revealed that the toughening mechanisms of thermoplastic veils were affected by the form of the thermoplastic veils in the laminates (melted or non-melted), the fracture mechanisms of the reference laminates and the adhesion/miscibility between the thermoplastic veils and the epoxy.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite