Now showing 1 - 7 of 7
  • Publication
    A fluid-structure interaction study of biofilm detachment
    (Computational & Mathematical Biomedical Engineering (CMBE), 2009-07-01) ; ; ;
    During the biofilm development process, bacterial cells may detach from the biofilm into the surrounding fluid. The key question in relation to detachment from bacterial biofilm is the mechanical response to hydrodynamic forces. In this study, a Finite Volume Method (FVM) based Fluid-Structure Interaction (FSI) solver in OpenFOAM package has been developed to model the biofilm response to flow [1]. Dynamic interaction was simulated between an incompressible Newtonian fluid and a bacterial biofilm described as a linear viscoelastic solid. Viscoelastic response of the biofilm was represented by the hereditary integral form of constitutive relation [2] while tensile relaxation modulus was expressed by the Generalised Maxwell Model (GMM) in the form of Prony series (a discrete retardation spectrum). GMM was obtained from the rheometry creep experimental data using a three-step method proposed by Dooling et al. [3]. The creep curves were all viscoelastic in nature and approximated by a linear viscoelastic model represented by Generalised Voigt Model (GVM). Elastic shear modulus (G), obtained from the three-step method, ranged from 583Pa to 1368Pa which were similar to the previous rheometry studies. In this two-dimensional model, biofilm was considered as semi-semispherical shape (thickness of 100μm and width of 346μm) attached to the center of the bottom boundary of the square cross-section flow cell. Fluid flow through the flow cell was in laminar regime. Simulation results predicted the potential site for biofilm detachment subjected to increasing fluid flow rate through the flow cell.
  • Publication
    Mechanical properties of a mature biofilm from a wastewater system: from microscale to macroscale level
    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.
      5Scopus© Citations 21
  • Publication
    Finite-volume stress analysis in multi-material linear elastic body
    (Wiley Blackwell (John Wiley & Sons), 2012-07-05) ; ;
    Correct calculation of stresses at the interface of bonded or otherwise joined materials plays a significant role in many applications. It is therefore important that traction at the material interface is calculated as accurately as possible. This paper describes procedures that can be employed to achieve this goal by using centre-based finite-volume method. Total traction at the interface is calculated by decomposing it into normal and tangential components, both being calculated at each side of the interface, and applying the continuity assumption. The way in which the traction approximation is achieved depends on calculation of tangential gradient of displacement at the interface. To this end, three different methods are proposed and validated against problems with known solutions. It was shown that all methods can be successfully used to simulate problems with multi-material domains, with the procedure based on finite area method being most accurate.
      1165Scopus© Citations 41
  • Publication
    A Block-Coupled Finite Volume Methodology for Linear Elasticity and Unstructured Meshes
    The current article presents a new implicit cell-centred Finite Volume solution methodology for linear elasticity and unstructured meshes. Details are given of the implicit discretisation, including use of a Finite Area method for face tangential gradients and implicit non-orthogonal correction. A number of 2-D and 3-D linear-elastic benchmark test cases are examined using hexahedral, tetrahedral and general polyhedral meshes; solution accuracy and efficiency are compared with that of a segregated procedure and a commercial Finite Element software, where the new method is shown to be faster in all cases.
      698Scopus© Citations 54
  • Publication
    Hierarchical RVE-based multiscale modelling of non-linear heterogeneous materials using the finite volume method
    This paper describes the development of a hierarchical multiscale procedure within the finite volume OpenFOAM framework for modelling the mechanical response of non-linear heterogeneous solid materials. This is a first development of hierarchical multi-scale model for solid mechanics to use the finite volume discretisation method. In this computational procedure the information is passed between the macro and micro scales using representative volume elements (RVE), allowing for general, non-periodic microstructures to be considered. Each computational point at the macro scale is assigned an RVE with prescribed microstructural features. The overall macro response accounts for the microstructural effects through the coupling of macro and micro scales, i.e., the macro deformation gradient is passed to the RVE and in turn, the homogenised micro stress-strain response is passed back to the macro scale. The incremental total Lagrangian formulation is used to represent the equilibrium state of the solid domain at both scales and its integral equilibrium equation is discretised using the cell-centred finite volume (FV) method in OpenFOAM. The verification of the model is demonstrated using both 2D and 3D simulations of perforated elastic-plastic plates subjected to tensile loading.
  • Publication
    Arbitrary crack propagation in multi-phase materials using the finite volume method
    An arbitrary crack propagation model using cell-centre nite volume based method is presented. Crack growth in an elastic solid, across an interface perpendicular to the initial crack path and into a second elastic solid is analysed. Crack initiation and the subsequent path of propagation are shown to arise naturally out of the selection of appropriate cohesive parameters. It is shown that the allowable crack propagation path is restricted by the underlying mesh. Results are presented for a number of values of interfacial strength and ratios of elastic properties between the two elastic solids. For higher values of interfacial strength, the crack is shown to propagate straight through the interface, while for lower values of interfacial strength, the crack is shown to change direction and propagate along the interface. It is shown that with careful selection of material and interface parameters it is possible to arrest a propagating crack at the interface. The method represents a useful step towards the prediction of crack propagation in complex structures.
      613Scopus© Citations 28
  • Publication
    A Lagrangian Cell-Centred Finite Volume Method for Metal Forming Simulation
    The current article presents a Lagrangian cell-centred finite volume solution methodology for simulation of metal forming processes. Details are given of the mathematical model in updated Lagrangian form, where a hyperelastoplastic J2 constitutive relation has been employed. The cell-centred finite volume discretisation is described, where a modified discretised is proposed to alleviate erroneous hydrostatic pressure oscillations; an outline of the memory efficient segregated solution procedure is given. The accuracy and order of accuracy of the method is examined on a number of 2-D and 3-D elastoplastic benchmark test cases, where good agreement with available analytical and finite element solutions is achieved.
      716Scopus© Citations 16