4,169 research outputs found
Micro computed tomography based finite element models of calcium phosphate scaffolds for bone tissue engineering
Bone is a living tissue that is able to regenerate by itself. However, when severe bone defects occur, the natural regeneration may be impaired. In these cases, bone graft substitutes can be used to induce the natural healing process. As a scaffold for tissue engineering, these bone graft substitutes have to meet specific requirements. Among others, the material must be biocompatible, biodegradable and have a porous structure to allow vascularization, cell migration and formation of new bone. Additionally, the mechanical properties of the scaffold have to resemble the ones of native tissue. The goal of this project is to create a computational model of the calcium phosphate scaffolds that are produced by rapid-prototyping by the Biomaterials, Biomechanics, and Tissue Engineering group at the Technical University of Catalonia. These models are based on finite element analysis and micro computed tomography images in order to consider the actual architecture of the scaffolds. The generated FE-models allow the computation of both local strains, which act as mechanical stimuli on attached cells, as well as the behaviour of the entire scaffold. When considering this information, the scaffold can be optimized for tissue differentiation by tuning both the scaffold architecture and the scaffold material bulk properties.Incomin
A FIC-based stabilized finite element formulation for turbulent flows
We present a new stabilized finite element (FEM) formulation for incompressible flows based on the Finite
Increment Calculus (FIC) framework. In comparison to existing FIC approaches for fluids, this formulation
involves a new term in the momentum equation, which introduces non-isotropic dissipation in the direction of
velocity gradients. We also follow a new approach to the derivation of the stabilized mass equation, inspired by
recent developments for quasi-incompressible flows. The presented FIC-FEM formulation is used to simulate
turbulent flows, using the dissipation introduced by the method to account for turbulent dissipation in the style
of implicit large eddy simulation.Peer ReviewedPostprint (author's final draft
Low-order continuous finite element spaces on hybrid non-conforming hexahedral-tetrahedral meshes
This article deals with solving partial differential equations with the
finite element method on hybrid non-conforming hexahedral-tetrahedral meshes.
By non-conforming, we mean that a quadrangular face of a hexahedron can be
connected to two triangular faces of tetrahedra. We introduce a set of
low-order continuous (C0) finite element spaces defined on these meshes. They
are built from standard tri-linear and quadratic Lagrange finite elements with
an extra set of constraints at non-conforming hexahedra-tetrahedra junctions to
recover continuity. We consider both the continuity of the geometry and the
continuity of the function basis as follows: the continuity of the geometry is
achieved by using quadratic mappings for tetrahedra connected to tri-affine
hexahedra and the continuity of interpolating functions is enforced in a
similar manner by using quadratic Lagrange basis on tetrahedra with constraints
at non-conforming junctions to match tri-linear hexahedra. The so-defined
function spaces are validated numerically on simple Poisson and linear
elasticity problems for which an analytical solution is known. We observe that
using a hybrid mesh with the proposed function spaces results in an accuracy
significantly better than when using linear tetrahedra and slightly worse than
when solely using tri-linear hexahedra. As a consequence, the proposed function
spaces may be a promising alternative for complex geometries that are out of
reach of existing full hexahedral meshing methods
Turbulent jet simulation using high-order DG methods for aeroacoustics analysis
In this work, a high-order discontinuous Galerkin (DG) method is used to
perform a large-eddy simulation (LES) of a subsonic isothermal jet at high
Reynolds number Re D = 10^6 on a fully un-structured mesh. Its radiated
acoustic field is computed using the Ffowcs Williams and Hawkings formulation.
In order to assess the accuracy of the DG method, the simulation results are
compared to experimental measurements and a reference simulation based on a
finite volume method. The comparisons are made on the flow quantities (mean,
rms and spectra) and pressure far field (rms and spectra)
GPU-accelerated discontinuous Galerkin methods on hybrid meshes
We present a time-explicit discontinuous Galerkin (DG) solver for the
time-domain acoustic wave equation on hybrid meshes containing vertex-mapped
hexahedral, wedge, pyramidal and tetrahedral elements. Discretely energy-stable
formulations are presented for both Gauss-Legendre and Gauss-Legendre-Lobatto
(Spectral Element) nodal bases for the hexahedron. Stable timestep restrictions
for hybrid meshes are derived by bounding the spectral radius of the DG
operator using order-dependent constants in trace and Markov inequalities.
Computational efficiency is achieved under a combination of element-specific
kernels (including new quadrature-free operators for the pyramid), multi-rate
timestepping, and acceleration using Graphics Processing Units.Comment: Submitted to CMAM
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