34,422 research outputs found
Nonintrusive coupling of 3D and 2D laminated composite models based on finite element 3D recovery
In order to simulate the mechanical behavior of large structures assembled
from thin composite panels, we propose a coupling technique which substitutes
local 3D models for the global plate model in the critical zones where plate
modeling is inadequate. The transition from 3D to 2D is based on stress and
displacement distributions associated with Saint-Venant problems which are
precalculated automatically for a simple 3D cell. The hybrid plate/3D model is
obtained after convergence of a series of iterations between a global plate
model of the structure and localized 3D models of the critical zones. This
technique is nonintrusive because the global calculations can be carried out
using commercial software. Evaluation tests show that convergence is fast and
that the resulting hybrid model is very close to a full 3D model
Hybrid finite difference/finite element immersed boundary method
The immersed boundary method is an approach to fluid-structure interaction that uses a Lagrangian
description of the structural deformations, stresses, and forces along with an Eulerian description of the
momentum, viscosity, and incompressibility of the fluid-structure system. The original immersed boundary
methods described immersed elastic structures using systems of flexible fibers, and even now, most
immersed boundary methods still require Lagrangian meshes that are finer than the Eulerian grid. This
work introduces a coupling scheme for the immersed boundary method to link the Lagrangian and Eulerian
variables that facilitates independent spatial discretizations for the structure and background grid. This
approach employs a finite element discretization of the structure while retaining a finite difference scheme
for the Eulerian variables. We apply this method to benchmark problems involving elastic, rigid, and actively
contracting structures, including an idealized model of the left ventricle of the heart. Our tests include cases
in which, for a fixed Eulerian grid spacing, coarser Lagrangian structural meshes yield discretization errors
that are as much as several orders of magnitude smaller than errors obtained using finer structural meshes.
The Lagrangian-Eulerian coupling approach developed in this work enables the effective use of these coarse
structural meshes with the immersed boundary method. This work also contrasts two different weak forms
of the equations, one of which is demonstrated to be more effective for the coarse structural discretizations
facilitated by our coupling approach
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