Tree-based Control Space Structures for Discrete Metric Sources in 3D Meshing

This article compares the different variations of the octree and kd-tree structures used to create a control space based on a set of discrete metric point-sources. The control space thus created supervises the generation of the mesh providing efficient access to the required information on the desired shape and size of the mesh elements at each point of the discretized domain. Structures are compared in terms of computational and memory complexity as well as regarding the accuracy of the approximation of the set of discrete metric sources in the created control space structure.

As-Built 3D Heritage City Modelling to Support Numerical Structural Analysis: Application to the Assessment of an Archaeological Remain

Terrestrial laser scanning is a widely used technology to digitise archaeological, architectural and cultural heritage. This allows for modelling the assets’ real condition in comparison with traditional data acquisition methods. This paper, based on the case study of the basilica in the Baelo Claudia archaeological ensemble (Tarifa, Spain), justifies the need of accurate heritage modelling against excessively simplified approaches in order to support structural safety analysis. To do this, after validating the 3D meshing process from point cloud data, the semi-automatic digital reconstitution of the basilica columns is performed. Next, a geometric analysis is conducted to calculate the structural alterations of the columns. In order to determine the structural performance, focusing both on the accuracy and suitability of the geometric models, static and modal analyses are carried out by means of the finite element method (FEM) on three different models for the most unfavourable column in terms of structural damage: (1) as-built (2) simplified and (3) ideal model without deformations. Finally, the outcomes show that the as-built modelling enhances the conservation status analysis of the 3D heritage city (in terms of realistic compliance factor values), although further automation still needs to be implemented in the modelling process.

EVALUATION OF GMSH MESHING ALGORITHMS IN PREPARATION OF HIGH-RESOLUTION WIND SPEED SIMULATIONS IN URBAN AREAS

This paper aims to evaluate the applicability of automatically generated meshes produced within the gmsh meshing framework in preparation for high resolution wind speed and atmospheric pressure simulations for detailed urban environments. The process of creating a skeleton geometry for the meshing process based on level of detail (LOD) 2 CityGML data is described. Gmsh itself offers several approaches for the 2D and 3D meshing process respectively. The different algorithms are shortly introduced and preliminary rated in regard to the mesh quality that is to be expected, as they differ inversely in terms of robustness and resulting mesh element quality. A test area was chosen to simulate the turbulent flow of wind around an urban environment to evaluate the different mesh incarnations by means of a relative comparison of the residuals resulting from the finite-element computational fluid dynamics (CFD) calculations. The applied mesh cases are assessed regarding their convergence evolution as well as final residual values, showing that gmsh 2D and 3D algorithm combinations utilizing the Frontal meshing approach are the preferable choice for the kind of underlying geometry as used in the on hand experiments.

Abstract 16108: Adverse Left Ventricular Remodelling Patterns Predict Response to Cardiac Resynchronization Therapy

Introduction: The anatomy of the left ventricle (LV) remodels in heart failure. In this work we test the hypothesis that pre-implant LV shape can predict response to cardiac resynchronization therapy (CRT). Methods: The anatomy of the LV of 50 subjects selected for CRT was acquired and manually segmented from magnetic resonance imaging acquired using a steady-state free-precision 3D sequence. A computational atlas was built from 3D meshes that were fitted to the resulting segmentations, and was used to obtain atlas-based shape metrics from the cohort. Segmentation and 3D meshing was repeated in 19 cases to test the reproducibility of the new metrics. Results: The five most significant shape metrics were found to be reproducible. Response to CRT, defined as a reduction of a 10% in the end diastolic volume, was predicted by a linear combination of 2 atlas modes (AUC of 0.693, best operating point with sensitivity of 84% and specificity of 56%, as evaluated by a leave-1-out cross-validation test). The figure illustrates the overlay of the extreme geometry of responder (velvet) and non-responder (orange) shapes computed from the statistical shape model (the small red sphere is located at the septal wall): the adverse LV remodelling shows a shorter septal wall and angled basal plane. Conclusions: Pre-implant LV shape, described through novel atlas-based metrics, is a potential new criterion for CRT patient selection.

Modelling the effect of gaps and overlaps in automated fibre placement (AFP)-manufactured laminates

In automated fibre placement (AFP) process, gaps and overlaps parallel to the fibre direction can be introduced between the adjoining tapes. These gaps and overlaps can cause a reduction in strength compared with pristine conditions. Finite element modelling is an effective way to understand how the size and distribution of such gaps and overlaps influences the strength and failure development. Many modelling work showed that out-of-plane waviness and ply thickness variations caused by gaps and overlaps play an important role in inducing the strength knock-down; however, there has been a lack of effective way to explicitly model the ply waviness, which constrained the relevant research. In this work, 3D meshing tools were developed to automatically generate ply-by-ply models with gaps and overlaps. Intra-ply and inter-ply cohesive elements are also automatically inserted in the model to capture the influence of splitting and delamination. Out-of-plane waviness and ply thickness variations caused by gaps and overlaps are automatically modelled. Models with various sizes and distribution of gaps and overlaps were built to predict the reduction of strength as a function of the magnitude and type of the defects. Results of gap and overlap models will be used to guide future experimental characterization of simulated AFP process defects, manufactured by hand layup from pre-preg tape.