Analysis Of Complex Geometries Research Articles

Systematic approach to generate Historical Building Information Modelling (HBIM) in architectural restoration project

Working with heritage is complex and projects often include scientific, structural, and documentary studies. Every step requires a systematic approach in which the contribution of the diverse experts that participate in the conservation of heritage assets is analysed following the logical sequence of the project execution phase. However, there are still no scientific contributions that record the complete process. A logical sequence, called a ‘systematic approach’ in this paper, should start with data acquisition using remote sensing techniques, the insertion of point cloud data in a Building Information Modelling (BIM) environment, ontologies applied to HBIM (Historic BIM), data classification, and evolution towards the Digital Twin (DT) concept. This paper also analyses the modelling workflow of a case study, the construction of a column base of the Santiago church in Jerez de la Frontera (Spain). This component has been automatically modelled from a mesh in an Autodesk Revit family and through an adaptive mesh process in ArchiCAD. Furthermore, one of the objectives was the data organisation by following and extending a standard data structure of the column components. This paper presents a novel holistic approach from data capture, analysis of complex geometry, construction of the semantically enriched parametric model, and exchange of it among all involved professionals in open source IFC formats. This systematic approach therefore makes it possible to obtain a validated DT for the life-cycle management of architectural elements.

Two-Dimensional Shape Analysis of Complex Geometry Based on Photogrammetric Models of Iconostases

Three-dimensional digitization technologies have been proved as reliable methods for detailed and accurate spatial data collection from existing cultural heritage. In addition, the point segmentation techniques are particularly relevant for contour detection and classification of the unstructured point cloud. This paper describes an approach to obtain 2D CAD-like visualizations of complex geometry from photogrammetric models so that the detected contours of particular object elements can be used for 2D shape analysis. The work process uses the point clouds derived from photogrammetric models to create the plane visualization of the object’s geometry by segmenting points based on the verticality geometric feature. The research presented is on the case studies of iconostases as the specific art and architectural elements of the Christian Orthodox church that can be appreciated only in situ. To determine relations between the characteristics of the particular shapes and the iconostases’ style origins, the mathematical method of shape analysis was applied. This study aims to numerically describe the stylistic characteristics of the shapes of the main parts of the iconostasis concerning the artistic period to which it belongs to. The concept was based on the consideration of global shape descriptors and associated shape measurements which were used to analyze and classify the stylistic characteristics of the iconostases. The methodology was applied to the representative examples of three iconostases from the Baroque and Classicism art movements. The results illustrated that the proposed methods and techniques, with certain improvements, could be helpful for CAD visualization and shape analysis of complex geometry.

A multiregion operator-splitting CFD approach for coupling microkinetic modeling with internal porous transport in heterogeneous catalytic reactors

We propose a multiregion approach to allow for the computational fluid dynamic simulation of heterogeneous fixed bed reactors with a microkinetic description of the surface reactivity and the concomitant account for intraphase transport. A partitioned approach has been considered for the coupling between the different regions. The computational domain is split in different regions, which are characterized by different phenomena. The governing equations in the different regions of the domain are solved separately, followed by the achievement of the convergence at the boundaries through an iterative procedure. Overall, the resulting numerical framework allows for the dynamic solution of reacting flows over solid porous catalysts of arbitrary complex geometries with surface reactivity described by detailed microkinetic mechanisms. The capabilities of the numerical framework are tested through the analysis of complex geometries and large heterogeneous microkinetic models and the simulation of experimental data of H2 combustion on Rh in conditions where internal mass transfer limitations are controlling.

Application of the Upper Bound Theorem to Indentation Processes with Tilted Punch by Means of Modular Model

Nowadays, due to the new deformation processes that are being developed like the Incremental Forming Process (IFP) or the Localized-Incremental Forging Process (LIFP), indentation processes are regaining importance again. In this paper, in order to cover the largest possible number of cases in the study of indentation a tilted punch is considered. Thus, using combinations of flat and tilted punches makes possible the analysis of complex geometries. Present study shows the analysis of the indentation process by the Upper Bound Theorem (UBT) when it is carried out with a tilted punch. A modular model is developed. This modular model is compound by three modules, each with two Triangular Rigid Zones (TRZ), adapting better to the configuration of the punch this way.

Two-dimensional control volume modeling of the resin infiltration of a porous medium with a heterogeneous permeability tensor

Resin Transfer Molding (RTM) is a polymer composite processing technique widely used in the aeronautics and automotive sectors. This paper describes the numerical simulation of the RTM process where Darcy's law was used for the mathematical formulation of the problem. A control volume finite element method was used for the determination of pressure gradients inside the mold, and a geometric reconstruction algorithm is used for the resin flow-front determination. Permeability of the medium was considered either a constant or a two dimensional tensor. The application was validated by direct comparison with literature data and good qualitative and quantitative agreement was obtained. The finite volume method was built to be used with a two-dimensional unstructured grid, hence allowing the analysis of complex geometries. The results showed that the proposed methodology is fully capable of predicting resin flow advancement in a multi-layer (with distinct physical properties) reinforced media.

Study on Large Scale Analysis for Infra-Structure

During the last two decades, the interests of large scale seamless analysis have been increased with respect to lifetime extension and management of infra-structure. And then, a seamless analysis of complex geometry is one of greatly interesting topic. However, there are still gaps between the industrial applications and fundamental academic studies owing to time consuming the modeling and analyzing process. To resolve these problems, the integrity evaluation procedure from knowledge-based information system (KIS) to ADVENTRUE has been proposed for the application of auto mesh generation and large scale analysis. The virtual plant which is used for the master of KIS, provides the 3D information of entities for mesh generation. And then, the ADVENTURE makes a domain decomposed mesh and analyzes it using hierarchical domain decomposition method. Considering the good applicability in both efficiency and exactness point of views, it is anticipated that the proposed study on large scale analysis can be used as a promising integrity evaluation method of infra-structures.

Application of Grid-Based Approach for Auto Mesh Generation of Vacuum Chamber

A seamless analysis of complex geometry is one of greatly interesting topic. However, there are still gaps between the industrial applications and fundamental academic studies owing to time consuming modeling process. To resolve this problem, an auto mesh generation program based on grid-based approach has been developed for IT-product in the present study. At first, base mesh and skin mesh are generated using the information of entities which extracted from IGES file. Secondly the provisional core mesh with rugged boundary geometry is constructed by superimposing the skin mesh as well as the base mesh generated from the CAD model. Finally, the positions of boundary nodes are adjusted to make a qualified mesh by adapting node modification and smoothing techniques. Also, for the sake of verification of mesh quality, the hexahedral auto mesh constructed by the program is compared with the corresponding tetrahedral free mesh and hexahedral mapped mesh through static finite element analyses. Thereby, it is anticipated that the grid-based approach can be used as a promising pre-processor for integrity evaluation of various IT-products.

Speckle classification for sensorless freehand 3-D ultrasound

Despite being a valuable tool for volume measurement and the analysis of complex geometry, the need for an external position sensor is holding up the clinical exploitation of freehand 3-D ultrasound. Some sensorless systems have been developed, using speckle decorrelation for out-of-plane distance estimation, but their accuracy is still not as good as that of sensor-based systems. Here, we examine the widely held belief that accuracy can be improved by limiting the distance measurements to patches of ultrasound data containing fully developed speckle. Without speckle detection, we observe that scan separation is systematically underestimated by 33.1% in biological tissue. We describe a number of speckle detectors and show that they reduce the underestimate to about 25%. We conclude that speckle classification can improve the quality of distance estimation, but not sufficiently to achieve accurate, metric reconstruction of the insonified volume. (E-mail: ph305@eng.cam.ac.uk)

Multidimensional Deterministic Nuclear Data Sensitivity and Uncertainty Code System: Method and Application

In the nuclear industry, an increased demand exists to provide modeling results with credible confidence bounds not only for simple but also for refined modeling. With the objective to facilitate and promote such analysis, a user-friendly and complete computer code package was developed comprising the multidimensional cross-section sensitivity and uncertainty code package SUSD3D, the secondary angular distribution (SAD) covariance data-processing module ERRORR34, and the cross-section covariance matrix library ZZ-VITAMIN-J/COVA.The discrete ordinates sensitivity formulation of the first-order perturbation theory is implemented in the SUSD3D code. Much effort was devoted to mitigate some drawbacks of the discrete ordinates-based sensitivity analysis, in particular to allow the analysis of complex geometries and to reduce memory requirements. The SUSD3D code is linked via interface files to a wide range of state-of-the-art transport codes suitable for complex radiation transport and facility design studies (like ANISN, DOT-3.5, DANTSYS, DORT, and TORT) and supports the new cross-section and covariance data formats. The SAD and secondary energy distribution effects can be taken into account. The complete SAD covariance matrices, as available in the European Fusion File evaluations (EFF-2 and -3) can be treated. The computer codes are written in FORTRAN-77 and run under DOS (PC), UNIX (workstations), VMS (VAX), and other compatible operating systems.The code system is extensively used to study fission- and fusion-related problems. The validation and several practical applications of the package are presented, including the reactor pressure vessel surveillance uncertainty studies, and ASPIS-iron, VENUS-3, and FNG benchmark experiment analyses.

Coupling finite element and boundary element methods for the analysis of the acoustic scattering by elastic structures

Considerable interest has been expressed recently in the scattering of a plane acoustic wave by an elastic structure. In this paper, a method that couples the finite element method and a boundary element method is proposed. A finite element code (ATILA) is used to model the elastic structure and a boundary element code (EQI) to describe the propagating waves in the infinite fluid medium surrounding the body. The analysis is performed in three steps for each frequency: (i) the effect of the fluid is characterized by a nodal impedance matrix using BEM, (ii) the analysis of the structure using FEM including fluid effects via the impedance matrix provides the displacement field, (iii) from these displacements, the near-field and far-field pressures are obtained using BEM. The method is successfully applied to the scattering by spherical shells of various thicknesses for ka varying from 0 to 15 (k is the acoustic wave number in the fluid and a is the external radius of the sphere). The advantages of the method (analysis of complex geometries with various materials, direct knowledge of the displacement field, exact description of Sommerfeld’s radiation condition) and its drawbacks (irregular frequencies associated with BEM, limitation to medium values of ka) are discussed. [Work supported by D.R.E.T. Paris.]

Thermal Analysis of Surface Mounted Leadless Chip Carriers

A thermal analysis has been made of 40 pin leadless chip carriers (LCC) surface mounted on an alumina substrate. Finite element (FE) codes have been used to numerically simulate the problem. We show both theoretically and experimentally that the junction to case temperature is not a convenient parameter for thermal characterization of the heat transfer processes in the complex geometry under consideration. The geometrical complexity of the problem together with the uncertainty of the thermophysical properties and heat transfer coefficients make accurate thermal characterization difficult for parametric study and design analysis. A method, based on homogenization or simplification of a complex region by introducing an effective homogeneous material, is proposed for thermal analysis of complex geometries and its range of applicability is presented. Using this method, different models of heat transfer can be lumped together and various available computer codes can be utilized for rapid thermal design analysis of microelectronic devices.