A Modeling Paradigm for Product Specific Design Analysis Integration

It is important to establish an integrated CAD system for mechanical engineering. The geometric model is constructed with primitives, such as wire frame, surface and solid on this system. The finite element model is induced from the substructure, which is a component of the geometric model. After the extraction of the substructure from the model, the mesh for the finite element analyses is automatically generated against the substructure. An approach to automatic mesh generation is discussed on this paper, based upon the techniques of interpolation with the blending function, originally developed for geometric modeling. But, the blending function may produce unexpected results when the mesh is generated, due to the nature of the algorithm. In order to conclude with expected results for automatic mesh generation, and accuracy-fitting method is introduced.

A fuzzy logic knowledge-based approach, FUZZYMESH, for finite element mesh generation and analysis is presented. The proposed approach initiates the adaptive process with a high quality initial mesh that is more refined around the critical points/regions in the problem domain. In order to create high quality initial meshes, the heuristic knowledge, past experience, common sense, and ad hoc methods of finite element specialists are incorporated into the knowledge base of the fuzzy system. Using the linguistic variable concept and approximate reasoning techniques, the fuzzy system makes expert decisions about the initial mesh design by considering the geometric information, as well as the boundary and loading conditions. The decision process includes the determination of priority of critical points/regions and the prediction of mesh sizes for them. According to the mesh size information, a near-optimal initial mesh is created with an automatic mesh generator that is based on the advancing front mesh generation technique. The performance of the proposed approach was measured and evaluated in terms of efficiency and accuracy. The evaluation included comparison between the results of a code based on the proposed fuzzy logic knowledge-based approach, FUZZYMESH, and the conventional approach, which starts the finite element analysis with different meshes, by solving various problems. The global as well as local errors of different solutions were examined and compared. The CPU times for different approaches to achieve a particular accuracy were also measured and compared. The results showed that due to better quality of initial meshes, FUZZYMESH results in lower levels and more accurate error estimates. In turn, the proposed approach is able to solve the problem with a more accurate solution at less cost.

In this paper, we are interested in the forming of composite fabric by deep-drawing. Two approaches (geometrical and mechanical) are proposed for the simulation of the composite fabric forming. The geometrical approach is based on a fishnet model. It is well adapted to preliminary design phase and to give a suitable estimate of the resulting flat patterns. The mechanical approach is based on a meso-structural approach. It allows us to take into account the mechanical properties of composite fabric (fibres and resin) and the various dominant modes of deformation of fabrics during the forming process. During simulation of composite fabric forming, where large displacement and relative rotation of fibres are possible, severe mesh distortions occur after a few incremental steps. Hence an automatic mesh generation with remeshing capabilities is essential to carry out the finite element analysis. Some numerical simulations of forming process are proposed and compared with the experimental results in order to demonstrate the efficiency of the proposed approaches.

Dangers inherited in shells optimized with linear assumptions

A self-adaptive mesh scheme for the Finite Element (FEM) analysis of microwave transmission-lines, is presented. It provides an accurate and efficient FEM program, with automatic mesh generation, well adapted to field distribution and singularities. The method is based on the analysis of the error of the FEM application to a given discretization mesh of the structure under study, that indicates if the grid must be refined and which elements must be subdivided. An efficient procedure for the elements subdivision has been selected comparing results of two different ones.

2D automatic body-fitted structured mesh generation using advancing extraction method

A methodology for the automatic mesh generation of quadrilateral elements is proposed. The methodology is based on the facts that (i) a region can always be subdivided entirely into quadrilaterals if the polygon which forms the boundary of the region has an even number of sides, (ii) a quadrilateral can be formed by two triangles which share a common side. By taking advantage of the techniques developed in an existing automatic triangular mesh generator, quadrilateral meshes can be generated according to the distribution of user specified element size over the domain of interest. In particular, an automatic quadrilateral mesh generator based on the advancing front technique for triangular mesh generation1 is described. Techniques to improve the quality of the generated quadrilateral meshes are introduced. The robustness and versatility of the mesh generator are demonstrated by a variety of examples.

Finite Element Analysis (FEA) and experimental techniques based laboratory courses are used in the mechanical engineering curriculum to equip students with numerical and experimental abilities to solve design problems. Review of mechanical engineering curricula in US universities found no definite structure for the numerical and experimental based laboratory courses to support the core courses. Also, the authors found that due to lack of knowledge about the application of finite element analysis and lack of collaboration of experimental laboratories in the universities and colleges, students are unable to apply theory, numerical tool and experiment, when it comes to complete product design. To be effective product development engineers, students have to know how to use these engineering tools effectively for various mechanical systems to design a product with perfection. This motivated the authors to develop, teach, and evaluate a laboratory course before the senior design project, where students will have hands on experience with product design. The application of theoretical, numerical and experimental techniques, and their interconnectedness, will also be addressed in this new course. The main three learning objectives of this course were: (1) the ability to apply physical and mathematical models to analyze or design the mechanical systems; (2) the ability to use numerical tools (e.g., FEA) and a fundamental understanding of the limitations of such tools; and (3) the ability to correlate the theoretical knowledge with FEA and experimental findings. Some of the issues observed from the previously taught FEA laboratory related course are: (1) students do not understand how to use FEA tools in practical design problems; (2) students are unable to relate the theory with numerical and experimental result; (3) students do not understand the importance of verification of numerical results; and (4) students with knowledge of a particular analysis background have problems setting up the product design requirements dealing with different analysis systems. To overcome these difficulties, the proposed course will select design problems related to heat, fluid, vibration, and fracture and examine the overall design process including preliminary design, material selection, manufacturing, analysis, and testing. Simulating the complexity of “real world” engineering will prepare students for their senior design projects. The main benefits of this course are: (1) application of theoretical, numerical, and experimental techniques to solve a design problem, and (2) hands on experience with design problems.

<div class="section abstract"><div class="htmlview paragraph">Prediction of in-cylinder flows and fuel-air mixing are two fundamental pre-requisites for a successful simulation of direct-injection engines. Over the years, many efforts were carried out in order to improve available turbulence and spray models. However, enhancements in physical modeling can be drastically affected by how the mesh is structured. Grid quality can negatively influence the prediction of organized charge motion structures, turbulence generation and interaction between in-cylinder flows and injected sprays. This is even more relevant for modern direct injection engines, where multiple injections and control of charge motions are employed in a large portion of the operating map. Currently, two different approaches for mesh generation exist: manual and automatic. The first makes generally possible to generate high-quality meshes but, at the same time, it is very time consuming and not completely free from user errors. Automatic mesh generation is very fast, but does not easily allow to align grid with flow and spray in regions of interest, for instance where fuel is injected or where the air flow is confined between pipe walls and thigh gaps (intake and exhaust head ducts and valve gaps). Within this context, the authors have developed a novel approach for automatic mesh generation, where both mesh quality and flow alignment are taken into account. Such methodology has been incorporated into the Lib-ICE code, which is based on the OpenFOAM technology. On the basis of combustion chamber details and/or user specified parameters (piston bowl points, injector direction, squish height, valve lift diagram,…), body fitted, high quality grids are automatically generated to perform full-cycle or compression/combustion simulations. To assess the proposed approach, two direct-injection engines were simulated. The first is Diesel fueled and only compression and combustion phases are simulated, showing the advantages of a spray-oriented grid, compared to a conventional Cartesian one, in terms of prediction of fuel-air mixing and combustion process. The second one is a gasoline, direct-injection engine. In this case full-cycle simulations were performed and computed flow field data were compared with optical experimental ones.</div></div>

The current paradigm for clinical diagnostic for the treatment of vascular disease relies exclusively on diagnostic imaging data to define the present state of the patient, empirical data to evaluate the efficacy of prior treatments for similar patients. These techniques are insufficient to predict the outcome of a given treatment for an individual patient. We here propose a new paradigm of predictive medicine where physician could use computational simulation to construct and evaluate a specific geometrical/anatomical model to predict the outcome for an individual patient. For this purpose it is necessary to develop a complex software system which combines user friendly interface, automatic solid modeling, automatic finite mesh generation, computational fluid dynamics and post-processing visualization. The flow dynamics is defined according to the incompressible Navier-Stokes equations for Newtonian and non-Newtonian fluids. Mass transport of oxygen and macromolecules is modeled by the convection diffusion equation and coupled with flow dynamics. The computer simulations are based upon finite element analysis where the new computer methods for coupling oxygen transport and fluid flow are described. The comparison results shows a good agreement between clinical observation for critical zones of flow separation, flow recirculation, low wall shear stresses which may contribute to the development of atherosclerotic diseases.

As engineering systems are increasingly becoming more complex, the need for information models is growing accordingly. Extensive research is currently underway to develop engineering data management capabilities and to understand the role of information as a systems integrator. In order to develop information models more effectively, a systematic methodology is needed to better manage data and develop information models. In the area of CAD/CAE/CAM applications, an information gap exists between design models and analysis models. To this end, a multi-representational architecture (MRA) is presented to facilitate the transformation of information from design models to various support analysis models. In this paper, our primary focus is on ABBs (Analysis Building Blocks) for solid mechanics and thermal systems that generate FEA (Finite Element Analysis) SMMs (Solution Method Models) to obtain their results. Our focus in this paper is to investigate the effectiveness of the Pahl and Beitz methodology in developing the ABB information model. The Pahl and Beitz design methodology is intended for physical product design applications. Three of the four phases of the Pahl and Beitz methodology are examined and modified to facilitate development of the ABB information model. The augmentations of these phases are presented in this paper. The results of the development of concepts of ABB information model using the Pahl and Beitz methodology support the use of systematic design methodologies for the development of information models. The emphasis of this work is on the methodology used to develop the ABB information model rather than the technical result of the ABB model.

Purpose Automatic mesh generation is still a challenge problem for combustion fluid dynamics simulations because of the high-quality requirement and complexity of geometries. This paper aims to find an efficient automatic analysis model creation and mesh generation method to save the time for pre-processing in numerical simulations. Design/methodology/approach Based on the previous work, we explore effective model processing and mesh generation methods from practical engineering applications. Considering the automation and high quality requirement, we construct an automatic mesh generation procedure for combustion fluid dynamics problems. Findings The numerical results show that the procedure we proposed in this paper can automatically generate high quality mesh for combustion fluid dynamics simulations. The strategy of fluid model construction is time-saving and with high-precision. The mesh generation method in our procedure is automatic and efficient. Practical implications The procedure proposed in this paper is applicable to the practical engineering application model, such as aircraft simulation, aeroengine simulation and so on. The procedure has been integrated into an numerical simulation software. Originality/value The method proposed in this paper has very practical application value. It can be used in the practical application and saves a lot of manual processing time for numerical stimulation specialists.

Subdivision methods have been mainly used in computer graphics. This paper extends their applications to the integration of geometric design and Finite Element Analysis (FEA) for sheet metal structures, and fulfils the seamless integration of geometric design and FEA in the model and representation. A common model or a unified representation for geometric design and FEA was created with subdivision surfaces for sheet metal structures. Automatic mesh generation for geometric design and FEA was fulfilled through subdivision methods. The seamless integration can improve the accuracy in numerical analysis and shorten the cycle for the geometric design and the FEA of sheet metal structures.

Winding number based automatic mesh generation algorithm for hydrogen analysis code GASFLOW-MPI

Scale-resolving simulations possess considerable benefits over modeled approaches because of their ability to access the underlying nonlinear fluid dynamics, and thus to predict not only the correct phenomenology, but also to generate insights on strategies to mitigate or eliminate undesirable features. The expense of resolving all pertinent turbulent scales becomes prohibitive however, as the size of the problem, typically measured by the Reynolds number based on a suitable set of reference parameters, becomes large, as is the case with flows of industrial interest such as full aircraft or their complex subsystems. This paper provides an assessment of scale-resolving methods, including some of the main benefits as well as barriers for use on large problems, together with a perspective on historical and recent trends that appear promising in the quest for routine industrial use. The factors that constitute the biggest hurdles to achieving acceptable wall-clock times and costs include meshing of complicated geometries, numerical schemes that are robust as well as accurate, suitable initial and boundary conditions, economical yet appropriate representation of near-wall turbulence, code parallelism, scalability and portability, and post-processing of the resulting big datasets. Considerations for these interrelated aspects are highlighted in the context of several 3D problems of increasing complexity, from wing sections without and with sweep, to aircraft wakes, propulsion subsystems, scramjet flowpaths and finally, full aircraft including empennages. Collectively, these examples feature the benefits of scale-resolving simulations. An illustrative approach that has reached a relatively high level of maturity using automatic mesh generation, a non-dissipative yet robust scheme, wall-modeling of turbulence, superior scalability and requiring little user intervention beyond providing the surface model, is used to demonstrate the potential of scale-resolving simulations for industry, achievable at modest cost and in reasonable wall-clock time.