Geometry Kernel Research Articles

Knowledge-based model generation for aircraft cabin noise prediction from pre-design data

The climate targets set out in the “European Green Deal” call for the consideration and implementation of climate-friendly propulsion concepts and sustainable fuels in future aircraft configurations. This puts the use of very efficient propeller engines into the focus of aircraft design. However, these pose major challenges, especially to cabin acoustics, due to high, tonal sound pressure levels on the fuselage. The design of noise control measures requires the competence to predict the resulting interior noise as early as possible in the design process of the vehicle. This requires a high level of geometric and structural detail regarding the fuselage structure and cabin components. With increasing frequency range, the necessary structural details also increase, which have to be resolved in the simulation models due to the associated decreasing structural wavelength. Especially in the context of aircraft pre-design, there is usually not enough information available for a detailed vibro-acoustic modeling of the fuselage and cabin components, which allows a meaningful prediction of the vibrations and thus the cabin noise. Therefore, the knowledge-based tool Fuselage Geometry Assembler (FUGA) is developed for the targeted enrichment of preliminary design data with knowledge for detailed numerical analyses. This paper describes the knowledge-based geometry and model generation in FUGA, which can consider the necessary (increasing) level of detail for the vibro-acoustic prediction already in the preliminary design. For this purpose, aircraft data sets in the preliminary design data format Common Parametric Aircraft Configuration Schema (CPACS) form the modeling basis. Originating from the aircraft preliminary design, these initially describe the outer shell of the vehicle and are extended by detailed structural information that defines the geometric boundary conditions for component placement in cabin design. For the cabin components, the open-source geometry kernel Open Cascade Technology (OCCT) is used to provide geometries at the level of detail required for subsequent analyses. The geometry models are then discretized in open source (e.g. Gmsh) or commercial meshers and further used for numerical analysis. Finally, the prediction of cabin noise is demonstrated as a Proof of Concept using the example of a short-haul propeller-driven aircraft and the feasibility of the proposed method is indicated by investigating the sensitivity of resulting simulation models to the fuselage skin thickness.

A Function-Based Approach to Interactive High-Precision Volumetric Design and Fabrication

We present a novel function representation (F-Rep) based geometric modeling kernel tailor-made to support computer aided design (CAD) and fabrication of high resolution volumetric models containing hundreds of billions of voxel grid elements. Our modeling kernel addresses existing limitations associated with evaluating, storing, and accessing volumetric data produced by F-Reps in contexts outside of rendering. The result is an F-Rep modeling kernel well suited for CAD-based applications. Our kernel utilizes a sparse volume data structure to manage F-Rep data while efficient F-Rep evaluation is achieved through a combination of interval arithmetic (IA), just-in-time (JIT) compilation of user-defined functions, and massively parallel evaluation on the GPU. We employ IA as the basis for local pruning of the function evaluation tree to minimize total function evaluations, we use a novel JIT compilation scheme to optimize function execution, and we take advantage of GPU-parallelism to enhance computational throughput. We illustrate the kernel’s effectiveness in visualizing and slicing models with complex defining functions and detailed geometry, and utilize the geometry kernel to manufacture a physical part. Additionally, we present performance metrics across multiple hardware configurations demonstrating significant performance improvements over existing F-Rep geometry kernels, and we examine how our geometry kernel scales with computing power.

Efficient Parallel Optimization for Approximating CAD Curves Featuring Super-convergence

We present an efficient, parallel, constrained optimization technique for approximating CAD curves with super-convergent rates. The optimization function is a disparity measure in terms of a piece-wise polynomial approximation and a curve re-parametrization. The constrained problem solves the disparity functional fixing the mesh element interfaces. We have numerical evidence that when the solver attains a minimum, the constrained disparity preserves the original super-convergence: 2p order for planar curves and ⌊32(p−1)⌋+2 for 3D curves, p being the mesh polynomial degree. Our optimization scheme consists of a globalized Newton method with a nonmonotone line search, and a log barrier function preventing element inversion in the curve re-parametrization. Moreover, we introduce a Julia interface to the EGADS geometry kernel and a parallel optimization algorithm. We test the potential of our curve mesh generation tool on a computer cluster using several aircraft CAD models. We conclude that the solver is well-suited for parallel computing, producing super-convergent approximations to CAD curves.

Computer-aided optimal design for flexible cable in aerospace products based on dynamic analogy modeling

Due to large, complex deformations, the accurate design of cables has become a major problem in the manufacturing of aerospace products. The current design method often leads to large products, uncertain centroids, and poor reliability. To solve these problems, a computer-aided optimal design method for flexible cables was proposed based on dynamic analogy modeling. A nonlinear optimization model was established by combining Cosserat theory and the minimum potential energy principle. The total deformation energy was considered as the optimization object, and Euler parameters were used as control variables to describe the cable geometric shape. Considering the length and bending radius requirements, the normalized form of the cable constraints was expressed by the cross-section position and orientation matrix. An efficient method to solve this problem using finite element discretization and the primitive dual interior point method was proposed. A digital wiring module was developed based on an open source geometry kernel system, and a cable geometry test bench was built. To verify our model, a satellite wiring simulation example was implemented using the module, SolidWorks, and the test bench. Our method achieved the optimal design for the cable length and geometric shape. A theoretical and technical foundation for effectively solving the problem of large cable manufacturing errors and realizing the lightweight design of aerospace products was outlined.

Efficient Pairwise Neuroimage Analysis Using the Soft Jaccard Index and 3D Keypoint Sets.

We propose a novel pairwise distance measure between image keypoint sets, for the purpose of large-scale medical image indexing. Our measure generalizes the Jaccard index to account for soft set equivalence (SSE) between keypoint elements, via an adaptive kernel framework modeling uncertainty in keypoint appearance and geometry. A new kernel is proposed to quantify the variability of keypoint geometry in location and scale. Our distance measure may be estimated between O (N 2) image pairs in [Formula: see text] operations via keypoint indexing. Experiments report the first results for the task of predicting family relationships from medical images, using 1010 T1-weighted MRI brain volumes of 434 families including monozygotic and dizygotic twins, siblings and half-siblings sharing 100%-25% of their polymorphic genes. Soft set equivalence and the keypoint geometry kernel improve upon standard hard set equivalence (HSE) and appearance kernels alone in predicting family relationships. Monozygotic twin identification is near 100%, and three subjects with uncertain genotyping are automatically paired with their self-reported families, the first reported practical application of image-based family identification. Our distance measure can also be used to predict group categories, sex is predicted with an AUC = 0.97. Software is provided for efficient fine-grained curation of large, generic image datasets.

SOLIDUSS: Solid-state diffusion software for radiation protection

The out-diffusion of radionuclides from activated material in case of a fire may represent a non-negligible contribution to the radiological source term of such an event. In order to assess the contribution of this phenomenon, a software package has been designed and implemented. In the present document we briefly introduce the numerical treatment used to tackle the problem prior to the explanation of the software’s logic. The document ends with an exemplary simulation and a study carried out to validate the implementation of the algorithm.The presented tool has been named SOLIDUSS, it is mainly written in C++ and uses a Monte Carlo based approach to simulate the diffusion of radioisotopes within solid materials. It is designed to run coupled with CERN-FLUKA, taking advantage of its geometry kernel to carry out diffusion calculations in arbitrarily complex geometries. The user can provide 3D temperature maps along with many other parameters that allow the program to target a wide range of different scenarios. As results SOLIDUSS provides 3D radionuclide concentration maps as well as the amount of radionuclides out-diffused from the selected materials. So far, this software has undergone numerical validation which will be discussed in this paper. Benchmarking against experimental data is currently ongoing.

Numerical Design for Primary Shaping Manufacturing Processes

AbstractUsing a mold or die, primary shaping manufacturing processes form material from an initially unshaped state (usually melt) into a desired shape. All of these processes have in common that the exact design of the mold cannot be determined directly and intuitively from the product shape. This is due to the non‐linear behavior of the material regarding the flow and solidification processes. Consequently, shape optimization as a means of numerical design can be a useful tool in mold development. The core of our optimization tool is the in‐house flow solver XNS, which is based on the finite element method with GLS stabilization. It is able to exploit the common communication interfaces for distributed‐memory systems. XNS has been coupled with an optimization framework. Furthermore, a geometry kernel has been developed, which internally describes the geometry of the mold in a CAD‐based fashion. The optimization tool has been applied to three melt‐based manufacturing processes: plastics profile extrusion, injection molding and high‐pressure die casting. This paper will focus on injection molding.

Physical deformation configuration of a spatial clamped cable based on Kirchhoff rods

PurposeIn this study, a modeling method for a clamped deformable cable simulation based on Kirchhoff theory is proposed. This methodology can be used to describe the physical deformation configuration of any constrained flexible cable in a computer-aided design/manufacturing system. The modeling method, solution algorithm, simulation and experimental results are presented to prove the feasibility of the proposed methodology. The paper aims to discuss these issues.Design/methodology/approachFirst, Kirchhoff equations for deformable cables are proposed based on the nonlinear mechanics of thin elastic rods, and the general solution of the equations described by the Euler angles is given in the arc coordinate system. The parametric form solution of the Kirchhoff equations, which is easy to use, is then obtained in a cylindrical coordinate form based on Saint Venant’s theory. Finally, mathematical expressions that reflect the clamped cable configuration are given, and the deformable process is simulated based on an open source geometry kernel and is then tested by a 3D laser scanning technology.FindingsThe method presented in this paper can be adapted to any boundary condition for constrained cables as long as the external force and torque are known. The experimental results indicate that both the model and algorithm are efficient and accurate.Research limitations/implicationsA more comprehensive study must be executed for the physical simulation of more complicated constrained cables, such as the helical spring and asymmetric constraint. The influence of the material properties of the cable on the calculation efficiency must be considered in future analysis.Originality/valueThe semi-analytical algorithm of the cable simulation in cylindrical coordinates is a novel topic and is more accurate and efficient than the common numerical solution.

Individualized production in die-based manufacturing processes using numerical optimization

Individualized production, which is a major goal of many high-wage countries, describes a production process in which all elements of a production system are designed in such a way that they enable a high level of product variety at mass production costs. This paper demonstrates recent advances in the individualized production with die-based manufacturing processes, namely high-pressure die casting and plastics profile extrusion. Within these application areas, the chosen approach aiming at individualized production is based on the use of numerical die and process design. The design procedure relies on numerical process simulations based on a nonlinear optimization library and a spline-based geometry kernel. All components interact automatically without requiring user interaction; thus, a completely independent optimization cycle can be achieved. The numerical optimization helps to reduce—or even eliminate—the so far very characteristic manual reworking steps of an original die or process design. These reworking steps are a major cost factor when it comes to individual production. Their abolishment through the presented numerical approaches therefore represents a large step towards the concept of individualized production.

Configuration Modeling and Experimental Verification with 3D Laser Scanning Technology for a Constrained Elastica Cable

For large complex electromechanical products, cable digital design has a problem of low accuracy because of its large deformable characteristics. To solve the problem, an efficacious method is proposed to do cable geometry physical modeling, simulation and test for two-end constrained spatial flexible cables. Euler angles are used as generalized parametric variables to describe cable configuration on the base of Kirchhoff elastic rod theory. Via establishment of a cylindrical coordinate system according to Saint-Venant principle using end constraint, Euler angles’ Analytical solutions of the Kirchhoff equations are gained. Based on an open source geometry kernel system and using numerical integration ideas, a cable configuration simulation platform is developed in C++ environments. Then, a cable geometry measurement bench is founded with the use of 3D laser scan technology. Finally, a cable configuration simulation and experimental example is given to verify the accuracy of the proposed model and relative algorithm, through 3D positional deviation analysis.

Research and Development of Steel Casting CAD/CAE Integration Technology Based on the Neutral STEP File

The casting process CAD system developed based on the existing three-dimensional CAD software has many inadequacies. This paper innovatively puts forward the steel castings three-dimensional casting process CAD system based on neutral STEP file. In this study, by taking advantage of universal CAD data-exchange standard STEP format for data exchange, a practical three-dimensional CAD system was developed based on Open CASCADE Geometry Kernel. The system has the function of practical casting process modeling, including design and modeling of gating system and riser design and so forth. The system exceeded the deficiencies of the existing casting process CAD system. It resolves the foundry Enterprises dependence and limitations on the type and version of commercial 3D CAD software, enabling to realizethe integration of CAD and CAE on casting process.

Development of an Engineering Education Framework for Aerodynamic Shape Optimization

Design optimization is a mathematical process to find an optimal solution through the use of formal optimization algorithms. Design plays a vital role in the engineering field; therefore, using design tools in education and research is becoming more and more important. Recently, numerical design optimization in fluid mechanics, which uses computational fluid dynamics (CFD), has numerous applications in the engineering field, because of the rapid development of high-performance computing resources. However, it is difficult to find design optimization software and contents for educational purposes in aerospace engineering. In the present study, we have developed an aerodynamic design framework specifically for an airfoil, based on the EDucation-research Integration through Simulation On the Net (EDISON) portal. The airfoil design framework is composed of three subparts: a geometry kernel, CFD flow analysis, and an optimization algorithm. Through a seamless interface among the subparts, an iterative design process is conducted. In addition, the CFD flow analysis and the design framework are provided through a web-based portal system, while the computation is taken care of by a supercomputing facility. In addition to the software development, educational contents are developed for lectures associated with design optimization in aerospace and mechanical engineering education programs. The software and content developed in this study is expected to be used as a tool for e-learning material, for education and research in universities.

Research and Development on CAD/CAE Integration of Casting Process System Based on IGES Neutral File

Nowadays, most 3D casting process CAD systems are developed based on second development tools of various 3D CAD systems. However the type and version escalation of various 3D CAD systems in foundry enterprises greatly limit the application of 3D casting process CAD systems. By the data exchange between the neutral file format of 3D geometric model, these problems can be well solved. In this study, by taking advantage of universal CAD data-exchange standard iges for data exchange, a practical 3D CAD system was developed based on opencascade geometry kernel. The system has the function of design and modeling of practical casting process such as part information extraction, parting surface, gating system, riser system and so on. Finally taking a steel casting for example, the casting process is exported in the file of stl and the simulation analysis is carried by intecast software which demonstrate the system based on iges neutral file can well support the integration of casting CAD and CAE.

Numerical shape optimization as an approach to extrusion die design

Profile extrusion is a manufacturing process used for continuous plastic profiles with a fixed cross section. The key challenge in the development of profile extrusion dies is to design the transition region between outflow and inflow of the die in such a way that the material velocity at the outflow is homogeneous. At the current state of the art, die design is experience based and time-consuming running-in experiments need to be performed for each new die. Aim of this work is to develop a new design approach based on numerical shape optimization with the idea of significantly reducing the number of running-in experiments. Based on an existing, in-house flow solver, a shape optimization framework has been established. It contains a geometry kernel, which operates on non-uniform rational B-splines. The framework has been applied to two profile extrusion dies for profiles with rising complexity: a slit profile and a floor skirting. Apart from validating the functionality of the framework, the aim of the test cases was to investigate the influence of the use of the Carreau model on the optimization outcome. From flow simulations, it can be observed that the use of the Carreau model has a definite influence on the resulting flow solution in extrusion die scenarios. However, it is not clear whether this influence extends to the location of the optimal solution.

Product design analysis based on life cycle features

In this research, we effectively integrate the downstream activities of the design process and present a product model representation. Using an extended definition of feature, the product model is represented by its life cycle features, design for X attributes, geometrical and topological information, material features, etc. The relationship between the product features defined makes possible the use of an object-oriented approach to represent the product model with the complete description of the life cycle applications such as the assembly, disassembly, recycling, maintainability, environment, etc. In this way, the designer is able to assess the design performance regarding each life cycle application and redesign the product model accordingly. Since current CAD systems cannot represent the proposed life cycle features, life cycle feature system is implemented using OpenCascade, a geometry kernel and C++ programming. The representation of a product model that integrates the product life cycle features, the geometry and topology of the product and the product model design analysis based on the downstream design activities make our study different from many product design models presented earlier.

A generic lazy evaluation scheme for exact geometric computations

We present a generic C++ design to perform exact geometric computations efficiently using lazy evaluations. Exact geometric computations are critical for the robustness of geometric algorithms. Their efficiency is also important for many applications, hence the need for delaying the costly exact computations at run time until they are actually needed, if at all. Our approach is generic and extensible in the sense that it is possible to make it a library that users can apply to their own geometric objects and primitives. It involves techniques such as generic functor-adaptors, static and dynamic polymorphism, reference counting for the management of directed acyclic graphs, and exception handling for triggering exact computations when needed. It also relies on multi-precision arithmetic as well as interval arithmetic. We apply our approach to the whole geometry kernel of Cgal.

WIENER-HOPF ANALYSIS OF PLANAR CANONICAL STRUCTURES LOADED WITH LONGITUDINALLY MAGNETIZED PLASMA BIASED NORMALLY TO THE EXTRA-ORDINARY WAVE PROPAGATION

The canonical problem of an extra-ordinary Transverse Electromagnetic wave propagating in a parallel plane waveguide with a semi-infinite upper conductor and loaded with magnetized plasma is considered. The homogeneous biasing constant magnetic field is assumed parallel to the substrate and normal to the wave propagation,which incidents normally on the truncated edge. The Wiener-Hopf technique is employed and the corresponding equations are formulated for the open-radiating structure as well as for a closed one resulting from the placement of a metallic shield parallel to the waveguide planes. Closed form field expressions are obtained for the shielded geometry,while the open geometry Kernel factorization is left for future extensions. Important non-reciprocal wave propagation phenomena are involved,which lend non-even function properties to the involved Kernels. Hence,their factorization becomes non-trivial requiring new mathematical approaches. Finally,a review of the involved non-reciprocal and/or unidirectional surface waves is given, which is related to the involved mathematical complexities.

An adaptable and extensible geometry kernel

Geometric algorithms are based on geometric objects such as points, lines and circles. The term kernel refers to a collection of representations for constant-size geometric objects and operations on these representations. This paper describes how such a geometry kernel can be designed and implemented in C ++, having special emphasis on adaptability, extensibility and efficiency. We achieve these goals following the generic programming paradigm and using templates as our tools. These ideas are realized and tested in Cgal, the Computational Geometry Algorithms Library, see http://www.cgal.org/.

JCISE Editorial Board

JCISE Editorial Board

A meshless method for predicting two dimensional flow front advancement and its application in injection moulding

Flow front advancement is a common phenomenon in many industrial process simulations, which are important in designing tools for these processes. The advancement is traditionally simulated by performing numerical computation in a meshed flow domain with a known velocity field. Since the design process is iterative, the costs of performing detail simulation in all iterations are high. This paper presents a meshless approach to simulate the flow front advancement in a bounded domain. The computation efficiency of this approach is raised because part of it is handled by a solid geometry kernel and the costs are further reduced by an estimated the velocity field. The generated flow front pattern is useful in preliminary analysis. An engineering example in injection moulding is raised to demonstrate the application.