Open Cascade 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.

Investigating transfer of coherence, direction of light propagation and Rydberg blockade in a four-level [formula omitted]-type system under linear and nonlinear interaction regimes

This theoretical study reveals that the transfer of coherence (TOC) and the direction of light propagation vector play a crucial role in transitioning from electromagnetically induced transparency (EIT) to electromagnetically induced absorption (EIA) in a four-level closed and open cascade (Ξ)-type light-atom interacting systems (LAIS) under both linear as well as nonlinear interaction regimes. It is found that the amplitudes of the coherence signals are distinctly influenced by the system’s openness driven by the presence of additional dipole allowed levels not connected by the lasers and the type of interaction regimes. The effect of TOC on the EIT to EIA transition is discussed in detail by the velocity-dependent dressed state analysis and velocity mapping of the probe absorption coefficient. The findings also reveal that the efficiency of the counter-propagation scheme of the coupling fields is higher than the co-propagation scheme. Furthermore, we have estimated the Rydberg blockade effect on the probe absorption profiles for some specific velocity groups of atoms, which exhibit probe gain in the medium along with EIT and EIA patterns.

Construction and application of online parametric modeling platform for face milling cutters based on WebGL and Open CASCADE

The secondary development of traditional commercial CAD/CAE software has been widely used in the process of cutting tools design and optimization. However, limited by copyright and hardware configuration, the effect of this development is limited, and the secondary development can no longer meet the needs of rapid and accurate cutting tools design. With the rapid development of Internet, online cutting tools CAD software based on Web has become a new development direction with its characteristics of specialization and lightweight. In order to build an online cutting tools CAD software, an online parametric design platform for indexable face milling cutters is established based on Web development technology, Open CASCADE and Three.js. The platform can quickly generate a 3D basic model for NC machining programing and a 3D detailed model for finite element simulation of cutting process according to ISO 13399. Based on the built platform, the finite element simulation model of cutting process of indexable surface milling cutter is established. The establishment of the model can play an important role in improving the design efficiency and reducing the design cost for the optimal design of this kind of milling cutter.

Development and application of parametric design system for solid end mills based on Open CASCADE

Development and application of parametric design system for solid end mills based on Open CASCADE

Evaluation of hemodynamic significance for paraprosthetic fistula after transcatheter aortic valve implantation

Highlights. Using ECHO and MSCT data, a numerical assessment of hemodynamic effects of paraprosthetic regurgitation following transcatheter aortic valve replacement was performed. A significant increase in the fluid flow, wall and viscous shear stresses in the area of regurgitation is shown. The modeling technique described in the paper can be used prospectively in assessing the optimal treatment modality in terms of predicting the quantitative characteristics of the flow, associated with the risks of destruction of red blood cells and thrombosisAim. To make a numerical assessment of hemodynamic effects of paraprosthetic regurgitation following transcatheter aortic valve replacement based on retrospective clinical data.Methods. The study included echocardiography and multi-slice computed tomography data as input data for modeling one pulsation of a fluid similar in properties to blood. Reconstruction of the paraprosthetic fistula and the ascending aorta was performed in the Mimics medium (Materialise, Belgium). The obtained 3D models were processed in the Salome software (OPEN CASCADE SAS, France), after which they were exported to HELYX-OS (ENGYS, Great Britain) to build a finite element mesh. The flows were modeled using the OpenFOAM software package version 6 (The OpenFOAM Foundation Ltd, UK).Results. The simulation result, expressed quantitatively and qualitatively in the form of diagrams of the measured parameters – fluid flow velocities, wall and viscous shear stresses, shows a significant increase in indicators in the area of paraprosthetic regurgitation. Thus, the velocity in the affected area was 1.9–4.2 m/s, which is 3.8 higher than the average value in the entire computational area. The wall shear stress value was up to 61 Pa in the critical area, which may indicate an increased risk of thrombus formation due to the initiation of the clotting cascade through the von Willebrand factor. The value of viscous shear stress, the main component of the destruction of red blood cells in laminar flow, amounted to 20–26 Pa, which, in general, is not enough for mechanical hemolysis.Conclusion. The modeling technique described in the paper can be used prospectively in assessing the optimal treatment modality in terms of predicting the quantitative characteristics of the flow, associated with the risks of destruction of red blood cells and thrombosis.

An evaluation of concordance between linear measurements obtained from conventional, digital and reconstructed three-dimensional printed orthodontic models: An in vitro study

Abstract Objective: To evaluate the potential use of digital and reconstructed three-dimensional printed models as an alternative to conventional plaster models by assessing the accuracy of their linear measurements. Methodology: Pre-treatment plaster models of 45 patients were selected from the archives of the Department of Orthodontics. Each physical plaster model was scanned and digitized using a three-dimensional (3D) laser surface scanning system (inEOS X5, Dentsply Sirona, Bensheim, Germany). The scanned STL files were later used to reconstruct models by 3D printing using Figure4® standalone 3D printer (3D systems, Rock Hill, South Carolina). Measurements of teeth 11 and 16, the transverse width of the upper jaw between the first molars (MM - intermolar width) and canines (CC - intercanine width) were done manually using a digital vernier caliper (Mitutoyo, Kawasaki, Japan), and the CAD Assistant software (Open cascade, Guyancourt, France). Intra examiner data, Intraobserver variability, and measurement accuracy were evaluated using Intraclass Correlation Coefficient (ICC) analysis was done using SPSS 20.0. Results: The intraclass correlation coefficients were >0.8 indicating high reproducibility and reliability. Significant differences were found between the physical and the digital models but to a small proportion which were deemed not clinically relevant. Conclusion: Both the digital models and reconstructed three-dimensional printed models using Figure4® technology were clinically permissible in terms of accuracy and reproducibility. The digital storage, transmission, and treatment planning in an environmentally friendly manner should promote digital over conventional records.

An open-source framework for coupling non-matching isogeometric shells with application to aerospace structures

We introduce an open-source framework to directly analyze aerospace structures represented as collections of untrimmed NURBS patches, which is the representation used by NASA's Open Vehicle Sketch Pad (OpenVSP) for aircraft conceptual design. Airframes are modeled mechanically as Kirchhoff–Love shells and discretized isogeometrically for computational analysis. Coupling between separately-parameterized patches uses a slight modification of the penalty formulation proposed by Herrema et al. (2019) [31], which we verify using a similar suite of benchmark problems. Our open-source implementation leverages both advanced code generation through the FEniCS toolchain and efficient computational geometry operations through the Open Cascade modeling kernel. To demonstrate the framework's applicability to complicated industrial geometries, we perform stress analysis of the wing of an eCRM-002 electric vertical takeoff and landing (eVTOL) aircraft, with skin geometry designed in OpenVSP and internal stiffener geometry generated by an auxiliary tool. Source code for our non-matching shell analysis library PENGoLINS (PENalty-based GLuing of Isogeometric Non-matching Shells) will be maintained at https://github.com/hanzhao2020/PENGoLINS.

An Open-Source Processing Pipeline for Quad-Dominant Mesh Generation for Class-Compliant Ship Structural Analysis

We present an algorithm for the fully automatic generation of a class-compliant mesh for ship structural analysis. Our algorithm is implemented as an end-to-end solution. It starts from a description of a geometry and produces a class conforming surface mesh as a result. The algorithm consists of two parts, the automatic geometry refinement and the preconditioned Delaunay frontal quad dominant mesh generator. A geometry is described by a dictionary of elements and it contains points, rods, plates, and openings. A dictionary can contain modeling errors such as unintended overlaps or an unintended loss of connectivity between elements. The main contribution of the paper is the automatic geometry refinement algorithm and the virtual stiffener procedure designed to control the local mesh orientation of a marching front meshing algorithm. The geometry refinement algorithm guarantees that the output dictionary will be such that intersections of the boundary edges of plates are guaranteed to be nodes of any mesh generated by tessellating such geometry. The algorithm is implemented in Python, using the open-source Gmsh system together with the Open CASCADE kernel which is used to implement the automatic geometry refinement. We present several benchmark models from an engineering practice to illustrate our claims as well as to benchmark the efficiency of the various stages of the processing pipeline.

Automatic cabin virtualization based on preliminary aircraft design data

Preliminary aircraft design and cabin design are essential and well-established steps within the product development cycle for modern passenger aircraft. In practice, the execution usually takes place sequentially, with the preliminary design defining a basic cabin layout and the detail implementation following in a subsequent step. To enable higher fidelity assessment of the cabin early in the design process—for example by means of virtual reality applications—this paper proposes an interface, which can derive detailed 3D geometry of the fuselage from preliminary design data provided in the Common Parametric Aircraft Configuration Schema (CPACS). This is a key step towards integration of cabin analysis and preliminary design in automated collaborative aircraft design chains, not only in terms of passenger comfort, but also manufacturability or crash safety. Like the TiGL Geometry Library for CPACS, the interface presented acts as a parameter engine, which translates data from CPACS into CAD geometry using the Open Cascade Technology library. However, the scope of TiGL is expanded significantly, albeit with an explicit focus on the fuselage, by including more details such as extruded frame and stringer profiles and floor structures. Furthermore, advanced knowledge management techniques are employed to detect and augment missing data. For virtual reality applications, triangulated representations of the CAD geometry can be provided in established exchange formats, creating an interface to common visualization platforms. Additionally, a new evolution of the cabin definition schema in CPACS is presented, to incorporate models of cabin components such as seats or sidewall panels enabling immersive virtual mock-ups.

Организация технических условий и информационных данных в 3D моделях программных систем

The article discusses issues related to the introduction of additional engineering information into the digital model of the product. It is known that technical conditions and dimensions are an integral part of any drawing, and the expansion of the possibilities for presenting engineering data as part of a digital model allows you to get rid of drawing documents. Most software systems for enterprises use the specified functionality in models, but the transfer of data (models and technical conditions in them) is difficult between systems. An example is exporting data from NX CAD to Solid Works. The proposed solutions in this article make it possible to transfer the technical conditions and the required model by means of a software solution and developed methods based on the functionality of the geometric kernel of Open Cascade.

Разработка автономных программных решений на основе геометрических ядер по созданию цифровых сборочных моделей станочных приспособлений

The article discusses approaches and solutions aimed at increasing the productivity of engineering departments, where CAD software solutions are actively used. In the manufacture of machine parts, it becomes necessary to design technological equipment. Elements of machine tools can be prepared and placed in electronic catalogs (libraries), which in an automated mode will create a set of parametric models of the required technological equipment of machine tools. In this case, the accuracy and quality of modeling will be achieved by excluding the human factor from the design process. The development of such software solutions is implemented by means and components of the open geometric kernel Open Cascade, which has great potential both in the field of modeling and scientific computing.

Visualization of metalworking processes in the development of simulation programs for equipment with numerical control

The article proposes the concept and implementation of soft-ware solutions that allow to present milling and turning processes. The software simulates metal-looping using a pre-created control program in G-code. Software products based on the use of functional capabilities of the open Cascade geometric core allow not only to visualize the processes of milling and machining, but also to transfer models with the results of processing through export formats to other CAD systems.

Development of autonomous software solutions based on geometric cores to create digital assembly models of machine tools

The article considers approaches and solutions aimed at improving the productivity of engineering departments, where CAD software solutions are actively used. In the manufacture of parts of machinery there is a need in the design of tooling. Elements of machine tools can be prepared and distributed in electronic libraries, which in an auto-mated mode will create a set of parametric models of the required tooling of machine equipment. The accuracy and quality of modelling will be achieved by eliminating the human factor from the design process. The development of such software solutions is implemented by means and components of the open geometric kernel Open Cascade, which has great potential in the field of modelling and scientific calculations.

Development of an assistant program for CAD-to-cosRMC modelling

Abstract cosRMC is a three dimensional neutron photon transport Monte Carlo code based on the stochastic statistical method of neutral particle transport. At present, the cosRMC geometry model is imported by writing the input file manually, which leads to time-consuming, inefficient and error-prone problems. This will limit application of cosRMC in fusion neutronics calculations because of the complex geometry in fusion devices. Therefore, in order to improve the modeling efficiency and meet the requirements of calculation and analysis of advanced nuclear facilities, a visual modeling platform, cosVMPT—Visual Modeling Platform for Particle Transport, is developed based on Open Cascade (OCC) as CAD geometry engine and FreeCAD framework as graphical user interface. This platform can realize the complete process from modeling to calculation, then to visualization. In this article, the conversion algorithm from CAD models to cosRMC geometry models is introduced in detail. The reliability of the conversion algorithm is preliminarily verified with some representative models by comparing volumes change before and after conversion. The result shows that the geometries after conversion are in good consistency with the original geometries.

FormPATCH - Forming of Complex Composite Structures using Patching Technologies

Fiber-reinforced plastics parts produced in medium or large quantities can be manufactured by forming flat textile fabrics to a component contour. Due to the stiffness of fibrous semi-finished products, forming of complex geometries with an uncut fabric is not always possible. Various effects in the fabric structure can occur, that affect the function or design of the final component. Therefore, patch placement of cut fabrics is a common way to build complex geometries. Usually, fewer and larger patches lead to a more economical process as handling steps can be reduced.This paper presents an optimization algorithm for large patch geometries. A possibility to simulate fabric forming and resulting shear deformations is the fast, but approximate, kinematic method. We use state of the art kinematic simulation approaches and enhance them for our purposes with integration in an optimization process. The optimization objective is to generate as few patches as possible to cover the entire geometry. For the simulation, different positioned and randomly distributed starting points are generated that lead to different patches. The algorithm uses Open Cascade’s Computer Aided Design (CAD) libraries and a Qt user interface (library for cross-platform graphical user interfaces). After importing CAD parts, users can run the patch optimization algorithm, or alternatively a classic kinematic simulation by selecting a start point, a direction and fabric properties. Each calculated patch is stored locally in a Scalable Vector Graphics (SVG) file. The SVGs contain shear angles at cross-over points of the textile and, furthermore, the surrounding border of a patch. Saving this border in Drawing Interchange Format (DXF) makes it available for CNC cutters. Finally, we demonstrate the proof of concept by the experimental patching of a generic free-form part with three calculated patch geometries.

High‐order curvilinear mesh generation technique based on an improved radius basic function approach

SummaryA high‐order curvilinear hybrid mesh generation technique is developed for high‐order numerical method (eg, discontinuous Galerkin method) applications to improve the accuracy for problems with curve boundary. The grid generation technique is based on an improved radius basic function (RBF) approach by which the straight‐edge mesh is converted into high‐order curve mesh. Firstly, an initial straight‐edge mesh is prepared by traditional grid generation software. Then, high‐order interpolation points are inserted into the mesh entities such as edges, faces, and cells according to the final demand of mesh order. To preserve the original geometry, the inserted points on solid wall are then projected onto the CAD model using an open source tool “Open Cascade.” Finally, other inserted points in the field near the solid wall are moved to appropriate positions by the improved RBF approach to avoid tangled cells. If we use the original RBF approach, then the inserted points on the edge and face entities normal to the solid boundary in the region of boundary layer will move to improper positions. To overcome this problem, a weighting based on the local grid aspect ratio between normal direction and tangential direction is introduced into the baseline RBF approach. Three typical configurations are tested to validate the mesh generator. Meanwhile, a third‐order solution of subsonic flow over an analytical 3D body of revolution in the second International Workshop on High‐Order CFD Methods is supplied by a discontinuous Galerkin solver. These numerical tests demonstrate the potential capability of present technique for high‐order simulations of complex geometries.

NERONE: An Open-Source Based Tool for Aerodynamic Transonic Optimization of Nonplanar Wings

Transonic shape optimization of nonplanar wings is a relevant topic in current aeronautical world. Although widely studied, an appropriate level of robustness and automation is still lacking for the inclusion of aerodynamic shape optimization in a Multi-Disciplinary Optimization (MDO) process. In this paper, a new framework, opeNsource-mEsh-geneRation-fOr-aerodyNamic-Evaluations (NERONE), is presented that allows for an automatic transonic shape optimization process within an MDO loop design using open-source libraries, namely OpenCasCade (OCC) for the geometric description, GMSH for grid generation and SU2 multi-physics for aerodynamic analysis and optimization. Wing geometry is defined in the CPACS standard, converted to a mathematical continuous description (NURBS) and passed to the mesher. Grid generation process is driven by user-defined mesh dimensions defined on wing regions and on support domain boundary surfaces. The aerodynamic analysis and optimization are then launched on the obtained grid. SU2 software has been augmented to overcome robustness issues regarding point-inversion algorithm and to control geometric quality during optimization of nonplanar wings. Capability of NERONE is first demonstrated for 2D Euler and RANS simulations (on the RAE2822 airfoil) and on a 3D Euler case (ONERA M6). With very few user-specified parameters, high-quality grids are obtained providing results that correlate well with the literature data. Finally, NERONE is applied to the local shape optimization of a wing–winglet configuration in transonic flight conditions.

CAD-based robot path planning and simulation using OPEN CASCADE

In manufacturing industries, human operators are required in many manufacturing processes, which is time-consuming and not cost-effective. In the present approach, a CAD-based off-line programming (OLP) platform is developed based on OPEN CASCADE (OCC) open source libraries. The developed platform works as a human-robot interface (HRI), offers friendly interaction in an intuitive way, so that in few minutes with basic information, any user can generate a robot path from a CAD model and visualize the simulation graphically. The platform provides important steps such as loading CAD models to define a task, extracting CAD information to generate a path, checking the reachability of the manipulator, and simulation to check and prevent the possible collision before generating a robot program. To evaluate the industrial usability of the proposed platform, a robot program for gluing application is generated from simulation and mapped to a real 6-Degree Of Freedom industrial manipulator.

PANDORA - A python based framework for modelling and structural sizing of transport aircraft

Over the last years a multidisciplinary aircraft predesign process chain was established at the DLR, including different numerical tools for the modelling and structural sizing of fuselage structures. To improve the flexibility and performance of this structural analysis part in the MDO process a new tool development has been started in 2016 called “Parametric Numerical Design and Optimization Routines for Aircraft” (PANDORA). The PANDORA framework is using the interpreted high-level programming language Python and is focused on using dedicated open-source packages. Within PANDORA a lot of new packages have been implemented, like a new interface to access CPACS data, a python based FE pre- and postprocessor, a FE data converter to build an interface between PANDORA and different FE solver and a visualization interface using “The Visualization Toolkit” (VTK). Some further packages to generate a FE model based on a CPACS file using the geometry core “Open Cascade” (OCC) and a new FE sizing algorithm is also under development. To simplify the usage of PANDORA and to keep it comprehensible - a graphical user interface (GUI) has been added using the PYQT toolkit. In this paper the current state of the PANDORA development is presented and initial applications are shown.

Rapid generation of uniform cellular structure by using prefabricated unit cells

Cellular structures are one of the effective ways to produce parts with higher resource efficiency by reducing material and time used. These complex structures can be built by using Additive Manufacturing (AM) which is hardly achievable by using traditional subtractive manufacturing. Cellular structures can be designed and modelled according to desired, specific properties. However, the modelling can be time and resource consuming, due to the complexity and the size of the structure. This article proposes a modelling technique for rapid generation of cellular structure. The method works based on a concept of a hybrid B-Rep and polygon approach. Prefabrication of unit cell kernels is introduced to shorten time in a populating phase, which results in a significant reduction of modelling time, especially for a structure with a large number of cells. The implementation of this method by using open-source library, Open Cascade Technology (OCCT) and Visualization Toolkits (VTK), is also presented.