Parametric Geometric Model Research Articles

Shape optimization of a blended-wing-body underwater glider using surrogate-based global optimization method IESGO-HSR.

As a novel flying-wing configuration underwater glider, the blended-wing-body underwater glider (BWBUG) has the satisfactory hydrodynamic performance in comparison to the conventional cylindrical autonomous underwater gliders (AUGs). The complicated shape optimization of BWBUG is significant for improving its hydrodynamic efficiency while it has to require huge computation time and efforts. A novel surrogate-based shape optimization (SBSO) framework is proposed to deal with the BWBUG shape optimization problem for improving the optimization efficiency and quality. During the optimization search, the parametric geometric model of the BWBUG is constructed depending on seven specific sectional airfoils, with the planar surface being unaltered. Moreover, an improved ensemble of surrogates based global optimization method using a hierarchical design space reduction strategy (IESGO-HSR) is used for optimizing the chosen sectional airfoils. The optimum shape of BWBUG can be obtained using all sectional airfoils which are successfully optimized. The maximum lift to drag ratio (LDR) of the optimal BWBUG is improved by 24.32% with acceptable computational resources. The optimization results show that the proposed SBSO framework is more superior and efficient in handling the BWBUG shape optimization problem.

Methods of Parametric Geometric Modeling in the Design and Construction of Shells of Gaussian Curvature

The article discusses the method of minimizing costs in the design and construction of spans (shells) with the use of 3D construction printers. The results of the developed program in AutoLISP language for optimizing the surface of a shell of positive Gaussian curvature are presented. The technique of developing a model of a complex projected object for the implementation of a new class of applied problems in the field of additive technologies in construction is presented. The fundamental possibility of the process of extracting and generating new knowledge about the projected object is shown, consisting in replacing it with the corresponding model obtained by formalizing expert information. The construction of mathematical models of complex objects is performed in a fuzzy environment using linguistic variables, fuzzy numbers and arithmetic operations on them. The solution to such problems is based on the application of traditional methods widely used in technical applications to the analysis of fuzzy systems. The mathematical basis of the traditional approach is the algebra of fuzzy numbers.

Features of the use of specialized languages for the construction of geometric models of cellular objects in fi element modeling and optimization calculations

To perform optimization calculations based on the finite element approach in accordance with the criteria accepted by the researcher, it is necessary to first create a parametric geometric model of the product so as to be able to further determine their optimal values by varying the geometric parameters of the project. Since one of the main approaches to the formation of the optimization model is the use of cellular aggregates, the urgent issue is the construction of such geometric objects. The possibility of using the Python language in the SpaceClaim environment to build periodic placeholders is considered. Code fragments and construction results for one of the placeholder types are given. An example of the APDL code for ANSYS of a different type of placeholder is given. The statement of the optimization problem is described and the results of optimization calculations for this placeholder are presented using the example of one construction.

Parametric geometric model of a spherical helical platform

The paper presents a parametric spherical model of a helical surface, which is used in the design of structures of helical platforms. This design is intended to serve the inner surface of spherical tanks. Presentation of the control program using dependent and mathematical models for constructing external and internal contours of the sites.

RATIONALE FOR THE USE OF DOUBLE SHOULDER THREADED CONNECTIONS OF HOLLOW SUCKER RODS

Frequent failures of standard threaded connections of hollow sucker rods are caused by their fatigue failures, self-loosening and leakages. This is mainly caused by such design flaws as unequal load on threads, insufficient shoulder area, stress concentration in the groove, low resistance to bending and torsion loads. Using iterative design, based on parametric geometric modeling and the finite element method, the feasibility of using double shoulder threaded connections for hollow sucker rods has been proved and their design has been improved. The improved connection has two shoulders, modified grooves with an elliptical profile, correction of the first turn of the nipple thread and optimal values of interferences. Due to this, the joint has greater tightness, strength at bending, torsion and compression, higher resistance to self-loosening, more equal load on the threads and greater fatigue strength compared to the standard one. The value of the fatigue safety factor in the area of the first turn of the nipple thread is increased by 13...14, in the area of the last turn of the coupling – by 2.6...4, in the area of the nipple groove by 0…0.4. The use of an elastic element on an additional shoulder allowed increasing the tolerance of the interference on it to 0.2 mm, making it unnecessary to control dimensions before screwing. Even after damage to the elastic part and loss of tension on an additional shoulder, the connection has greater strength than the standard one. In case of rod repairs, improved nipples can be easily implemented by welding them to the rod body. There is also the possibility of implementation of double shoulder cylindrical connections without modifying the standard nipple.

Parametric Geometric Model and Shape Optimization of Airfoils of a Biomimetic Manta Ray Underwater Vehicle

As a new kind of autonomous underwater vehicle, bionic submersible has many merits such as high efficiency and low costs. In order to obtain such advantages, it is a good way to simulate the shapes of marine animals and apply them to the design of artificial underwater vehicle. In this paper, an optimization system of airfoils is proposed by the improved class-shape-transformation (CST) parameterization method and genetic algorithm (GA). The appearance of a manta-ray-inspired underwater vehicle is rebuilt using the optimal sectional airfoils obtained by the proposed optimization system. Computational simulations are carried out to investigate the hydrodynamic performance of the submersible using the commercial computational fluid dynamics (CFD) code Fluent. The results demonstrate that the maximum thickness of the vehicle increases by 9%, which means the loading capacity is increased. Moreover, the underwater vehicle shows better hydrodynamic performance, and the lift-drag ratio of initial design is increased by more than 10% using the presented optimization system of airfoils.

Design and Optimization of a Blended-Wing-Body Underwater Glider

The shape of blended-wing-body underwater glider (BWBUG) is an important factor in determining the hydrodynamic efficiency. In order to reduce the needed computation time and efforts during the search of the optimum shape, a new surrogate-based shape optimization framework is proposed to solve the complicated BWBUG shape design optimization problem in this paper. During the search, seven baseline airfoils are used to build the parametric geometric model of the BWBUG, with the planar surface being fixed. Moreover, a newly proposed ensemble of surrogates based global optimization algorithm using a hierarchical design space reduction method (ESGO-HSR) is employed to optimize each baseline airfoil. Then, the optimum shape of the BWBUG can be determined and rebuilt based on all baseline airfoils that are successful optimized. As the optimization target, the maximum lift to drag ratio of the initial design is increased by 13.72% under the given operating conditions. The results demonstrate that the presented surrogate-based shape optimization framework is efficient and capable in identifying the optimum shape of the BWBUG.

Theoretical analysis of braiding strand trajectories and simulation of three-dimensional parametric geometrical models for multilayer interlock three-dimensional tubular braided preforms

Multilayer interlock three-dimensional (3D) tubular braided composites have been widely used in propeller blades, high pressure pipelines, rocket nose cones and engine nozzles owing to prominent interlaminar shear properties, reliable damage tolerance and outstanding torsion performance. The prediction of the mechanical properties and the design of the fabric structures for the 3D braided composites are dependent on the trajectory distribution of strands and the geometrical model of the braided structure. This paper aims to build theoretical models for the braiding strand trajectories and presents a creative method to establish the parametric geometrical models for the multilayer interlock 3D tubular braided structures. Firstly, mathematical models of braiding strand trajectories are derived based on the analysis for the characteristics of carrier paths, the interlacing and interlocking of braided structures and the motion of braiding strands. The mathematical models are then developed to establish parametric expressions for multilayer interlock 3D tubular braided structures by the advanced development of UG NX®. In addition, the models of corresponding braiding strand trajectories and braiding structures can be obtained automatically in the simulation environment with the modification of design parameters. Finally, the established models are compared with the carbon fiber braided specimen. The results show that the innovative parametric geometric models of the multilayer interlock 3D tubular braided structures accurately describe the key characteristics of the preform.

SCAN-TO-BIM vs 3D IDEAL MODEL HBIM: PARAMETRIC TOOLS TO STUDY DOMES GEOMETRY

Abstract. The contribution is part of an interdisciplinary research that aims to address the problems of knowledge, interpretation and documentation of vulnerable structures such as the brick Renaissance domes in Campania (XV-XVI century). The goal is to analyze the relationship between Survey, Historic Building Information Modelling (HBIM) and 3D parametric models based on geometric rules from Treaties to study and to manage Cultural Heritage. HBIM is generally based on scan-to-BIM process that allows to generate 3D model from point cloud. The reverse modeling process, from a point cloud to parametric geometric model, poses a series of issues at the center of cultural debate that currently takes place around HBIM. The experimentation underway is part of this research field with the aim of using the parametric approach as a tool able to introduce an additional methodology for big data interpretation. Currently we can identify two different approaches for the construction of a HBIM system: building a simplified model by identifying the shape grammar or building the geometric components from survey without using pre-compiled objects libraries, following the scan to BIM logic. In our research we are going to identify an "hybrid" methodology. Generally the process is based on the knowledge and critical abilities of individual scholars, the idea is to increase the efficiency of the system through collaborative workflow forms that allow to optimize the processes through effective knowledge management actions. We are going to use procedural modeling techniques to generate HBIM domes library.

Simulation of an aerodynamic profile with sections of ad hoc concavity

The article describes the study carried out by the authors of the use of parametric geometric models to reduce the complexity of the design of parts that follow the theoretical contour of the bearing surfaces of the aircraft. Also, an algorithm that allows eliminating the existing ad hoc concavity profile is considered.

Computer variant dynamic forming of technical objects on the example of the aircraft wing

This article describes a mathematical apparatus of dynamic formation of technical objects on the basis of a study that has devised it with the aim to improve and develop computerized structural and parametric geometric models by appropriate integration with their available mathematical support. The practical value of the obtained results consists in creating a methodology for computer variant dynamic shaping, which helps flexibly combine the designing and manufacturing of technical objects, as is illustrated by the example of the wing of an aircraft. The proposed techniques provide an automated design of the wing surface and a computer simulation of such technological operations for manufacturing a centreplane longeron as cutting, pressure treatment, assembly, etc. The created structural and parametric geometric models contribute to the multicriteria optimization of technical objects throughout the lifecycle. The described approach can also be used for the computer variant dynamic formation of such structural units of the airframe as ribs, panels, sections, bends, and the like. Through further studying, the research materials can be distributed to diverse products of mechanical engineering and other industries

Parametric geometric model and hydrodynamic shape optimization of a flying-wing structure underwater glider

Combining high precision numerical analysis methods with optimization algorithms to make a systematic exploration of a design space has become an important topic in the modern design methods. During the design process of an underwater glider’s flying-wing structure, a surrogate model is introduced to decrease the computation time for a high precision analysis. By these means, the contradiction between precision and efficiency is solved effectively. Based on the parametric geometry modeling, mesh generation and computational fluid dynamics analysis, a surrogate model is constructed by adopting the design of experiment (DOE) theory to solve the multi-objects design optimization problem of the underwater glider. The procedure of a surrogate model construction is presented, and the Gaussian kernel function is specifically discussed. The Particle Swarm Optimization (PSO) algorithm is applied to hydrodynamic design optimization. The hydrodynamic performance of the optimized flying-wing structure underwater glider increases by 9.1%.

Spline Parameterization of Complex Planar Domains for Isogeometric Analysis

Abstract Isogeometric Analysis (IGA) involves unification of modelling and analysis by adopting the same basis functions (splines), for both. Hence, spline based parametric model is the starting step for IGA. Representing a complex domain, using parametric geometric model is a challenging task. Parameterization problem can be defined as, finding an optimal set of control points of a B-spline model for exact domain modelling. Also, the quality of parameterization, too has significant effect on IGA. Finding the B-spline control points for any given domain, which gives accurate results is still an open issue. In this paper, a new planar B-spline parameterization technique, based on domain mapping method is proposed. First step of the methodology is to map an input (non-convex) domain onto a unit circle (convex) with the use of harmonic functions. The unique properties of harmonic functions: global minima and mean value property, ensures the mapping is bi-jective and with no self-intersections. Next step is to map the unit circle to unit square to make it apt for B-spline modelling. Square domain is re-parameterized by using conventional centripetal method. Once the domain is properly parameterized, the required control points are computed by solving the B-spline tensor product equation. The proposed methodology is validated by applying the developed B-spline model for a static structural analysis of a plate, using isogeometric analysis. Different domains are modelled to show effectiveness of the given technique. It is observed that the proposed method is versatile and computationally efficient.

A mesh generation method for worn gun barrel and its application in projectile-barrel interaction analysis

Although wear mechanism of gun barrel and projectile-barrel interaction have been comprehensively studied in the past three decades, attention has seldom been paid to the interaction between worn barrel and projectile. In the present work, a new parametric geometric modeling method for gun barrel and a new finite element meshing strategy for the worn barrel are proposed which involve the joint use of Python code and ABAQUS software. A transient coupled thermo-mechanical finite element (FE) model is developed to compute the plastic deformation of rotating band and the performance of interior ballistics. Additionally, material thermal properties of the rotating band are considered and user subroutine VUAMP and VFRICTION are implemented within the FE model in order to take account of the propelling force caused by propellant gas and the effect of changing friction stress, respectively. The FE results obtained in simulation verify the ability of the proposed meshing strategy to improve analysis accuracy with respect to the interaction between the worn barrel and the projectile.

Influencing Parameters of Tip Blowing Interacting With Rotor Tip Flow

The design space of axial-flow compressors is restricted by stability issues. Different axial-type casing treatments (CTs) have shown their ability to enhance compressor stability and to influence efficiency. Casing treatments have proven to be effective, but there still is need for more detailed investigations and gain of understanding for the underlying flow mechanism. Casing treatments are known to have a multitude of effects on the near-casing 3D flow field. For transonic compressor rotors, these are more complex, as super- and subsonic flow regions alternate while interacting with the casing treatment. To derive design rules, it is important to quantify the influence of the casing treatment on the different tip flow phenomena. Designing a casing treatment in a way that it antagonizes only the deteriorating secondary flow effects can be seen as a method to enhance stability while increasing efficiency. The numerical studies are carried out on a tip-critical rotor of a 1.5-stage transonic axial compressor. The examined recirculating tip blowing casing treatment (TBCT) consists of a recirculating channel with an air off-take above the rotor and an injection nozzle in front of the rotor. The design and functioning of the casing treatment are influenced by various parameters. A variation of the geometry of the tip blowing, more specifically the nozzle aspect ratio, the axial position, or the tangential orientation of the injection port, was carried out to identify key levers. The tip blowing casing treatment is defined as a parameterized geometric model and is automatically meshed. A sensitivity analysis of the respective design parameters of the tip blowing is carried out on a single rotor row. Their impact on overall efficiency and their ability to improve stall margin are evaluated. The study is carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) simulations.

An empirical basis for the use of design patterns by architects in parametric design

This article presents the results from exploring the impact of using a parametric design tool on designers’ behavior in terms of using design patterns in the early conceptual development stage of designing. It is based on an empirical cognitive study in which eight architectural designers were asked to complete two architectural design tasks with similar complexity, respectively, in a parametric design environment and a geometric modeling environment. The protocol analysis method was employed to study the designers’ behavior. In order to explore the development of design patterns in the empirical data, Markov model analysis is utilized. Through Markov models analysis of the parametric design environment and geometric modeling environment results, it was found that there are some significantly different design patterns being used when designing in a parametric design environment compared to designing in a geometric modeling environment. The article articulates these differences and draws conclusions from these results.

Parametric geometric model and shape optimization of an underwater glider with blended-wing-body

ABSTRACT Underwater glider, as a new kind of autonomous underwater vehicles, has many merits such as long-range, extended-duration and low costs. The shape of underwater glider is an important factor in determining the hydrodynamic efficiency. In this paper, a high lift to drag ratio configuration, the Blended-Wing-Body (BWB), is used to design a small civilian under water glider. In the parametric geometric model of the BWB underwater glider, the planform is defined with Bezier curve and linear line, and the section is defined with symmetrical airfoil NACA 0012. Computational investigations are carried out to study the hydrodynamic performance of the glider using the commercial Computational Fluid Dynamics (CFD) code Fluent. The Kriging-based genetic algorithm, called Efficient Global Optimization (EGO), is applied to hydrodynamic design optimization. The result demonstrates that the BWB underwater glider has excellent hydrodynamic performance, and the lift to drag ratio of initial design is increased by 7% in the EGO process.

Parametric modeling and comparative finite element analysis of spiral triangular strand and simple straight strand

Spiral triangular strand (STS) and simple straight strand (SSS) are widely used in practical applications, but comparative analyses aimed for a better comprehension of the service behavior are seldom conducted due to the complex geometric configuration of STS. In the present study, a new parametric geometric model of STS, considering the effect of lay angle on the wire cross section, is proposed by means of parametric equations and Pro/Engineer software. Full 3D finite element (FE) models of the STS and SSS are developed with ANSYS software. Under axial tensile and torsional loads, the behaviors of the STS and SSS with the same lay angle and total wire sectional area are comparatively studied, and the comparison are conducted at different lay angles and outer wire diameters. The results of FE analyses show that nonlinear overall behaviors happen to the both kinds of strands. The STS results in smaller axial force and torque, but severer plastic deformation and von Mises stress than the SSS, and the discrepancies increase with increasing lay angle and outer wire diameter. The discontinuous contact lines of the STS lead to the nonuniform distribution of von Mises stress and significant contact pressure.

Imposing angle boundary conditions on B-spline/NURBS surfaces

In this paper, we study the construction of a B-spline surface satisfying prescribed angle distribution (with respect to a chosen vector) of tangent planes along its boundary curve. This problem arises e.g. in a creation of a parametric geometric model of a Pelton turbine bucket, where specific angle distributions along a splitter and an outlet curve have to be fulfilled in order to control the flow of water into and out of the bucket. We prove that for a given B-spline curve c(t), t∈[0,1], the exact solution exists only in very special cases (for a special form of an angle function f(t)). Further, we formulate an algorithm for finding an approximate solution. We also derive a bound on its approximation error and give a numerical evidence that the approximation order of the proposed algorithm is four. Finally, the method is demonstrated on several examples.

Parametric bulbous bow design using the cubic Bezier curve and curve-plane intersection method for the minimization of ship resistance in CFD

Parametric geometric modeling plays an important role in ship’s hull form optimization by use of computational fluid dynamic (CFD) analysis. However, it is difficult to create satisfactory parametric modeling for some curved shapes, such as a ship’s bulbous bow. In this study, the cubic Bezier curve and curve-plane intersection methods are applied to generate the parametric design of a bulbous bow in a solid modeling procedure by taking into account the input of 4 (four) design parameters. For this, a suitable application program interface script within the ANSYS Design Modeler was developed. An application to the ship resistance minimization by use of CFD was made to show that the proposed method could be implemented properly. In this respect, the parametric design of the bulbous bow of a container ship (KRISO Container Ship type) was chosen to be modified. First, it was shown that the computational results generated by CFD were close to the experimental data for the original ship hull form. The developed optimization method was subsequently applied to find the optimal bulbous bow. Finally, the dependence of the optimum bulbous bow on a ship’s speed (some variations of Fn values) was investigated and the results were compared to each other.