scholarly journals Analysis of Generic IGBEM for Lifting Hydrofoils

2020 ◽  
Vol 3 (3) ◽  
pp. 205-215
Author(s):  
Aleksander Grm
Keyword(s):  
Mesh Generation ◽  
Isogeometric Analysis ◽  
Degrees Of Freedom ◽  
Design Stage ◽  
Crucial Aspect ◽  
Hydrodynamic Properties ◽  
Galerkin Approach ◽  
Nurbs Basis Function ◽  
Vessel Resistance ◽  
Method Accuracy

Today the most crucial aspect in the preliminary vessel design stage is to make it as green/blue as possible. One of the exciting goals is the minimisation of vessel resistance. The use of hydrofoils to reduce the vessel draught and consequently, reduction in the vessel resistance is today one of the hottest design topics, especially for catamaran passenger vessels. In the present work, we discuss the issues related to the implementation of Isogeometric Analysis (IGA) Boundary Element Method (BEM) for the calculation of the hydrodynamic properties of lifting hydrofoils. The use of IGBEM allows numerical calculation of foil hydrodynamic properties without the traditional step of mesh generation using the CAD geometry directly. The analysis relies on the NURBS basis function with the generic Galerkin approach allowing identical solutions procedures for 2D or 3D problems. Method accuracy and computational times for a different number of Degrees of Freedom (DOF) in 2D are investigated.

scholarly journals Implementation of dimensional management methodology and optimisation algorithms for pre-drilled hinge line interfaces of critical aero assemblies – A case study

2020 ◽  
pp. 095440542097810
Author(s):  
Konstantinos C Bacharoudis ◽  
David Bainbridge ◽  
Alison Turner ◽  
Atanas A Popov ◽  
Svetan M Ratchev
Keyword(s):  
Degrees Of Freedom ◽  
Engineering Problem ◽  
Hole Diameter ◽  
Design Stage ◽  
Assembly Process ◽  
Mechanical Assembly ◽  
Hinge Line ◽  
Management Procedure ◽  
Dimensional Management ◽  
Optimisation Algorithms

A dimensional management procedure is developed and implemented in this work to deal with the identification of the optimum hole diameter that needs to be pre-drilled in order to successfully join two subassemblies in a common hinge line interface when most of the degrees of freedom of each subassembly have already been constrained. Therefore, an appropriate measure is suggested that considers the assembly process and permits the application of optimisation algorithms for the identification of the optimum hole diameter. The complexity of the mechanical subassemblies requires advanced 3D tolerance analysis techniques to be implemented and the matrix method was adopted. The methodology was demonstrated for an industrial, aerospace engineering problem, that is, the assembly of the joined wing configuration of the RACER compound rotorcraft of AIRBUS Helicopter and the necessary tooling needed to build the assembly. The results indicated that hinge line interfaces can be pre-opened at a sufficiently large size and thus, accelerate the assembly process whilst the suggested methodology can be used as a decision-making tool at the design stage of this type of mechanical assembly.

Investigation on the Robustness of Rotor/Stator Contact Interactions with Respect to Small Mistuning

2021 ◽  
Author(s):  
Florence Nyssen ◽  
Alain Batailly
Keyword(s):  
Degrees Of Freedom ◽  
Design Stage ◽  
Contact Interactions ◽  
Reduced Basis ◽  
Amplification Factors ◽  
Bladed Disk ◽  
Nonlinear Amplification ◽  
Rotor Stator Interaction ◽  
Bending Modes ◽  
The Impact

Abstract In this work, the impact of small mistuning on rotor/stator contact interactions is investigated. First, a detailed study of a rotor/stator interaction between the first bending modes and the second engine order is presented in the tuned case. Then, a numerical investigation on the effect of mistuning on the studied rotor/stator contact interaction is carried out. In particular, a stochastic analysis is performed to evaluate the robustness of the interaction with respect to the mistuning level. Simulations are conducted using a reduced order model (ROM) of an industrial bladed disk that combines both physical degrees of freedom (along blades tip for contact treatment) and modal coordinates. Mistuning is introduced in the tuned ROM by means of a modified version of the component mode mistuning method that allows to keep physical degrees of freedom within the reduced basis. Nonlinear amplification factors, i.e. the amplification factors in the context of contact nonlinearities, are compared with their linear counterparts, the latter are computed using a linear forcing on each blade using a two nodal diameters traveling wave excitation on the mistuned and the tuned bladed disk. The comparison between the linear and nonlinear amplification factor for each sample highlights that no correlation exists between a mistuning pattern leading to high amplifications in a linear context or when contact nonlinearities are taken into account. Therefore, dedicated analyses on the effect of mistuning should be undertaken with contact nonlinearities considerations at the design stage especially if intentional mistuning is considered.

scholarly journals Analog Circuit Design Automation Tool Using Genetic Algorithms

1970 ◽  
Vol 1 (1) ◽  
Author(s):  
Y. M. A. Khalifa ◽  
D. H. Horrocks
Keyword(s):  
Genetic Algorithms ◽  
Circuit Design ◽  
Analog Circuits ◽  
Computer Aided Design ◽  
Degrees Of Freedom ◽  
Analog Circuit ◽  
Search Space ◽  
Design Stage ◽  
Specific Frequency ◽  
Aided Design

An investigation into the application of Genetic Algorithms (GA) for the design of electronic analog circuits is presented in this paper. In this paper an investigation of the use of genetic algorithms into the problem of analog circuits design is presented. In a single design stage, circuits are produced that satisfy specific frequency response specifications using circuit structures that are unrestricted and with component values that are chosen from a set of preferred values. The extra degrees of freedom resulting from unbounded circuit structures create a huge search space. It is shown in this paper that Genetic Algorithms can be successfully used to search this space. The application chosen is a LC all pass ladder filter circuit design.Key Words: Computer-Aided Design, Analog Circuits, Artificial Intelligence.

scholarly journals Space–Time Variational Multiscale Isogeometric Analysis of a tsunami-shelter vertical-axis wind turbine

2020 ◽  
Vol 66 (6) ◽  
pp. 1443-1460 ◽  
Author(s):  
Yuto Otoguro ◽  
Hiroki Mochizuki ◽  
Kenji Takizawa ◽  
Tayfun E. Tezduyar
Keyword(s):  
Unsteady Flow ◽  
Wind Turbine ◽  
Mesh Generation ◽  
Isogeometric Analysis ◽  
Flow Analysis ◽  
Vertical Axis ◽  
Moving Mesh ◽  
Vertical Axis Wind Turbine ◽  
Accurate Representation ◽  
Variational Multiscale

AbstractWe present computational flow analysis of a vertical-axis wind turbine (VAWT) that has been proposed to also serve as a tsunami shelter. In addition to the three-blade rotor, the turbine has four support columns at the periphery. The columns support the turbine rotor and the shelter. Computational challenges encountered in flow analysis of wind turbines in general include accurate representation of the turbine geometry, multiscale unsteady flow, and moving-boundary flow associated with the rotor motion. The tsunami-shelter VAWT, because of its rather high geometric complexity, poses the additional challenge of reaching high accuracy in turbine-geometry representation and flow solution when the geometry is so complex. We address the challenges with a space–time (ST) computational method that integrates three special ST methods around the core, ST Variational Multiscale (ST-VMS) method, and mesh generation and improvement methods. The three special methods are the ST Slip Interface (ST-SI) method, ST Isogeometric Analysis (ST-IGA), and the ST/NURBS Mesh Update Method (STNMUM). The ST-discretization feature of the integrated method provides higher-order accuracy compared to standard discretization methods. The VMS feature addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the blades. The ST-SI enables moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST-IGA enables more accurate representation of the blade and other turbine geometries and increased accuracy in the flow solution. The STNMUM enables exact representation of the mesh rotation. A general-purpose NURBS mesh generation method makes it easier to deal with the complex turbine geometry. The quality of the mesh generated with this method is improved with a mesh relaxation method based on fiber-reinforced hyperelasticity and optimized zero-stress state. We present computations for the 2D and 3D cases. The computations show the effectiveness of our ST and mesh generation and relaxation methods in flow analysis of the tsunami-shelter VAWT.

A Method for the Frequency Domain Seakeeping Analysis of Offshore Structures in the Early Design Stage

2020 ◽  
Author(s):  
Maximilian Liebert
Keyword(s):  
Frequency Domain ◽  
Cross Sections ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Offshore Structures ◽  
Design Stage ◽  
Design Environment ◽  
Early Design ◽  
Early Design Stage ◽  
Response Amplitude Operators

Abstract The motion analysis of floating offshore structures is a major design aspect which has to be considered in the early design stage. The existing design environment E4 is an open software framework, which is being developed by the Institute of Ship Design and Ship Safety, comprising various methods for design and analysis of mainly ship-type structures. In context of the development to enhance the design environment E4 for offshore applications this paper presents a method to calculate the response motions of semi-submersibles in regular waves. The linearised equations of motion are set up in frequency domain in six degrees of freedom and the seakeeping behaviour is calculated in terms of the amplitudes of the harmonic responses. The hydrodynamic forces onto the slender elements of the semi-submersible are accounted for by a Morison approach. As the drag and damping forces depend quadratically on the amplitudes, these forces are linearised by an energy-equivalence principle. The resulting response amplitude operators of the semi-submersible are validated by comparison with model tests. The method represents a fast computational tool for the analysis of the seakeeping behaviour of floating offshore structures consisting of slender elements with circular cross sections in the early design stage.

Isogeometric Stress, Vibration and Stability Analysis of In-Plane Laminated Composite Structures

2018 ◽  
Vol 18 (05) ◽  
pp. 1850070 ◽  
Author(s):  
S. Faroughi ◽  
E. Shafei ◽  
D. Schillinger
Keyword(s):  
Stability Analysis ◽  
Finite Elements ◽  
Isogeometric Analysis ◽  
Composite Structures ◽  
Degrees Of Freedom ◽  
Computational Study ◽  
Laminated Composite ◽  
Basis Functions ◽  
Energy Error ◽  
Laminated Composite Structures

We present a computational study that develops isogeometric analysis based on higher-order smooth NURBS basis functions for the analysis of in-plane laminated composites. Focusing on the stress, vibration and stability analysis of angle-ply and cross-ply 2D structures, we compare the convergence of the strain energy error and selected stress components, eigen-frequencies and buckling loads according to overkill solutions. Our results clearly demonstrate that for in-plane laminated composite structures, isogeometric analysis is able to provide the same accuracy at a significantly reduced number of degrees of freedom with respect to standard [Formula: see text] finite elements. In particular, we observe that the smoothness of spline basis functions enables high-quality stress solutions, which are superior to the ones obtained with conventional finite elements.

A Composite Rigid Body Algorithm for Modeling and Simulation of an Underwater Vehicle Equipped With Manipulator Arms

2004 ◽  
Author(s):  
Mohammad Khalaj Amir Hosseini ◽  
Mohammad Banae ◽  
Ali Meghdari
Keyword(s):  
Rigid Body ◽  
Modeling And Simulation ◽  
Degrees Of Freedom ◽  
Oil And Gas ◽  
Underwater Vehicle ◽  
Underwater Vehicles ◽  
Design Stage ◽  
Viscous Drag ◽  
Position Sensing ◽  
Drag Forces

In this paper modeling and simulation of an underwater vehicle equipped with manipulator arms, using Composite Rigid Body (CRB) algorithm will be discussed. Because of increasing need to Unmanned Underwater Vehicles (UUVs) in oil and gas projects in Persian Gulf, for doing operations such as inspection of offshore jackets, subsea pipelines and submarine cables and also pre installation survey and post laid survey of submarine pipelines and cables, design and construction of “SROV” was developed in Sharif University of Technology, and at design stage behavior of underwater vehicles was studied. In this paper, an efficient dynamic simulation algorithm is developed for an UUV equipped with m manipulators that each of them has N degrees of freedom. In addition to the effects of mobile base, the various hydrodynamic forces exerted on these systems in an underwater environment are also incorporated into the simulation. The effects modeled in this work are added mass, viscous drag, fluid acceleration, and buoyancy forces. For drag forces, the emphasis here is on the modeling of the pressure drag. Recent advances in underwater position and velocity sensing enable real-time centimeter-precision position measurements of underwater vehicles. With these advances in position sensing, our ability to precisely control the hovering and low-speed trajectory of an underwater vehicle is limited principally by our understanding of the vehicle’s dynamics and dynamics of the bladed thrusters commonly used to actuate dynamically-positioned marine vehicles. So the dynamics of thrusters, are developed, and an appropriate mapping matrix dependent on the position and orientation of the thrusters on the vehicle, is used to calculate resultant forces and moments of the thrusters on the center of gravity of the vehicle. It should be noted that hull-propeller and propeller-propeller interactions are considered in the modeling too. Finally the results of the simulations, for an underwater vehicle equipped with one 2 DOFs manipulator, are presented and discussed in details.

A Composite Rigid Body Algorithm for Modeling and Simulation of an Underwater Vehicle Equipped With Manipulator Arms

2005 ◽  
Vol 128 (2) ◽  
pp. 119-132 ◽  
Author(s):  
Mohammad Khalaj Amir Hosseini ◽  
Omid Omidi ◽  
Ali Meghdari ◽  
Gholamreza Vossoughi
Keyword(s):  
Rigid Body ◽  
Modeling And Simulation ◽  
Degrees Of Freedom ◽  
Oil And Gas ◽  
Underwater Vehicle ◽  
Underwater Vehicles ◽  
Design Stage ◽  
Viscous Drag ◽  
Position Sensing ◽  
Drag Forces

In this paper, modeling and simulation of an underwater vehicle equipped with manipulator arms, using a composite rigid body algorithm, will be discussed. Because of the increasing need for unmanned underwater vehicles (UUVs) in oil and gas projects in the Persian Gulf, for doing operations such as inspection of offshore jackets, subsea pipelines, and submarine cables, and also pre-installation survey and post-laid survey of submarine pipelines and cables, design and construction of “SROV” was developed in Sharif University of Technology, and at the design stage behavior of the underwater vehicles was studied. In this paper, an efficient dynamic simulation algorithm is developed for an UUV equipped with m manipulators so that each of them has N degrees of freedom. In addition to the effects of the mobile base, the various hydrodynamic forces exerted on these systems in an underwater environment are also incorporated into the simulation. The effects modeled in this work are added mass, viscous drag, fluid acceleration, and buoyancy forces. For drag forces, the emphasis here is on the modeling of the pressure drag. Recent advances in underwater position and velocity sensing enable real-time centimeter-precision position measurements of underwater vehicles. With these advances in position sensing, our ability to precisely control the hovering and low-speed trajectory of an underwater vehicle is limited principally by our understanding of the vehicle’s dynamics and the dynamics of the bladed thrusters commonly used to actuate dynamically positioned marine vehicles. So the dynamics of thrusters are developed and an appropriate mapping matrix dependent on the position and orientation of the thrusters on the vehicle is used to calculate resultant forces and moments of the thrusters on the center of gravity of the vehicle. It should be noted that hull-propeller and propeller-propeller interactions are considered in the modeling too. Finally, the results of the simulations, for an underwater vehicle equipped with 1 two degrees of freedom manipulator, are presented and discussed in detail.

Dynamic Analysis of Elastic Structures on Spreadsheet

2012 ◽  
Author(s):  
J.-M. Rambach
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Modal Analysis ◽  
Safety Assessment ◽  
Degrees Of Freedom ◽  
Vertical Plane ◽  
Design Stage ◽  
Margin Assessment ◽  
Sensitivity Studies ◽  
Stick Model

It is recalled the interest of modal analysis of heavy structures on stick model with reduced number of degrees-of-freedom (DOF), at every age of the structure: at the presizing stage, at the design stage, for assessing the results given by large tridimensional Finite Element (FE) models, and at every further seismic review (Seismic Margin Assessment studies, Seismic Probabilistic Safety Assessment studies). This article indicates a practical means for a simple programing of a modal analysis based FE code on spreadsheet able to handle up to 50 DOF. The beams, of Timoshenko’s type, are supposed moving along a vertical plane, with 2 DOF per node: the horizontal translational DOF and the rotational DOF around the horizontal axis perpendicular to the vertical plane. The analysis follows the classical steps of any FE code. The programing of such dynamic modal analysis on a spreadsheet is besides quite easy and provides a very convenient tool i) for the intimate understanding of the dynamic behavior of structures ii) for any accurate modal analysis and iii) for any sensitivity studies.

Reduced-Order P.O.D. Models for Nonlinear Vibrations of Cylindrical Shells

2003 ◽  
Author(s):  
M. Amabili ◽  
A. Sarkar ◽  
M. P. Pai¨doussis
Keyword(s):  
Time Series ◽  
Degrees Of Freedom ◽  
Cylindrical Shells ◽  
Harmonic Excitation ◽  
Computational Effort ◽  
Inviscid Fluid ◽  
Galerkin Approach ◽  
System Behaviour ◽  
Proper Orthogonal Modes ◽  
Proper Orthogonal

The nonlinear (large-amplitude) response of perfect and imperfect, simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of some of their lowest natural frequencies is investigated. The shell is assumed to be completely filled with an incompressible and inviscid fluid at rest. Donnell’s nonlinear shallow-shell theory is used, and the solution is obtained by the Galerkin method. The proper orthogonal decomposition (POD) method is used to extract proper orthogonal modes that describe the system behaviour from time-series response data. These time-series have been obtained via the conventional Galerkin approach (using normal modes as a projection basis) with an accurate model involving 16 degrees of freedom, validated in previous studies. The POD method, in conjunction with the Galerkin approach, permits a lower-dimensional model with respect to the conventional Galerkin approach. Different proper orthogonal modes computed from time-series at different excitation frequencies are used and solutions are compared. Some of these modes are capable of describing the system behaviour over the whole frequency range around the fundamental resonance with good accuracy and with only three degrees of freedom. They allow a drastic reduction in the computational effort, as compared to using the 16 degrees-of-freedom model necessary when the conventional Galerkin approach is used.

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