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boundary-element-method
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Development of an aeroelastic model based on system identification using boundary elements method
, Article Aircraft Engineering and Aerospace Technology ; Volume 94, Issue 3 , 2022 , Pages 360-371 ; 17488842 (ISSN) ; Borhan Panah, M. R ; Sharif University of Technology
Emerald Group Holdings Ltd
2022
Abstract
Purpose: The purpose of this paper is to analyze the stability of aeroelastic systems using a novel reduced order aeroelastic model. Design/methodology/approach: The proposed aeroelastic model is a reduced-order model constructed based on the aerodynamic model identification using the generalized aerodynamic force response and the unsteady boundary element method in various excitation frequency values. Due to the low computational cost and acceptable accuracy of the boundary element method, this method is selected to determine the unsteady time response of the aerodynamic model. Regarding the structural model, the elastic mode shapes of the shell are used. Findings: Three case studies are...
3D numerical modeling of wave forces on tandem fixed cylinders using the BEM
, Article Journal of Marine Science and Application ; Volume 12, Issue 3 , September , 2013 , Pages 279-285 ; 16719433 (ISSN) ; Abaiee, M. M ; Ahmadi, A ; Sharif University of Technology
2013
Abstract
In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders. The fluid was considered to be inviscid and irrotational. Therefore, the Helmholtz equation was used as a governing equation. The boundary element method (BEM) was adopted to discretize the relevant equations. Open boundaries were used in far fields of the study domain. Linear waves were generated and propagated towards tandem fixed cylinders to estimate the forces applied on them. Special attention was paid to consideration of the effect on varying non-dimensional cylinder radius and distance between cylinders, ka and kd on forces and trapped modes. The...
Three-dimensional scattering of plane harmonic SH, SV, and P waves in multilayered alluvial valleys
, Article Asian Journal of Civil Engineering ; Volume 11, Issue 5 , 2010 , Pages 605-626 ; 15630854 (ISSN) ; Rahimian, M ; Mohammadnejad, T ; Sanaeiha, A ; Sharif University of Technology
2010
Abstract
In this paper, three-dimensional amplification of plane harmonic SH, SV, and P waves in multilayered alluvial valleys is investigated by using a boundary element method in frequency domain. It is shown that in order to achieve real responses, the problem must be analyzed and modeled three-dimensionally. Also, for exact evaluation of surface ground motions in alluvial valleys all key parameters such as layering, material and geometrical characteristics of each layer, stimulation frequency, wave type, plus angle and azimuth of incidence must be taken into account altogether. The accuracy and efficiency of the proposed formulations for the computation of the surface displacement field...
Investigation on behaviors of acoustoelastic cavities using a novel reduced finite element–dual reciprocity boundary element formulation
, Article Engineering Applications of Computational Fluid Mechanics ; Volume 15, Issue 1 , 2021 , Pages 1885-1901 ; 19942060 (ISSN) ; Bornassi, S ; Shen, Y ; Ghalandari, M ; Haddadpour, H ; Firouzabadi, R. D ; Band, S. S ; Chau, K. W ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
This paper presents the acoustic and structure characteristics of chambers with elastic/rigid baffles and elastic walls using a novel formulation. The acoustic fluid is assumed to be compressible and inviscid, and the effect of mean flow is neglected. The acoustic field is formulated based on the dual reciprocity boundary element method (DRBEM), and the finite element method (FEM) is used to model the structural dynamics of elastic walls. The reduced-order model (ROM) of the coupled system is derived based on modal analysis of the acoustic field with rigid boundaries and the structure in a vacuum. Numerical examples are presented, and the acoustic modes and frequencies of the chambers are...
BEM modeling of viscous motion of surface water waves
, Article 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, BC, 20 June 2004 through 25 June 2004 ; Volume 3 , 2004 , Pages 557-561 ; Sharif University of Technology
2004
Abstract
This study is concerned with numerical modeling of viscous surface wave motion using boundary element method (BEM). The equations of motion for thin boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the surface wave motion characteristics including the decay rate. The technique is presented for a standing surface wave motion. The extension to other free surface problems is discussed
Unsteady supersonic aerodynamics based on BEM, including thickness effects in aeroelastic analysis
, Article Journal of Fluids and Structures ; Volume 19, Issue 6 , 2004 , Pages 801-813 ; 08899746 (ISSN) ; Esfahanian, V ; Haddadpour, H ; Behbahani Nejad, M ; Sharif University of Technology
2004
Abstract
A general three-dimensional aeroelastic solver is developed based on coupled finite element and boundary element methods and applied to investigate the flutter boundaries in supersonic flows. The boundary element method is applied to three-dimensional unsteady supersonic potential flow as the aerodynamic model and coupled with the finite element method for structural modelling, in order to construct the system of aeroelastic equations. The aeroelastic equations are solved for the flutter prediction using the frequency domain approach. Flutter boundaries for two types of wing planforms at supersonic speeds are determined and compared with the existing experimental results and previous...
Modeling of a Vague Problem (Floating Breakwater by BEM Analysed) Using ANFIS (Adaptive Neuro-Fuzzy Inference System) and Validation by Fuzzy Boundary Element Method
, M.Sc. Thesis Sharif University of Technology ; Abbaspour Tehrani, Majid (Supervisor)
Abstract
The thesis title is “Modeling of a vague problem (Floating Breakwater by BEM Analysed) using ANFIS (Adaptive Neuro-Fuzzy Inference System) and validation by Fuzzy Boundary Element Method”. In this set of material, more important definitions are described below. When some input data is linguistics, or we have lack of Information or Vagueness, Fuzzy toolbox can alleviate the problem. Fuzzy concept includes several fields and applications like; fuzzy logic, fuzzy sets, fuzzy control, fuzzy arithmetic and fuzzy inference, and the last two applications are used in this thesis. The Neural network is a black box, Neurons that can justify their actions and these artificial brains can grow. The...
Sloshing analysis of flowing liquid in 3D tank using boundary elements method
, Article Journal of Pressure Vessel Technology, Transactions of the ASME ; Volume 135, Issue 2 , 2013 ; 00949930 (ISSN) ; Borhan Panah, M. R ; Sharif University of Technology
2013
Abstract
A numerical model based on the boundary element method is proposed for the sloshing of a flowing liquid in a three-dimensional tank. Assuming a mean flow in the tank in addition to a perturbation flow, the nonlinear boundary conditions of the liquid free-surface are linearized. Using the boundary element method along with the modal analysis technique a reduced order model is obtained which is used to calculate the fundamental sloshing frequencies and modes in the tank with an inlet and outlet. The obtained results for a test case are compared with the literature data to validate the proposed model. The results are in a very good agreement with analytical results and show an acceptable...
Experimental and numerical study of shear crack propagation in concrete specimens
, Article Computers and Concrete ; Volume 20, Issue 1 , 2017 , Pages 57-63 ; 15988198 (ISSN) ; Sarfarazi, V ; Bagher Shemirani, A ; Sharif University of Technology
Abstract
A coupled experimental-numerical study on shear fracture in concrete specimens with different geometries is carried out. The crack initiation, propagation and final breakage of concrete specimens are experimentally studied under compression loading. The load-strain and the strength of the specimens are experimentally measured, indicating decreasing effects of the shear behavior on the failure load of the specimen. The effects of specimen geometries on the shear fracturing path in the concrete specimens are also investigate. Numerical models using an indirect boundary element method are made to evaluate the crack propagation paths of concrete specimens. These numerical results are compared...
Development of an aeroelastic model based on system identification using boundary elements method
, Article Aircraft Engineering and Aerospace Technology ; 2021 ; 17488842 (ISSN) ; Borhan Panah, M. R ; Sharif University of Technology
Emerald Group Holdings Ltd
2021
Abstract
Purpose: The purpose of this paper is to analyze the stability of aeroelastic systems using a novel reduced order aeroelastic model. Design/methodology/approach: The proposed aeroelastic model is a reduced-order model constructed based on the aerodynamic model identification using the generalized aerodynamic force response and the unsteady boundary element method in various excitation frequency values. Due to the low computational cost and acceptable accuracy of the boundary element method, this method is selected to determine the unsteady time response of the aerodynamic model. Regarding the structural model, the elastic mode shapes of the shell are used. Findings: Three case studies are...
Neutron noise simulator based on the boundary element method (BEM)
, Article Annals of Nuclear Energy ; Volume 159 , 2021 ; 03064549 (ISSN) ; Mohamadbeygi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The purpose of the present study is to develop the neutron diffusion solver and neutron noise simulator based on the Boundary Element Method (BEM). The 2-D, 2-G neutron/adjoint diffusion equation and corresponding neutron/adjoint noise equation were solved using the mentioned method. The developed neutron static and noise simulator based on the finite element method gives accurate results when the more number of the elements is used. The motivation of the present research is to use the boundary element method to reduce the computational cost. The boundary element method attempts to use the given boundary conditions to fit boundary values into the integral equation, rather than values...
Three Dimensional Analyses of Binary Lenses
, M.Sc. Thesis Sharif University of Technology ; Rashidian, Bijan (Supervisor) ; Mehrany, Khashayar (Supervisor)
Abstract
Nowadays, Diffractive lenses with the binary profile have extensive application in integrated optics and other areas photonics. These elements-because of their compatibility with integrated circuits fabrication methods- have easy and efficient fabrication processes. They also have low aberration and they offer vast degree of freedom in designing process. The main objective of this thesis is to present an effective method to analyze these binary lenses in three dimensions. From different vectorial analyses methods, Boundary Element Method (BEM) has been chosen because of its different advantages like appropriate precision and higher speed in comparison with other methods. Yet this method has...
Sloshing Analysis of Rectangular Container with Perforated Baffle
, M.Sc. Thesis Sharif University of Technology ; Dehghani Firouzabadi, Rooholah (Supervisor)
Abstract
In this thesis, sloshing of a rectangular container with perforated baffle is being analysed. Employing the linear sloshing theorem, we construct an accurate numerical and analytical approximation of natural sloshing mode in rectangular container with perforated baffle. Two dimensional irrotational flow of an ideal incompressible liquid is assumed. Finally the dissipated energy is being measured and equal viscous damping was calculated. So the perforation in which the damping is being maximized is determined and finally the results being compared with some experimental and analytical results from journal paper
An efficient reduced-order modelling approach based on fluid eigenmodes and boundary element method
, Article Journal of Fluids and Structures ; Volume 23, Issue 1 , 2007 , Pages 143-153 ; 08899746 (ISSN) ; Nobari, A. S ; Behbahani Nejad, M ; Haddadpour, H ; Sharif University of Technology
2007
Abstract
This paper presents an efficient reduced-order modelling approach based on the boundary element method. In this approach, the eigenvalue problem of the unsteady flows is defined based on the unknown wake singularities. By constructing this reduced-order model, the body quasi-static eigenmodes are removed from the eigensystem and it is possible to obtain satisfactory results without using the static correction technique when enough eigenmodes are used. In addition to the conventional method, eigenanalysis and reduced-order modelling of unsteady flows over a NACA 0012 airfoil, a wing with NACA 0012 section and a wing-body combination are performed using the proposed reduced order modelling...
Influence of Shear Wall Positioning in Design of Concrete Frames
, M.Sc. Thesis Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
Numerous research is available in the literature regarding shear walls. These have considered parameters like wall cross-section, Reinforcement configuration, boundary elements, etc. In addition, seismic and wind loading behavior has been discussed. Currently, the software ETABS is used extensively in automatic design of shear walls, The programs design bases are investigated in this thesis in ragards to flexural, shear and boundary elements of shear walls under seismic loading. The attachment of wall elements to frame (column) elements is of particular interest in this study
A FEM-BEM Model for Investigation of Fuel SlushingEffect on the Supersonic Wing Aeroelasticity
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor)
Abstract
In the present work the stability analysis for the coupled aeroelasticity and fuel sloshing in supersonic wings is represented. The wing and store structure is modeled using the finite element method. The supersonic wing aerodynamic is modeled by the linear piston theory and store aerodynamic is modeled by the semi-stable slender body piston theory. Fuel sloshing in the store with desired geometry is modeled by the boundary element method. The coupled structure, aerodynamic and sloshing governing equations are drawn by using the Galerkin method and reduce order modeling teqnique for them and an effective numerical model was developed that is capable to analyze the stability for...
A Numerical Investigation on Ultimate Strength of Steel Plate Shear Walls Utilizing Various Boundary Frame Elements and Different In-fill Plate Thicknesses
, M.Sc. Thesis Sharif University of Technology ; Khalu, Alireza (Supervisor)
Abstract
In this thesis different steel plate shear walls have been investigated using ABAQUS software. These investigations have been focused on various topics, including both boundary frame elements and also the in-fill plate. The main results have been gathered by utilizing different steel plate thicknesses and different boundary frame elements. In order to achieve a better understanding of the effects of both of these elements, various aspect ratios have also been investigated. Moment of inertia has been noted as the main property of both beams and columns used in SPSW. Comparison of the gained results is noteworthy. They show a variety of changes in the load-displacement diagrams, due to changes...
Calculation of Heterogenous Material Properties by Using of Eshelby based and BEM Methods
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkheili, Ali (Supervisor)
Abstract
To days the heterogeneous material are used extensively in the engineering materials. Optimization ability is a key feature of these materials to reach desired properties. Heterogeneous materials are the materials that make up from the constituents of multiphase materials in lower length scale such as mesoscopic, microscopic or/and Nano scales. So the properties of these materials at each scale are depending on to several characteristics of heterogeneities such as geometry, material and packing. In these materials the effects of heterogeneities at the lower scales are very significant and the constitutive equations are different for each range of scale. The proper selection of this range...
Unsteady Hydrodynamic Simulation of Flexible Bodies using Boundary Element Method
, Ph.D. Dissertation Sharif University of Technology ; Abbaspour Tehrani, Majid (Supervisor)
Abstract
For more than a million years, aquatic animals and specially fishes make undulatory motions in their flexible body to propel themselves. In the recent decays, scientists prove that these mechanisms are more efficient than man-made propulsion systems. A wide variety of artificial vehicles including robotfishes, ROV and etc has been manufactured with inspiring by natural creatures. The Biomimetic science which deals with the study of mechanics and hydrodynamics of living creatures is very important in developing these vehicles. In the present study, numerical software (PANEL3D®), bases on boundary integral equations of potential flow have been developed to simulate hydrodynamic performance of...
Development of Neutron Noise Simulator Based on the Boundary Element Method
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Aboulfazl (Supervisor)
Abstract
The present M.Sc. thesis consists of two sections including static calculation and neutron noise calculations in rectangular and hexagonal geometries. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equation is based on Boundary Element Method (BEM). The result are benchmarked against the valid results for BIBLIS-2D and IAEA -2D benchmark problem. In the second section, neutron noise calculation are performed for two types of noise sources, i.e. absorber of variable strength and Inadvertent Loading and Operation of a Fuel Assembly in an Improper Position (ILOFAIP). The...