Wyniki wyszukiwania - BazTech

1

Application of the boundary element method in 3D models of grounding systems

Mączka Mariusz, Pawłowski Stanisław, Plewako Jolanta, Sikora Roman, Markiewicz Przemysław

Przegląd Elektrotechniczny

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2025

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R. 101, nr 1

195--198

EN

The paper describes a numerical model of a grounding system enabling simulations of stationary fields in three-dimensional geometries. The developed model is based on the Boundary Element Method using the potential density function of a single layer, which makes it efficient and accurate. The results of simulations of potential distributions, electric field, and calculations of basic grounding parameters such as step voltage or ground resistance for a typical system application are presented.

PL

W artykule opisano model numeryczny układu uziemiającego umożliwiający symulację pól stacjonarnych w geometrii trójwymiarowej. Opracowany model opiera się na Metodzie Elementów Brzegowych wykorzystując funkcję gęstości potencjału pojedynczej warstwy, co czyni go wydajnym i dokładnym. W artykule przedstawiono wyniki symulacji rozkładów potencjałów, pola elektrycznego oraz obliczeń podstawowych parametrów uziemienia, takich jak napięcie krokowe czy rezystancja uziemienia, dla typowego zastosowania systemu.

2

Modeling of photochemical and photothermal effects in soft tissue subjected to laser irradiation

Jasiński Marek, Zadoń Maria

Computer Assisted Methods in Engineering and Science

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2024

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Vol. 31, no. 1

29--50

EN

The purpose of this study is to analyze the phenomena that occur in biological tissueduring photodynamic therapy (PDT). Under the influence of the laser, triplet oxygen istransformed into singlet oxygen, which is cytotoxic to cancer tissue. The impact of thelaser on the tissue may also be accompanied by changes in the thermophysical parameters,e.g., perfusion, which can affect the supply of oxygen to the tissue and, consequently,the outcome of the therapy. The proposed model uses the optical diffusion equation,the Pennes bioheat transfer equation, and reactions equations for PDT. The connectionbetween bioheat transfer and PDT models is taken into account through the respectiverelationships between perfusion rate, capillary blood velocity, and the maximum oxygensupply rate. Furthermore, a method is proposed to model abnormal vascular patterns inthe tumor subdomain. The boundary element method and the finite difference methodwere used in the numerical implementation stage.

3

Identification of an Arbitrary Shape Obstacle of Scattering Problem Using Near Field Data

Rymarczyk Tomasz, Sikora Jan, Kulisz Monika, Kłosowski Grzegorz

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no. 7

396--405

EN

This paper delves into a significant area of research, exploring the application of the standard boundary element method (BEM) to analyze inverse acoustic frequency scattering problems in 2D space using a rigid corrugated circular object. The inverse problem is reformulated as an optimization problem, with the boundary of the scatterer parametrized to reduce the number of optimization variables. The influence of these parameters on imaging results based on near-field data is examined. The analysis uses a flat wave illuminating the object along the positive x-axis direction. The study evaluates the accuracy of the solution across various parameters defining the boundary of the analyzed object. The findings, which significantly contribute to advancements in computational methods, non-destructive testing, and the understanding of functional properties of materials and structures, offer valuable insights into numerical techniques and their practical engineering applications.

4

Modelling of the acoustic wave scattering on the aircraft surface using the boundary element method

Nowicki Dawid, Suder-Dębska Katarzyna, Czajka Ireneusz

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023107

EN

Sound localization tools are important in the environmental protection and the human searches. The article is one of the stages of the implementation of the concept of using aircraft to localize sound sources. The use of a fixed-wing aircraft instead of a multirotor would increase the total flight time, and expand the surveyed area. It is important to determine the most favourable positions of the receivers on the surface of the aircraft. The scattering effects of the sound waves coming from the ground source and aircraft engine on the acoustic field on the aircraft surface are not homogeneous. In the article the authors present the modelling of the scattering of the sound waves over the airplane surface with the usage of boundary element methods. After determining the effects from the sound source on earth and from the aircraft engine the conclusion was made, that the influence from the engine noise is greater than that from the ground source, and in order to localize the low amplitude signals, the aircraft need to glide. Considering only the effects of the ground source, the optimal areas for the microphones placement were determined.

5

Scattering problems in 2D space within the Rayleigh regime

Sikora Jan

Przegląd Elektrotechniczny

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2023

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R. 99, nr 2

173--177

EN

In this paper, the application of the classic method of boundary elements to analyse the scattering problems of acoustic waves by a rigid object with a circular cross-section in 2D space is presented. The analysis is presented on the example of a flat wave falling on an object along the x-axis positive direction. The accuracy of the solution for two different cases meeting the Rayleigh regime was analysed. The criteria that must be met in order to expect a reliable solution are provided.

PL

W pracy przedstawiono zastosowanie klasycznej metody elementów brzegowych do analizy problemów rozpraszania fal akustycznych przez sztywny obiekt o przekroju kołowym w przestrzeni 2D. Analizę przedstawiono na przykładzie fali płaskiej padającej na obiekt zgodny z dodatnim kierunkiem osi x. Przeanalizowano dokładność rozwiązania dla dwóch różnych przypadków spełniających wymagania reżimu Rayleigh’a. Podano kryteria jakie muszą być spełnione, aby można było oczekiwać wiarygodnego rozwiązania.

6

Sensitivity to Gauss quadrature of isogeometric boundary element method for 2D potential problems

Alia Ahlem, Ben Said Hasna

Journal of Theoretical and Applied Mechanics

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2023

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Vol. 61 nr 3

585--597

EN

IsoGeometric Analysis (IGA) is widely used because it links exact geometry to analysis. When IGA is applied within the Boundary Element framework (IGBEM), and under cer- tain boundary conditions, discretization errors can be suppressed leading to an accurate estimation of the integration errors. By using the IGBEM for potential problems, the ef- fect of Gauss quadrature on the accuracy of each term arising in the IGBEM is studied for smooth geometry under constant boundary conditions. The results show that the method of computing singular integrals in the IGBEM is efficient. Results can be improved by selecting optimal numbers of Gauss points for both integrals.

7

Applications of the second-order edge element method versus zero order in optical diffusion tomography

Rymarczyk Tomasz, Sikora Jan

Przegląd Elektrotechniczny

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2022

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R. 98, nr 1

107--110

EN

This paper presents an approximation of two boundary elements by analysing numerical aspects of such an approximation. Diffusion optical tomography with defined region geometry was used for this purpose. The Helmholtz equation in the frequency domain was transformed to integral form. The inverse problem was defined as an optimal shape design problem. The conversion of the imaging problem to an inverse task required the solution of the PDE by the BEM. Remesh in the optimisation process is not required in contrast to the solution of the MES. Two different approximations are compared, and the results of the research work are presented. The proposed method depends on the configuration of the object or objects within the region and the starting position and dimensions of the circular inclusion.

PL

W artykule przedstawiono aproksymację dwóch elementów brzegowych analizując numerycznych aspekty takiego przybliżenia. Wykorzystano do tego dyfuzyjną tomografię optyczną z określoną geometrią regionu. Równanie Helmholtza w dziedzinie częstotliwości przekształcono do postaci całkowej. Problem odwrotny został zdefiniowany jako problem projektowania optymalnego kształtu. Konwersja problemu obrazowania na zadanie odwrotne wymagała rozwiązania PDE przez BEM. Remesh w procesie optymalizacji nie jest wymagany w przeciwieństwie do rozwiązania MES. Porównano dwa różne przybliżenia. Proponowana metoda silnie zależy od konfiguracji obiektu lub obiektów wewnątrz regionu oraz pozycji wyjściowej i wymiarów wtrącenia kołowego.

8

Strength analysis of sandwich beams with linear elastic inner layer

Kimura Koichi

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 3

31--44

EN

A waterproof or water-resistant sandwich structure which consists of housing chassis and a gasket requires that gasket contact pressure, which depends on bolt axial force, is greater than the design minimum pressure on the entire circumference. However, it is also necessary that gasket contact pressure is smaller than the maximum permissible gasket pressure. If the maximum stress in chassis can be calculated from bolt axial force, gasket specifications and chassis stiffness, it is helpful for a design of such waterproof structures. In this study, chassis have been regarded as Bernoulli-Euler beams, and two simple numerical methods have thus been derived. Numerical results using the proposed method are sufficiently converged even in case that the number of partitions is about 10.

9

Numerical analysis of thermal damage and oxygen distribution in laser irradiated tissue

Jasiński Marek

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 2

51--62

EN

A numerical analysis of the thermal damage process that proceeds in biological tissue during laser irradiation is presented. Heat transfer in the tissue is assumed to be transient and two-dimensional. The internal heat source resulting from the laser irradiation based on the solution of optical diffusion equation is taken into account. Changes in tissue oxygen distribution resulting from temperature changes are analyzed using the Krogh cylinder model with Michaelis-Menten kinetics. A Hill model was used to describe the oxyhemoglobin dissociation curve. At the stage of numerical realization, the boundary element method and the finite difference method have been applied.

10

Mathematical modeling of the phenomena that occur in a biological tissue containing photosensitizer

Jasiński Marek, Zadoń Maria

Journal of Applied Mathematics and Computational Mechanics

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2022

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Vol. 21, nr 4

40--51

EN

The aim of the study is to analyze photothermal and photochemical phenomena that occur during photodynamic therapy (PDT). In this type of therapy, under the influence of the laser, reactions take place related to the transformation of triplet oxygen form into its singlet form which is cytotoxic to the tissue. The increases in temperature resulting from the laser-tissue interaction during PDT are not big; however, they can lead to changes in tissue perfusion, which can affect oxygen delivery to the tissue. The proposed model uses optical diffusion equation, Pennes bioheat transfer equation, and reactions equations for PDT. The main findings of the analysis show the impact of temperature on the value of the perfusion coefficient and triplet oxygen distributions at the end of the treatment procedure.

11

Taking account of the shift and inertia of rotation in problems of diagnostics of the spectra of critical forces mechanical systems

Orobey Viktor, Nemchuk Oleksii, Lymarenko Oleksandr, Piterska Varvara, Lohinova Liliia

Diagnostyka

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2021

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Vol. 22, No. 1

39--44

EN

Diagnostics of stability of the cores constructions, elements of the carrier system of the ship and port facilities, reduces to the definition of critical forces, excess which causes a transition of the system from one equilibrium state to another. Such a transition often leads to the destruction of the constructions or other forms of accidents, and therefore it is extremely undesirable and for practice it is important to knowledge of a specific spectrum of critical forces and their corresponding forms of loss of stability.

12

A meshless method for subsonic stall flutter analysis of turbomachinery 3D blade cascade

Prasad Chandra Shekhar, Šnábl Pavel, Pešek Luděk

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 6

art. no. e139000

EN

The analysis of subsonic stall flutter in turbomachinery blade cascade is carried out using a medium-fidelity reduced-order aeroelastic numerical model. The model is a type of field mesh-free approach and based on a hybrid boundary element method. The medium-fidelity flow solver is developed on the principle of viscous-inviscid two-way weak-coupling approach. The hybrid flow solver is employed to model separated flow and stall flutter in the 3D blade cascade at subsonic speed. The aerodynamic damping coefficient w.r.t. inter blade phase angle in traveling-wave mode is estimated along with other parameters. The same stability parameter is used to analyze the cascade flutter resistance regime. The estimated results are validated against experimental measurements as well as Navier-Stokes based high fidelity CFD model. The simulated results show good agreement with experimental data. Furthermore, the hybrid flow solver has managed to bring down the computational cost significantly as compared to mesh-based CFD models. Therefore, all the prime objectives of the research have been successfully achieved.

13

Transient dynamic analysis of functionally graded micro-beams considering small-scale effects

Eshraghi I., Dag S.

Archives of Mechanics

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2021

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Vol. 73, nr 4

303--337

EN

A domain-boundary element method, based on modified couple stress theory, is developed for transient dynamic analysis of functionally graded micro-beams. Incorporating static fundamental solutions as weight functions in weighted residual expressions, governing partial differential equations of motion are converted to a set of coupled integral equations. A system of ordinary differential equations in time is obtained by domain discretization and solved using the Houbolt time marching scheme. Developed procedures are verified through comparisons to the results available in the literature for micro- and macro-scale beams. Numerical results illustrate elastodynamic responses of graded micro-beams subjected to various loading types. It is shown that metal-rich micro-beams and those with a smaller length scale parameter ratio undergo higher displacements and are subjected to larger normal stresses.

14

Acoustic Attenuation Performance Analysis and Optimisation of Expansion Chamber Coupled Micro-perforated Cylindrical Panel Using Response Surface Method

Alisah Mohamad Izudin, Ooi Lu Ean, Ripin Zaidi Mohd, Yahaya Ahmad Fadzli, Ho Kelvin

Archives of Acoustics

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2021

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Vol. 46, No. 3

507--517

EN

This paper describes the boundary element method (BEM) and the experimental and optimisation studies conducted to understand the potential of expansion chamber coupled micro-perforated cylindrical panel (MPCP) in enhancing the acoustic attenuation for in-duct noise control issues. Owing to the complex structure of the MPCP and to achieve the correct prediction of acoustic attenuation, BEM is adopted on the basis of the Simcenter 3D software to compute the sound transmission loss (TL), As the MPCP is cylindrical in shape with numbers of sub-milimeter holes, additive manufacturing-based 3D printing is utilised for the model prototyping to reduce current design limitation and enable fast fabrication. The TL measurement-based two-load method is adopted for model validation. Subsequently, parametric studies of the MPCP concerning the perforation hole diameter, perforation ratio and depth of air space are carried out to investigate the acoustic performance. Optimisation via response surface method is used as it allows for evaluating the effects of multiple parameters as required in this study. The model validation result shows that the error between the BEM and the measured values is relatively small and shows good agreement. The R-square value is 0.89. The finding from the parametric studies shows that a wider peak attenuation can be achieved by reducing the perforation hole diameter, and one way to increase the TL amplitude is by increasing the air cavity depth. Finally, the optimised MPCP model is adopted to the commercial vacuum cleaner for verification. The sound pressure level of the vacuum cleaner is significantly attenuated within the objective frequency of 1.7 kHz.

15

Gas flow simulation in the working gap of impulse gas-barrier face seal

Kuznetsov Eduard, Nahornyi Volodymyr, Krenický Tibor

Management Systems in Production Engineering

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2020

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nr 4 (28)

298--303

EN

Numerical simulation method of the working process of a centrifugal unit contactless face impulse seal is proposed. A seal functioning physical model was created. Its operation key aspects that are not taken into account in the traditional methods of calculating contactless impulse seals are identified. A numerical simulation of seal working process based on the Reynolds equation solution for the medium vortex-free motion in the gap between moving surfaces is proposed. Hypothesis that simplify the equation's numerical solution for the face impulse seal is formulated. The numerical solution is obtained using the boundary element method. Based on the obtained numerical solution, the distribution of the working medium pressure field in the seal gap is simulated.

16

Potential-based boundary element method to calculate the hydrodynamic drift force on the floating cylinder

Ghafari Hamidreza, Motallebi Mohammad, Ghassemi Hassan

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 4

69--79

EN

This paper presents the calculation of the hydrodynamic drift force by using the potetial-based boundary element method (BEM). The potential theory and far-field wave drift forces solution will be described. The comparison of non-dimensional drift force for surge and heave motions are in good agreement between numerical and experimental data. The effect of different drafts and the radius of a cylinder on the drift forces (surge, heave and pitch) are presented and discussed.

17

Homogenization of plates with parallel cracks

Holek Mateusz, Fedeliński Piotr

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 1

31--41

EN

The paper presents an analysis of effective elastic properties of plates with parallel cracks using the finite element method (FEM) and the boundary element method (BEM). Rectangular plates with parallel or inclined cracks to the edges of plates were considered. Different distances between cracks and different angles of cracks were studied. The displacement and traction boundary conditions were applied and their influence on the accuracy of overall properties of cracked material was analysed. The results obtained by the FEM and the BEM were compared.

18

Liquid vibrations in cylindrical tanks with and without baffles under lateral and longitudinal excitations

Strelnikova E., Kriutchenko D., Gnitko V., Tonkonozhenko A.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 3

117--132

EN

The paper is devoted to issues of estimating free surface elevations in rigid cylindrical fluid-filled tanks dunder external loadings. The possibility of baffles installation is provided. The liquid vibrations caused by lateral and longitudinal harmonic loadings are under consideration. Free, forced and parametrical vibrations are examined. Modes of the free liquid vibrations are considered as basic functions for the analysis of forced and parametric vibrations. The modes of the free liquid vibrations in baffled and un-baffled cylindrical tanks are received by using single-domain and multi-domain boundary element methods. Effects of baffle installation are studied. The problems of forced vibrations are reduced to solving the systems of second order ordinary differential equations. For parametric vibrations the system of Mathieu equations is obtained. The numerical simulation of free surface elevations at different loadings and baffle configurations is accomplished. Beat phenomena effects are considered under lateral harmonic excitations. The phenomenon of parametric resonance is examined under longitudinal harmonic excitations.

19

Application of 1-D and 2-D discrete wavelet transform to crack identification in statically and dynamically loaded plates

Knitter-Piatkowska Anna, Guminiak Michał

Engineering Transactions

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2020

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Vol. 68, iss. 2

137--157

EN

The paper presents the problem of damage detection in thin plates while considering the influence of static and dynamic characteristics, especially with regard to the modes of vibration as well as the excitation by static loads. The problem of Kirchhoff plate bending is described and solved by the Boundary Element Method (BEM). Rectangular plates supported on boundary or plates supported on boundary and resting on the internal columns are examined. A defect is introduced by the additional edges forming a crack in the plate domain. The analyses of static and dynamic structural responses are carried out with the use of Discrete Wavelet Transform (DWT). Signal decomposition according to the Mallat pyramid algorithm is applied. To obtain a more adequate input function subjected to DWT the white noise disturbing the signal is considered together with the structural response. In the dynamic experiments the plate undergoes vibrations similar to natural modes. The measured variables are static deflections and vertical displacement amplitudes. All of them are established at internal collocation points distributed alongside the line parallel to selected plate edge.

20

Finite and boundary element analysis of crack closure

Holek Mateusz, Fedeliński Piotr

Computer Methods in Materials Science

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2020

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Vol. 20, No. 1

7--13

EN

The aim of this work is an analysis of contact pressure between crack surfaces and its influence on effective elastic properties of materials with randomly distributed cracks. The finite element method (FEM) and the boundary element methods (BEM) are applied to the numerical analysis of materials, and the results are compared. Three numerical results are presented. The accuracy of contact pressure obtained by numerical solutions is verified for a single inclined crack in an infinite plate subjected to compression by comparison with an analytical solution. The influence of angle between cracks and directions of compressive loading on contact pressure for a branched crack in a rectangular plate is studied. The effective Young moduli and Poisson ratios for a rectangular plate with randomly distributed cracks are computed. The plate contains intersecting cracks which are in contact when the plate is subjected to tension or compression.

PL

Celem pracy jest analiza sił kontaktowych między powierzchniami pęknięć i ich wpływu na zastępcze własności sprężyste materiałów z losowo rozmieszczonymi pęknięciami. Zastosowano metodę elementów skończonych (MES) i metodę elementów brzegowych (MEB) w analizie numerycznej materiałów i porównano wyniki obliczeń. Przedstawiono trzy przykłady numeryczne. Zbadano dokładność sił kontaktowych wyznaczonych metodami numerycznymi przez porównanie z rozwiązaniem analitycznym dla pojedynczego ukośnego pęknięcia w ściskanej nieskończonej tarczy. Badano wpływ kąta między pęknięciami i kierunków obciążenia ściskającego na siły kontaktowe rozgałęzionego pęknięcia w tarczy prostokątnej. Obliczono zastępcze moduły Younga i współczynniki Poissona prostokątnej tarczy z losowo rozmieszczonymi pęknięciami. Tarcza zawierała przecinające się pęknięcia, które stykają się, gdy tarcza jest rozciągana lub ściskana.