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1
Content available Flow-induced Vibrations of a Horizontal Elastic Band Plate Submerged in Fluid of Finite Depth
Szmidt Kazimierz, Hedzielski Benedykt
Archives of Hydro-Engineering and Environmental Mechanics
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2019
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Vol. 66, nr 3-4
101--130
EN
The paper deals with forced vibrations of a horizontal thin elastic plate submerged in a semi-infinite layer of fluid of constant depth. The pressure load on this plate is induced by water waves arriving at the plate. This load is accompanied by pressure resulting from the motion of the plate. The plate and fluid motions depend on boundary conditions, and, in particular, the pressure load depends on the width of the gap between the plate and the bottom. In theoretical description of the phenomenon, we deal with a coupled problem of hydrodynamics in which the plate and fluid motions are coupled through boundary conditions at the plate surfaces. The main attention is focused on transient solutions of the problem, which correspond to fluid (and plate) motion starting from rest. In formulation of this problem, a linear theory of small deflections of the plate is employed. In order to calculate the fluid pressure, a solution of Laplace’s equation is constructed in a doubly connected fluid domain. With respect to the initial value problem considered, we confine our attention to a finite fluid domain. For a finite elapse of time, measured from the starting point, the solution in the finite fluid area mimics a solution within an infinite domain, inherent for wave propagation problems. Because of the complicated structure of boundary conditions of the coupled problem considered, the fluid domain is divided into sub-domains of simple geometry, and the solutions of the problem equations are constructed separately in each of these domains. Numerical experiments have been conducted to illustrate the formulation developed in this paper.
2
Content available remote Numerical solution of electroheat problems with time-varying geometries
Doležel I., Kotlan V., Hamar R., Pánek D.
Przegląd Elektrotechniczny
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2018
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R. 94, nr 1
25--28
EN
Novel approach to modeling of 3D coupled electroheat problems with time-varying geometries is presented. Instead of time-expensive remeshing of the whole system in every time step it is used the initial mesh that takes into account the expected geometric changes. In the course of computations, its relevant elements are able to adaptively change their shapes and material parameters. The methodology is illustrated with an example of induction-assisted laser cladding.
PL
W artykule przedstawiono nowe podejście do trójwymiarowego modelowania problemów elektrotermicznych ze zmiennymi w czasie geometriami. Zamiast stosowania czaochłonnych metod remeshingu w każdym kroku czasowym wprowadzono początkową siatkę, biorącą pod uwagę oczekiwane zmiany geometryczne. W procesie obliczaniea istotne element siatki są w stanie sdaptacyjnie zmieniać ich kształt i paramatry materiałowe. Przedstawiona metodologia został zilustrowana przykładem wspomaganego indukcyjnie okładzinowania laserowego.
3
Content available Identification of temperature and hardness distribution during dual frequency induction hardening of gear wheels
Barglik J.
Archives of Electrical Engineering
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2018
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Vol. 67, nr 4
913--923
EN
Induction surface hardening means the hardening of a thin zone of the material only, while its core remains soft. The paper deals with the modelling of the Consecutive Dual Frequency Induction Hardening (CDFIH) of gear wheels and its validation. For gear wheels with modulus m smaller than 6 mm a contour profile of hardness distribution could be obtained. The investigated gear wheel is heated first by a medium frequency inductor to the temperature approximately equal to the modified lower temperature Ac1m. It means beginning of the austenite transformation. Then the gear wheel is heated by the high frequency inductor to the hardening temperature making it possible to complete the austenite transformation and immediately cooled. In order to design the process it is necessary to identify modified critical temperatures and to obtain expected temperature distribution within the whole tooth.
4
Content available remote Cogging force and frequency bandwidth of a vibration energy harvester with nonlinear electromechanical resonance
Jagieła M., Kulik M.
Przegląd Elektrotechniczny
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2017
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R. 93, nr 1
311--315
EN
The paper analyses the open-circuit frequency characteristics of a mechanical vibration energy harvester comprising of a single-coil cored armature and two vibrating yokes with permanent magnets connected to a plate spring. The cogging force, developed by action of the magnetic flux on the core brings a nonlinear component into system kinematics and causes complex variation of the frequency characteristics. It is shown that depending on dimensions of the generator parts, the system is capable of developing the frequency characteristics whose resonant frequency decreases or increases with the magnitude of external force. Through analysis supported by computer simulations using the finite element models it is shown that the systems with decreasing resonant frequency are more practical due to wider frequency bandwidth and higher amplitude of the generated voltage.
PL
W artykule analizowane są właściwości układu przetwarzania drgań mechanicznych w energię elektryczną zbudowanego z generatora liniowego z pojedynczą cewką z rdzeniem ferromagnetycznym oraz dwóch ruchomych jarzm z magnesami trwałymi połączonymi z metalową sprężyną paskową. Pokazano, że układ o takiej budowie może wytwarzać dwa rodzaje charakterystyk częstotliwościowych, tj. takie w których częstotliwość rezonansowa maleje lub rośnie wraz z amplitudą zewnętrznej siły wymuszającej drgania. Za pomocą symulacji komputerowych z wykorzystaniem modeli siatkowych, pokazano, że w układach praktycznych powinno dążyć się do osiągnięcia pierwszego typu charakterystyk ze względu na szersze pasmo częstotliwości oraz większą amplitudę generowanego napięcia.
5
Content available Model of magnetic gun with respecting eddy currents
Leubner K., Doležel I., Laga R.
Poznan University of Technology Academic Journals. Electrical Engineering
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2015
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No. 81
21--29
EN
A sophisticated mathematical model of the magnetic gun is presented and solved numerically. The model consists of three strongly non-linear and non-stationary differential equations describing the time-dependent distribution of magnetic field in the device, current in the field circuit and movement of the projectile. The numerical solution is carried out in the application Agros2D based on a fully adaptive higher-order finite element method. The results are processed in Wolfram Mathematica. The methodology is illustrated by an example and selected results are compared with experiment.
6
Content available Model of magnetic gun with respecting eddy currents
Leubner K., Doležel I., Laga R.
Computer Applications in Electrical Engineering
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2015
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Vol. 13
12--20
EN
A sophisticated mathematical model of the magnetic gun is presented and solved numerically. The model consists of three strongly non-linear and non-stationary differential equations describing the time-dependent distribution of magnetic field in the device, current in the field circuit and movement of the projectile. The numerical solution is carried out in the application Agros2D based on a fully adaptive higher-order finite element method. The results are processed in Wolfram Mathematica. The methodology is illustrated with an example and selected results are compared with experiment.
7
Content available remote Schur complement method with iterative solver for 2D fieldcircuit coupling finite element problem with movement
Marcsa D., Kuczmann M.
Przegląd Elektrotechniczny
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2014
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R. 90, nr 12
145--148
EN
The analysis and design of electromechanical devices involve the solution of large sparse linear systems, and require therefore high performance algorithms. In this paper, the Schur complement method with parallel preconditioned conjugate gradient (PCG) solver is introduced in two-dimensional parallel time-stepping finite element formulation to analyse rotating machine considering the electromagnetic field, external circuit and rotor movement. The proposed parallel solver is analysed concerning its computational efficiency and number of iterations. Simulation results of a rotating machine are also presented.
PL
Analiza i projektowanie urządzeń elektromechanicznych zawierają rozwiązanie dużych układów równań z macierzami rzadkimi, i dlatego wymagają algorytmów o wysokiej wydajności. W artykule metodę uzupełnień Schura z algorytmem opartym na metodzie gradientów sprzężonych wprowadzono do dwuwymiarowego, równoległego, czasowokrokowego sformułowania elementów skończonych do analizy maszyny elektrycznej od strony pola elektromagnetycznego, obwodu elektrycznego zewnętrznego oraz ruchu wirnika. Proponowany równoległy algorytm został poddany analizie pod kątem jego wydajności obliczeniowej, oraz liczby iteracji. Rezultaty symulacji maszyny wirującej są także przytoczone.
8
Content available remote Modeling of Induction Shrink Fit of Action Wheel in Gas Turbine
Doležel I., Kotlan V., Ulrych B.
Przegląd Elektrotechniczny
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2012
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R. 88, nr 1a
151-154
EN
Induction shrink fit in a gas turbine is modeled. The fit is realized by pressing of a heated steel wheel carrying the blades on shaft and its purpose is to transfer a relatively high torque in specific operation conditions. The paper deals with the numerical solution of the process that represents a nonlinear and nonstationary coupled problem characterized by interaction of magnetic field, temperature field and field of thermoelastic displacements. The methodology is illustrated by a typical example whose results are discussed.
PL
Zaproponowano modelowanie indukcyjnego dopasowania koła w turbinie gazowej. Dopasowanie to polega na naprężaniu rozgrzanego koła w celu ułatwienia transferu dużego momentu. Przedstawiono model numeryczny procesu uwzględniający pola magnetyczne i temperaturpowe oraz odkształcenie termoelastyczne.
9
Content available remote Numerical modelling of a multi-physical problem within an encapsulated three-phase transformer and its surroundings
Smolka J., Nowak A. J., Ingham D.B., Elliot L.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2006
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Vol. 10, No 1
63-81
EN
The paper presents a numerical thermal model of an encapsulated three-phase electrical transformer. The model is based on the multi-physical approach and involves heat transfer analysis coupled with the examination of specific power losses in the coils and the core using electromagnetic field analysis as well as determination of thermal stresses. The thermal boundary conditions (i. e. local heat fluxes) are determined by considering a numerical model of the surrounding air. Additionally, the device is cooled via radiation (from the external walls) and forced convection (a water cooling system). A few different configurations of the cooler and the heat pipes are also analyzed. Moreover, anisotropic material properties were applied for stranded coils and the core. A partial experimental validation of the model has shown that the temperature distribution within the transformer is more realistic and closer to the measurements when compared with the previous analysis limited to heat transfer problems only with uniform internal heat sources and isotropic material properties. The total heat transfer rate indicates that forced convection is the most important heat dissipation mechanism in this model. The significance of the water cooling system has also been established in calculations of crack presence in the model.
10
Fundamentals of direct methods in poroplasticity
Maier G., Cocchetti G.
Foundations of Civil and Environmental Engineering
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2002
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No. 1
11-136
EN
A nonlinear initial-boundary-value coupled problem, central to poroplasticity, is formulated under the hypotheses of small deformations, quasi-static regime, full saturation, linear Darcy diffusion law and piecewise-linearized stable and hardening poroplastic material model. After a preliminary nonconventional multifield (mixed) finite element modelling, shakedown and upper bound theorems are presented and discussed, numeri-cally tested and applied to dam engineering situations using commercial linear and quadratic programming solvers. Limitations of the presented methodology and future prospects are discussed in the conclusions.
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