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    Wyświetlanie 1-14 z 14
    Tytuł:
    Instability of the non-isothermal flow between a rotating and a stationary disks
    Autorzy:
    Tuliszka-Sznitko, E.
    Soong, C. Y.
    Serre, E.
    Bontoux, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1967641.pdf
    Data publikacji:
    2001
    Wydawca:
    Politechnika Gdańska
    Tematy:
    rotational flow
    stationary disks
    flow instability
    transition flow
    convective/absolute transition
    Opis:
    Both theoretical linear stability analysis and direct numerical simulation are performed to study the transition flow between rotating discs. The paper reports three-dimensional spiral and annular patterns computed with a high-order (spectral) numerical method in the Bodewadt layer of a cylindrical rotor/stator cavity. The characteristic parameters of these boundary layer instabilities are compared with the theoretical results and interpreted in terms of type I and type II generic instabilities. The absolute instability regions are theoretically identified and critical Reynolds numbers of the convective/absolute transition in both layers are given. The absolute or convective nature of the flows is determined by examining the branch-point singularities of the dispersion relation.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2001, 5, 4; 557-566
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Band structure of ruthenate superconductors
    Autorzy:
    Dow, J.
    Zolotovsky, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1934032.pdf
    Data publikacji:
    2011
    Wydawca:
    Politechnika Gdańska
    Tematy:
    band structure
    superconductors
    transition temperature
    Opis:
    We investigate the band structure of ruthenates using the first-principles method of density functional theory (DFT). We calculated the band structure and density of states at the Fermi level for superconductors Ba2YRuO6 and Sr2YRuO6. Our calculations show that the maximum critical superconducting transition temperature Tc=93K can be obtained for Ba2YRuO6.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 1; 99-105
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of limiting walls on shock wave structure in single passage test section with compressor profile
    Autorzy:
    Piotrowicz, M.
    Flaszyński, P.
    Szwaba, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1938636.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Gdańska
    Tematy:
    shock wave
    laminar-turbulent transition
    transonic compressor
    Opis:
    The shock wave boundary layer interaction on the suction side of a transonic compressor blade is one of the main objectives of the TFAST project (Transition Location Effect on Shock Wave Boundary Layer Interaction). In order to look more closely into the flow structure on the suction side of the blade, a design of a turbine passage model in a rectilinear transonic wind tunnel was proposed. The model which could reproduce the flow structure, the shock wave location, the pressure distribution and the boundary layer development similar to the obtained in a reference cascade profile is the main objective of the design presented here. The design of the proposed test section is very challenging, because of the existence of a shock wave, its interaction with the boundary layer and its influence on the 3-D flow structure in the test section. The paper presents the influence of the test section geometry configuration on the flow structure as an effect of the shock wave boundary layer interaction.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2015, 19, 2; 141-152
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of artificial neural networks (ANN) as multiple degradation classifiers in thermal and flow diagnostics
    Autorzy:
    Głuch, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1964167.pdf
    Data publikacji:
    2005
    Wydawca:
    Politechnika Gdańska
    Tematy:
    rotating cavity
    direct method
    laminar-turbulent transition
    Opis:
    Application of a neural network of the classifier type for diagnostic purposes is presented. The described ANN solves the task of recognizing causes of degradation of power units' thermal cycle components. Verification of the applied ANN responses is based on the presented research in the numerical simulation of selected power installations. The obtained results stand for a diagnosis worked out under condition of power cycle proper measurements. Considerably good obtained results prove that the ANN technique can be applied as an automatic detector of operational faults. Thus an ANN can serve as a support tool for operational decisions. The present work also offers a way of reducing training time.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2005, 9, 2; 199-210
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical investigation of instability of an annular rotating cavity
    Autorzy:
    Tuliszka-Sznitko, E.
    Zieliński, A.
    Polus, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1965152.pdf
    Data publikacji:
    2005
    Wydawca:
    Politechnika Gdańska
    Tematy:
    rotating cavity
    direct method
    laminar-turbulent transition
    Opis:
    A direct two-dimensional numerical simulation has been performed to study the transition flow in an annual rotating cavity. The spectral collocation method based on the Chebyshev polynomial is used to solve the incompressible Navier-Stokes equation. The time scheme is semi-implicit and second-order accurate; it corresponds to a combination of the second-order backward differentiation formula for the viscous diffusion term and the Adams-Bashforth scheme for the non-linear terms. The method uses a projection scheme to maintain the incompressibility constrain. The numerical computations, performed for an annular cavity of the aspect ratio L=2 and 5 and for the curvature parameters Rm=(R1+R0)/(R1-R0)=5, exhibit instability structures in the form of circular rolls. These structures are in good agreement with the other investigations, both experimental and theoretical.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2005, 9, 1; 5-15
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling of rough wall boundary layers with an intermittency transport model
    Autorzy:
    Elsner, W.
    Warzecha, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1943210.pdf
    Data publikacji:
    2010
    Wydawca:
    Politechnika Gdańska
    Tematy:
    surface roughness
    boundary layer
    turbulence
    transition modeling
    Opis:
    The paper presents a new extension of the -Ret model to account for both the laminar-turbulent transition and the surface roughness. The new modeling approach takes into account the pressure gradient, turbulence intensity and roughness height and density. In the transition region both the intermittency transport equation and the momentum thickness Reynolds number Ret transport equation, supplemented by the correlation of Stripf et al. (2009) suitable for rough wall boundary layers are used. An additional modification of the SST turbulence model allows for modeling a full turbulent boundary layer over surfaces with sand roughness. A comprehensive validation of the new method using transitional and fully turbulent test cases was performed. Flat plate data with a zero and non-zero pressure gradient test case as well as a high pressure turbine blade case were used for this purpose The studies proved that the new modeling approach appeared to be sufficiently precise and enabled a qualitative prediction of the boundary layer development for the tested flow configurations.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2010, 14, 3; 271-282
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Molecular dynamics study of temperature-induced structural changes in YBa2Cu3O7 crystal
    Autorzy:
    Bośko, J.
    Sadowski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/1954521.pdf
    Data publikacji:
    1999
    Wydawca:
    Politechnika Gdańska
    Tematy:
    MD simulations
    structure
    phase transition
    oxygen diffusion
    trajectory
    Opis:
    The structure of YBa2Cu3O7 crystal has been studied with the aid of molecular-dynamics (MD) technique. A two-body model potentials proposed by Zhang and Catlow have been used in MD simulations performed in wide range of temperature. The temperature-induced orthorhombic-to-tetragonal phase transition is observed. The distruction of the arrangement of atoms in the CuO chains due to diffusion of oxygen atoms is observed. The diffusion coefficients are calculated, and their variation as a function of temperature is analysed. The activation energy is estimated.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1999, 3, 3; 293-302
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Curie temperatures for the Ising model on Archimedean lattices
    Autorzy:
    Malarz, K.
    Zborek, M.
    Wróbel, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1964143.pdf
    Data publikacji:
    2005
    Wydawca:
    Politechnika Gdańska
    Tematy:
    computer modelling and simulation
    Ising model
    phase transition
    critical parameter
    Opis:
    Critical temperatures for the ferro-paramagnetic transition in the Ising model are evaluated for five Archimedean lattices, basing on Monte Carlo simulations. The obtained Curie temperatures are 1.25, 1.40, 1.45, 2.15 and 2.80 [J/kB] for (3,12 do2), (4,6,12), (4,8 do 2), (3,4,6,4) and (3 do 4,6) lattices, respectively.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2005, 9, 4; 475-480
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modelling of influence of turbulent transition on heat transfer conditions
    Autorzy:
    Bochon, K.
    Wróblewski, W.
    Dykas, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1943251.pdf
    Data publikacji:
    2008
    Wydawca:
    Politechnika Gdańska
    Tematy:
    laminar-turbulent transition
    Conjugate Heat Transfer (CHT)
    computational fluid dynamics CFD
    Opis:
    This article deals with the turbulent transition phenomenon modelling and its influence on heat transfer. The purpose of the analyses was to verify the transition modelling implemented in the ANSYS CFX 11 commercial code for popular test cases (low flow speed) described in literature, and then use it for verification of the in-house CFD code (created for compressible flows). The inhouse CFD code has been extended lately for the Conjugate Heat Transfer modelling (CHT) as well, taking into account important flow effects, especially the turbulent transition. A Wilcox k-omega turbulence model with the Low-Reynolds modification was used in the in-house code. The calculations in ANSYS CFX were made using an SST turbulence model and a gamma-theta transition model. A fully turbulent flow was modelled by means of both codes, and the results were compared with the available experimental data. Then, the turbulent transition for several test cases was analysed with ANSYS CFX. Afterwards, the in-house CFD code was verified by means of ANSYS CFX for a higher flow speed (Mach numbers). The CHT modelling was analysed by means of both codes and the results were compared and discussed. The conducted analyses show that the results obtained by means of both codes are comparable, but the turbulence model used in the in-house CFD code is simpler and requires less computation time. A modification of two equations turbulence models can be an alternative for design problems in more developed laminar/turbulent flows.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2008, 12, 3-4; 173-184
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The electronic properties of new Fe-based superconductors
    Autorzy:
    Kruchinin, S.
    Antonchenko, V.
    Zolotovsky, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1934012.pdf
    Data publikacji:
    2011
    Wydawca:
    Politechnika Gdańska
    Tematy:
    Fe-based superconductors
    band structure
    density of states
    critical superconducting transition temperature
    Opis:
    We investigate the band structure of Fe-based superconductors using the first-principle method of density-functional theory. We calculated the band structure and the density of states at the Fermi level for ReFeAsO (Re = Sm, Dy, Ho, Er) superconductors. Our calculations indicate that the maximum critical superconducting transition temperature Tc will be observed for compounds with Sm and Er. We predict that Tc=60K for ErFeAsO.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 2; 203-208
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A CFD package for the 3D Navier-Stokes computation of unsteady flows in turbomachines
    Autorzy:
    Thermann, H.
    Schmidt, S.
    Weiss, C.
    Niehuis, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1967647.pdf
    Data publikacji:
    2001
    Wydawca:
    Politechnika Gdańska
    Tematy:
    CFD
    computational fluid dynamics CFD
    turbomachinery
    laminar-to-turbulent transition
    flutter
    clocking
    Navier-Stokes package
    Opis:
    A 3D Navier-Stokes package for the time-accurate computation of unsteady flows in turbomachines with emphasis on wide applicability, portability and efficiency is presented. The package consists of three components: the elliptic grid generator FRAME, the parallelised implicit Reynolds- and Favre-averaged Navier-Stokes solver PANTA and the post-processor TREAT especially designed for unsteady flow phenomena. The applicability of the package covers both rotor/stator interaction and blade flutter phenomena in multirow and multipassage 2D, Quasi3D and general 3D configurations in a wide range of flow velocities (subsonic, transonic). For turbulent computations either a Low-Reynolds-Number k-" or k-! turbulence model is available. Additionally, an algebraic transition model can be chosen from a variety of different models to enhance the accuracy of prediction for transitional flow phenomena. A description of the underlying algorithms and numerical methods as well as the main features and characteristics of each of the three components is given. Furthermore, selected examples of typical turbomachinery applications are shown to demonstrate these features.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2001, 5, 4; 537-547
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical simulation of 3D flow in VKI-Genoa turbine cascade including laminar-turbulent transition
    Autorzy:
    Yerschov, S.
    Derevyanko, A.
    Yakovlev, V.
    Gryzun, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1938601.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Gdańska
    Tematy:
    numerical simulation
    3D flow
    turbine cascade
    laminar-turbulent transition
    turbulence kinetic energy
    secondary flows
    losses
    Opis:
    This study presents a numerical simulation of a 3D viscous flow in the VKI-Genoa cascade taking into account the laminar-turbulent transition. The numerical simulation is performed using the Reynolds-averaged Navier-Stokes equations and the two-equation k-ω SST turbulence model. The algebraic Production Term Modification model is used for modeling the laminar-turbulent transition. Computations of both fully turbulent and transitional flows are carried out. The Mach number contours, the turbulence kinetic energy, the entropy function as well as the limiting streamlines are presented. Our numerical results demonstrate the influence of the laminar-turbulent transition on the secondary flow pattern. The comparison between the present computational results and the existing experimental and numerical data shows that the proposed approach reflects sufficiently the physics of the laminar-turbulent transition in turbine cascades.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2016, 20, 1; 43-61
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Elastic properties of the rectangular crystalline phase of planar hard cyclic pentamers
    Autorzy:
    Tretiakov, K. V.
    Wojciechowski, K. W.
    Powiązania:
    https://bibliotekanauki.pl/articles/1965832.pdf
    Data publikacji:
    2001
    Wydawca:
    Politechnika Gdańska
    Tematy:
    elastic constants
    Poisson ratio
    hard molecule
    anisotropic body
    Monte Carlo simulations
    computer simulation
    close packing
    orientational phase transition
    Opis:
    Structural and elastic properties of the densest known solid phase of two-dimensional (2D) system of hard cyclic pentamers (each pentamer is composed of five discs which centres are placed at vertices of a perfect pentagon of sides equal to the disc diameter, delta) are studied by Monte Carlo simulations. The present study confirms that at high densities the pentamers form a 2D solid structure of rectangular lattice with two pentamers (which librate, without rotation, around their mean orientations) in the unit cell. Elastic constants calculated for this structure show that, in contrast to densely packed 2D hard cyclic heptamers (composed of seven discs of centres forming a perfect heptagon of sides equal to the disc diameter delta), the pentamers do not exhibit anomalous Poisson's ratios.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2001, 5, 3; 331-340
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Polar head charge of membrane modifiers and their biological activity: the Monte Carlo simulation studies
    Autorzy:
    Kubica, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/1953950.pdf
    Data publikacji:
    1998
    Wydawca:
    Politechnika Gdańska
    Tematy:
    Monte Carlo simulations
    membrane modifiers
    phospholipids
    Pink model
    membrane
    membrane simulations
    gel fluid transition
    polar head charge
    biological activity
    Opis:
    On the basis of the 10-state Pink model, the effect of the polar head charge of amphiphilic modifier molecules has been discussed. It was shown, that for small concentrations of anionic and cationic compounds inserted into a layer composed of electroneutral lipids the electrostatic interaction, in spite of the long-range character, can be limited to the nearest neighbour interaction. Computer simulation results suggest, that the gel-fluid transition temperature can be lowered or raised by a proper selection of anionic-cationic amphiphilic modifiers. Moreover, the effect of ionic strength of the membrane medium and dielectric permeability of the hydrophobic part of membrane, where a shift of the dielectric constant from 5 to 80 occurred, has been studied. It was also shown that addition of alkyl molecules to the membrane, which are the counterions of alkyl modifier molecules added earlier, almost doubles the number of incorporated membrane modifiers. Membrane permeability analysis shows that membrane permeability, at temperatures lower than the gel-fluid transition temperature, should be more related to the number of small domains (cluster area) and less to the interfacial area.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1998, 2, 4; 601-609
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-14 z 14

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