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Wyświetlanie 1-15 z 17
Tytuł:
A digital cartographic source for numerical models in hydrology
Autorzy:
Szpakowski, W.
Szulwic, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933151.pdf
Data publikacji:
2007
Wydawca:
Politechnika Gdańska
Tematy:
digital cartography
GIS
numerical simulation
Opis:
A short review of digital data used in hydrological models is presented. There are three basic kinds of digital maps used in hydrology: raster images (scan, orthophotomap), vector maps and digital models (Digital Terrain, Landscape and Elevation Models). Hydrological models are used to analyze natural phenomena: free surface flow, the precipitation-outflow relation and groundwater flow. The choice of cartographic source depends on the problem to be solved. The article includes an analysis of two problems: (i) the solution of flood area due to extreme river flow and (ii) groundwater flow. In both cases, digital cartographic sources are presented.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2007, 11, 4; 449-461
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical investigation of flooding of real-topography developed areas following river embankment failure
Autorzy:
Szydłowski, M.
Twaróg, B.
Powiązania:
https://bibliotekanauki.pl/articles/1955326.pdf
Data publikacji:
2006
Wydawca:
Politechnika Gdańska
Tematy:
numerical simulation
river embankment failure
inundation
developed area
Opis:
The paper concerns numerical simulations of flood wave propagation in an urban area resulting from a river embankment failure. Simulations have been performed to predict and analyze the parameters of flash and catastrophic flow in a developed area with the aim of presenting numerical calculations useful for identification of inundation zones. The shallow water equations were assumed as the mathematical model of free-surface unsteady water flow. A numerical scheme of the finite volume method was applied to solve the model equations and the Roe method used to approximate the mass and momentum fluxes. Two test cases of embankment failure are investigated in the paper. The aim of one experiment is to simulate a flood in a model city area, where a group of buildings representing a simplified urban configuration was introduced. In order to verify the calculations, numerical results were examined against experimental data available from laboratory measurements. An experiment of the model city's flooding event was carried out at the hydraulic laboratory of the Gdansk University of Technology. The other test case concerns flash flood simulation on an embanked developed area of real topography.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2006, 10, 3; 321-338
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of transient flow in storm sewers using standard and improved McCormack scheme
Autorzy:
Szydłowski, M.
Machalińska-Murawska, J.
Powiązania:
https://bibliotekanauki.pl/articles/1933987.pdf
Data publikacji:
2012
Wydawca:
Politechnika Gdańska
Tematy:
mathematical modeling
numerical simulation
transient flow
storm sewers
Opis:
This paper describes the results of the first part of the research project which aims at developing a hydraulic model for simulation of unsteady flows in storm sewers ranging from gravity flows to surcharged flows resulting with water outflow on the ground surface and propagation of inundation in the flooded area. The paper focuses on the development and assessment of a second-order explicit numerical scheme for unsteady flows in sewers, but only in a single pipe at this moment, without any special elements such as manholes or drop shafts and with no water overflowing problem. The problem of water flow in sewer system pipes is associated with some specific phenomena occurring in conduits during storm events. If the pipes start to be fully filled with water, there is a transition from free surface to pressurized flow. Then, the vice versa effect can be observed. Such transitions are also possible in sewers when the discharge is controlled by control devices, such as gates for example. Moreover, the rapidly varied flow with some hydraulic local effects such as hydraulic jumps or bores can appear during extreme rain episodes. The appropriate modeling techniques have to be applied to solve these problems. The ‘Preissmann slot’ concept is implemented to simulate the pressurized flow. The original and improved McCormack scheme is used for transcritical flow simulation. The calculated results obtained for some benchmark tests are compared with numerical solutions and laboratory measurements published in the technical literature.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2012, 16, 1-2; 53-74
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations by Godunov-type schemes of air-pollutant dynamics
Autorzy:
Murawski, K.
Michalczyk, J. K.
Powiązania:
https://bibliotekanauki.pl/articles/1955805.pdf
Data publikacji:
2001
Wydawca:
Politechnika Gdańska
Tematy:
numerical simulation
numerical discretization
hydrodynamic equations
distrubution of air-pollutants
Opis:
In this paper several aspects associated with numerical simulations of hyperbolic equations are discussed. This presentation covers a range of modern shock-capturing schemes which are based on Godunov-type techniques. These schemes are well suited for strong shocks and other discontinuities, without generating spurious oscillations in the flow variables. An example of a performance of such schemes is provided to simulate the spatial distribution of air-pollutants which are emitted from a chimney. The simulations are performed in the framework of two-dimensional hydrodynamics, with a use of the CLAWPACK code (R.J.LeVeque, CLAWPACK User Notes, Applied Mathematics,Univ. of Washington, Seattle, 1997a). The model reproduces several features of the distribution, including occurrence of vortices and plumes above the chimney.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2001, 5, 2; 207-228
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of spontaneously condensing flows in a plane turbine cascade
Autorzy:
Li, L.
Li, G.
Feng, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1986685.pdf
Data publikacji:
2002
Wydawca:
Politechnika Gdańska
Tematy:
wet steam
condensing flow
Eulerian/Eulerian model
numerical simulation
Opis:
The low efficiency of wet steam turbine is mainly attributed to wetness losses. To investigate the mechanisms which give rise to these losses, a fully Eulerian model has been developed for calculation of the wet steam flows with spontaneous condensation. In this model, the liquid phase is described with two conservation equations in Eulerian form and coupled with a solver of gas dynamics equations. With such a model, the existing code for simulation of single-phase flows can easily be changed to include wet steam two-phase flows in wet steam turbines. A numerical simulation of condensing flow in a plane turbine cascade is performed, and the numerical results are presented and compared with the experimental results.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2002, 6, 1; 209-216
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical analysis of the tip vortex in an air-conditioners propeller fan
Autorzy:
Wang, J.
Wu, K.
Powiązania:
https://bibliotekanauki.pl/articles/1955218.pdf
Data publikacji:
2006
Wydawca:
Politechnika Gdańska
Tematy:
tip vortex
internal flow field
propeller fan
numerical simulation
Opis:
A steady, incompressible, turbulent flow field inside a propeller fan used in an air conditioner has been analyzed numerically using the single-equation Spalart-Allmaras turbulence model. It has been found that the formation of tip vortex starts from the blade tip's suction side at about one third of the axial chord's length aft of the rotor's leading edge. It is due to the rolling-up of the intense shear layer flow between the main axial flow and the suck-in inward flow caused by the large pressure difference between the pressure and the suction sides. The tip vortex passes through the blade passage in a curve reversed towards the direction of the blade's rotation. Its trace is partial to the tangential direction as it goes into the aft part of the blade passage covered by the shroud and, simultaneously, its trace in the radial direction is turned from the outward direction to the inward direction. The operating flow rates have an important effect on the axial position of the tip vor-tex's trace, while its effect on the radial position is negligible. At law flow rates, the vortex disappears at a location closer to the leading edge. The effect of the shroud's width on the tip vortex's trajectory is notable. For a fan with a wide shroud, the trace of the tip vortex moves upstream with a smaller radial influence region than that of a fan with a narrower shroud.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2006, 10, 2; 101-112
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of open channel flow between bridge piers
Autorzy:
Szydłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1934025.pdf
Data publikacji:
2011
Wydawca:
Politechnika Gdańska
Tematy:
numerical simulation
open channel flow
mathematical modeling
bridge piers
Opis:
Free-surface flow in the vicinity of bridge piers on a fixed channel bed is a classical problem of open-channel hydraulics. This problem is usually analyzed using one-dimensional hydraulic models for steady-flow problems. The aim of this paper is to present a two-dimensional numerical simulation of water flow around obstacles, such as cylinders, which can act as a simplified model of real piers. The depth-averaged Navier-Stokes equations describing unsteady free-surface flow are solved using an explicit scheme of the finite-volume method. The numerical solution prepared for the simulations of unsteady free-surface flows was used here to analyze the case of steady flow. A numerical simulation of flow in the channel with the obstruction was performed for two different inflow discharges determining, respectively, the subcritical and supercritical flow in the cross-section of a channel constriction. In the second simulation, a hydraulic jump was observed downstream of the bridge section. The numerical results were compared with measurements. Water surface profiles were measured for both discharges in the hydraulic laboratory of the Faculty of Civil and Environmental Engineering at Gdansk University of Technology (GUT). Comparisons with laboratory data showed that the proposed approach constitutes a sufficiently accurate and reliable technique for predicting basic flow parameters. The method of two-dimensional modeling of flow in a river channel between bridge piers can be also integrated with the simulation of unsteady flood wave propagation, ensuring a uniform approach to the problem of flood modeling in river valleys. Moreover, a two-dimensional simulation yields detailed information about flow structure near the obstruction, which can be used to better elucidate debris transport and river bed deformation processes.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2011, 15, 3-4; 271-282
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation and modification of 3D flow phenomena in an axial flow fan
Autorzy:
Elhadi, E. E.
Keqi, W.
Powiązania:
https://bibliotekanauki.pl/articles/1954658.pdf
Data publikacji:
2003
Wydawca:
Politechnika Gdańska
Tematy:
axial flow fan
vortex
stagger angle
numerical simulation
3D
Opis:
This work aims to study and analyze the behavior of flow in an axial flow fan using numerical simulation based on solving Reynolds-averaged Navier-Stokes equations coupled with a modified Spalart-Allaras turbulence model. In the present work, different flow phenomena occuring in an axial flow fan were presented and interpreted at different design conditions and at different regions, with special concern to the rotor exit and stator regions. Large vortices and reverse flow at the stator suction side were observed under high loading conditions. These are mainly due to radial and centrifugal effects in the fluid due to a decreasing flow rate. To avoid this type of flow, the stator flow pattern has been modified using a new stator blade. This blade was designed by changing the stator stagger angle by 10o in the radial direction. This study indicates that the flow in the modified stator region behaves well and gives better performance than that obtained when using a baseline stator, especially under high loading conditions. This study also indicates that the stator stagger angle has a significant effect on modifying the fan performance.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2003, 7, 2; 199-213
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulation of the blade cascade flows using upwind methods
Autorzy:
Chmielniak, T. J.
Wróblewski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1953981.pdf
Data publikacji:
1998
Wydawca:
Politechnika Gdańska
Tematy:
numerical simulation
turbomachinery cascades
finite volume discretisation
upwind-biased technique
Opis:
A mathematical formulation of the equations of fluid motion in turbomachinery cascades has been presented. A review of the calculation methods for solving these equations is given. These methods are based on an explicit time marching scheme with finite volume discretisation and upwind-biased technique for the inviscid fluxes calculations. The high order accuracy in space is realized by the MUSCL approximation. The discretisation methods and numerical grids are described. The calculations of viscous and inviscid flow models are performed. The model and results of the water steam flow analysis with homogeneous condensation are presented. The calculations are performed for complex problems of real blade configurations of turbomachinery.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1998, 2, 2; 287-317
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Lattice Boltzmann method for fluid mixing: a comparison with the finite element method
Autorzy:
Egidi, N.
Misici, L.
Piergallini, R.
Tosi, F.
Powiązania:
https://bibliotekanauki.pl/articles/1955715.pdf
Data publikacji:
2004
Wydawca:
Politechnika Gdańska
Tematy:
lattice Boltzmann method
incompressible viscous fluid mixing
Reynolds number
numerical simulation
Opis:
In this article we study three-dimensional mixing of an incompressible viscous fluid subjected to the force of rotating blades in a vessel, with a low Reynolds number. The results obtained with the lattice Boltzmann method are compared with the ones previously obtained using the finite element method. All the qualitative and quantitative parameters of the two simulations agree.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 1; 5-15
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Shear band development in modified DEM: importance of couple stress
Autorzy:
Iwashita, K.
Oda, M.
Powiązania:
https://bibliotekanauki.pl/articles/1953963.pdf
Data publikacji:
1998
Wydawca:
Politechnika Gdańska
Tematy:
shear band development
distinct element method
couple stress
numerical simulation tests
Opis:
Numerical simulation tests were carried out using the distinct element method (DEM) with great interest in how large couple stress is actually generated in a shear band. To do this, the conventional DEM was modified slightly, so that the effect of rolling resistance at contact points can be taken into account (called MDEM). It has been found that MDEM provides a powerful tool in simulating not only the generation of large voids inside a shear band but also the high gradient of particle rotation along the shear band boundaries, in a quite similar manner to those of natural granular soils; and that couple stress, although it is very small, is certainly developed in a consistent manner with the particle relation gradient developed in a shear band.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1998, 2, 3; 443-460
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transient cavitating pipe flow: Computation models and methods
Autorzy:
Urbanowicz, K.
Zarzycki, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1943252.pdf
Data publikacji:
2008
Wydawca:
Politechnika Gdańska
Tematy:
column separation
bubby flow
numerical simulation
cavitation
transient turbulent pipe flow
unsteady friction
Opis:
The paper presents four key mathematical models of a transient cavitating pipe flow, i.e. the column separation model (CSM), the gas cavitation model (CSMG), Adamkowski’s model (CSMA) and the bubbly cavitation model (BCM). All models investigated in the paper take into account unsteady frictional loss models. The equations describing all models have been solved using the method of characteristics at first and the finite differences method then. The results of numerical simulations have been compared with the results obtained in the experiments. Transients which have taken into account the unsteady wall shear stress fit well with the results of experiments in comparison with the quasi-steady wall shear stress model.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2008, 12, 3-4; 159-172
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulations of the water freezing process: numerical benchmarks
Autorzy:
Michałek, T.
Kowalewski, T. A.
Powiązania:
https://bibliotekanauki.pl/articles/1955733.pdf
Data publikacji:
2003
Wydawca:
Politechnika Gdańska
Tematy:
numerical simulation
numerical benchmarks
finite volume method
fixed grid enthalpyporosity method
volume of fluid
solidification
free surface flow
Opis:
Three numerical benchmarks concerning the freezing of water in small enclosures are analysed using the commercial FLUENT code. The first case is a steady-state natural convection in a differentially heated cavity for temperatures near the freezing point. In the second case, the freezing of water in a differentially heated cavity is simulated. The third case describes a simulation of freezing water in the presence of forced convection and a free surface flow. Two finite-differences numerical codes are used to verify results of the FLUENT simulations for the natural convection and solidification in the differentially heated cavity. It is found that the simulation of water solidification requires very fine meshes and short time steps, extending the computational time to the extreme.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2003, 7, 3; 389-408
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:
Applicability of flow simulation models to the case of radial inflow onto a rotating core
Autorzy:
Biernacki, R.
Powiązania:
https://bibliotekanauki.pl/articles/1955813.pdf
Data publikacji:
2001
Wydawca:
Politechnika Gdańska
Tematy:
turbulent flow
numerical flow simulation
flow simulation models
steam turbines
turbine inlet
computational fluid dynamics CFD
Opis:
The paper presents the results of fluid flow simulations carried out by means of the FIDAP7.6 program (a fluid dynamics FEM package) for the case of radial inflow onto a rotating shaft. The particular geometric configuration has been chosen to resemble a generalized inlet chamber of twin low-pressure steam turbines, but with the axial outlet section extended to allow better observation of flow instabilities in that region. The calculations were carried out for the same channel geometry for both compressible and incompressible flow, using the same or slightly varying boundary conditions. Extensive variation in non-physical parameters of the model was explored, such as applying different meshes over the region, as well as utilizing different turbulence and upwinding models. The intent of this research was to evaluate the relative applicability of the various available flow models to the simulation of axisymmetric flows with steep velocity gradients, and to discover the limitations of these models. The calculations have in fact established significant differences in the behavior of the simulated flow for the different meshes and models. Some results were characterized by extensive areas of recirculating flow whereas others, for the same boundary conditions, showed no recirculation. Correct near-wall meshing as well as the choice of the upwinding scheme were established as the critical factors in this regard. There was also noticeable variation in outlet velocity profiles. An extensive zone of separation within the investigated channel as well as a standing annular vortex near the point of stagnation are flow features of some interest. These patterns of flow change in response to the changing non-physical parameters; the separation zone in particular is absent or slow to develop under some setups. The influence of inflow parameters, the initial velocity distribution and turbulent intensity in particular, on flow behavior in contact with the rotating shaft have also been an area of investigation, as these are often defined with considerable uncertainty in practical applications. It was observed that some latitude in assuming these parameters did not significantly alter the relevant flow parameters at outlet (the velocity and pressure distributions), although it did induce variation in other aspects of the flow (such as the extent of the standing vortex).
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2001, 5, 2; 141-154
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 17

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