Ograniczanie wyników
Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 103

Liczba wyników na stronie
first rewind previous Strona / 6 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  fluid flow
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 6 next fast forward last
PL
Rozpoznanie występującego w przewodzie rozmieszczenia faz jest niezbędne do stworzenia odpowiedniego modelu hydrodynamicznego. W pracy wykorzystano uczenie maszynowe do identyfikacji kryteriów przepływów płynów dwufazowych w przewodach horyzontalnych. Wykorzystując filmy z przepływami stworzono zbiór danych uczących i walidacyjnych, sklasyfikowanych w pięciu klastrach odpowiadających następującym strukturom przepływu: pęcherzykowej, rzutowej, korkowej, warstwowej i falowej. Następnie opracowano modele uczenia maszynowego z wykorzystaniem bibliotek TensorFlow oraz Keras, w których wykorzystano głębokie warstwy konwolucyjne. Finalnie wytypowano optymalną budowę sieci neuronowej, która zapewniała niskie wartości parametru straty i wysoką dokładność klasyfikacji. Zaproponowane rozwiązanie może znaleźć zastosowanie w przemyśle konkurując z wykorzystywanymi obecnie.
EN
Recognition of the phase distribution in pipe is necessary to create the appropriate hydrodynamic model. In the thesis, machine learning was used to identify flow regime for two-phase fluids in horizontal pipes. Using films with flows, a set of learning and validation data was created and classified in five clusters corresponding to the following flow structures: bubbly, slug, plug, stratified and wavy. Then, machine learning models were developed, using the TensorFlow and Keras libraries, which used deep convolution layers. Finally, the optimal structure of the neural network was proposed, which ensured low values of the loss parameter and high accuracy of classification. The proposed solution may find application in industry competing with those currently used.
2
Content available remote Obtaining fluid flow pattern for turbine stage with neural model
EN
In the paper possibility of applying neural model to obtaining patterns of proper operation for fluid flow in turbine stagefor fluid-flow diagnostics is discussed. Main differences between Computational Fluid Dynamics (CFD) solvers and neural model is given, also limitations and advantages of both are considered. Time of calculations of both methods was given, also possibilities of shortening that time with preserving the accuracy of the calculations are discussed. Gathering training data set and neural networks architecture is presented in detail. Range of work of neural model was given. Required input data for neural model and reason why it is different than in computational fluid dynamics solvers isexplained. Results obtained with neural model in 21 tests are discussed. Arithmetic mean and median of relative errors of recreating distribution of pressure and temperature are shown. Achieved results are analysed.
EN
The flat tubes are necessary apparatus to design the modern heat exchangers. In this context, a CFD (computational fluid dynamics) study has been achieved to explore the influence of the flat tube size on the heat transfer characteristics in cross-flow over flat tube banks. The calculations are performed with the help of the computer software (Fluent) which is based on the finite volume method to solve the continuity, momentum and energy equations. The numerical investigations are achieved for laminar flow (Reynolds numbers changing from 50 to 800), two dimensional flows and incompressible fluids. Some predicted results are compared with available experimental data of the literature and a satisfactory agreement is observed. The obtained results show a decrease in the heat transfer coefficient with increased size of the flat tube. A new valuable empirical correlation is suggested for the prediction of heat transfer coefficients over a flat tube bank. The proposed correlation may be useful for engineers to predict the heat transfer rates in such devices without requirements of experimental measurements.
PL
W artykule przedstawiono główne założenia modelu matematycznego przepływu ciekłej stali sprzężonego z modelem krzepnięcia. Prezentowane rozwiązanie bazuje na metodzie hydrodynamiki cząstek rozmytych i stanowi pierwszy etap prac rozwojowych zmierzających do opracowania kompleksowego modelu odkształcania stali w stanie półciekłym. Docelowo opracowany model numeryczny umożliwi symulację odkształcania stali w warunkach współistnienia fazy ciekłej i stałej, z uwzględnieniem lokalnych przepływów krzepnącej stali w obrębie zestalonego szkieletu fazy stałej. Implementacja numeryczna modułu obliczeniowego hydrodynamiki cząstek rozmytych realizowana jest w ramach rozwijanego od kilkunastu lat autorskiego pakietu DEFFEM 3D. Uzupełnienie pracy stanowią przykładowe wyniki symulacji testowych wskazujących na poprawność przyjętych założeń modelowych.
EN
The article presents the main assumptions of the mathematical model of liquid steel flow coupled with the solidification model. The presented solution is based on the smoothed particle hydrodynamics method and is the first stage of development works aimed at developing a comprehensive model of steel deformation in the semi-solid state. Ultimately developed numerical model will enable simulation of steel deformation in the semi-solid state, taking into account local flows of solidifying steel within a solidified solid phase skeleton. The numerical implementation of the SPH solver is carried out as part of the DEFFEM 3D package being developed for over a dozen years. The supplements to the work are exemplary results of test simulations indicating the correctness of the adopted model assumptions.
5
Content available Flow velocity measurements in the open channels
EN
Badanie skierowane na wyznaczenie zależności pomiędzy wysokością nadchodzącej fali a prędkością strumienia w otwartych kanałach z użyciem narzędzi widzenia komputerowego. Autorzy korzystają z modelowania komputerowego oraz badań eksperymentalnych do sprawdzenia możliwości wyznaczenia prędkości strumienia poprzez pomiar wysokość fali padającej na częściowo zanurzoną sztuczną przeszkodę znajdującą się na otwartym kanale.
EN
Electromagnetic stirrer generates swirling fluid flow, boosts the mixing of molten steel near the solidification front and enhances the quality of the continuously cast products. In the present investigation, attention is paid towards studying the effect of in-mold electromagnetic stirring on fluid flow and solidification. A three-dimensional coupled mathematical model of solidification and magnetohydrodynamics has been established for billet caster mold. The alternating magnetic field is applied to the solidification model where fluid flow, heat transfer, and electromagnetic equations are solved simultaneously. It has been found that an increase in field frequency decreases the length of stirring and the liquid fraction of the steel at the center of the mold exit. Tangential velocity near the solidification front increases with the magnetic field frequency or flux density, due to which, a break in solidified shell near stirrer position is predicted whose width increases accordingly.
7
Content available remote Hybrid model of liquid metal flow and solidification
EN
The article presents a hybrid model dedicated to simulations of liquid metal flow and its solidification. The developed solution is a key component of the developed integrated modelling concept, which combines the advantages of physical and computer simulations, while the concept itself is the foundation of a scientific workshop oriented at high-temperature processes (close to solidus lines). Examples of test simulation results are presented, indicating that the adopted model assumptions are correct.
PL
W artykule przedstawiono hybrydowy model dedykowany symulacjom przepływu ciekłego metalu i krzepnięcia. Opracowane rozwiązanie jest kluczowym elementem rozwijanej koncpecji zintegrowanego modelowania łączącego zalety symulacji fizycznej i komputerowej, zaś sama koncepcja stanowi fundament warsztatu naukowego zorientowanego na procesy wysokotemperaturowe (bliskich linii solidus). Przedstawiono przykładowe wyniki symulacji testowych, wskazujących na poprawność przyjętych założeń modelowych.
8
Content available Simulation of complex logistical service processes
EN
The world around us is a very complex and multi-parametric system, like the weather, traffic, operation of machines, production processes, service processes, etc. Understanding of the characteristics, operation and behaviour of these systems and processes is not easy due to their complexity. The design of optimal production and service procedures is an essential task for planners. The target is the increasing of the efficiency of the production and service and analysis of the effect of parameter changing. There are lot of tools and sophisticated methods for design, analysis and improvement of logistical processes. The most often used analysis tool is the simulation in the production processes. Our aim in this article is to show that the simulation can be used efficiently in case of analysis of service processes, not only in case of production processes. The simulation is available for bottleneck analysis of service activities not only for production processes. In this study the simulation of a service process was realized by the AnyLogic software. The relevance of the simulation technique for analysis of complex service processes is proved by a case study of a service and maintenance activity of a multinational shopping centre.
9
Content available remote 3D Numerical Simulation of Laminar Flow and Conjugate Heat Transfer through Fabric
EN
The air flow and conjugate heat transfer through the fabric was investigated numerically. The objective of this paper is to study the thermal insulation of fabrics under heat convection or the heat loss of human body under different conditions (fabric structure and contact conditions between the human skin and the fabric). The numerical simulations were performed in laminar flow regime at constant skin temperature (310 K) and constant air flow temperature (273 K) at a speed of 5 m/s. Some important parameters such as heat flux through the fabrics, heat transfer coefficient, and Nusselt number were evaluated. The results showed that the heat loss from human body (the heat transfer coefficient) was smallest or the thermal insulation of fabric was highest when the fabric had no pores and no contact with the human skin, the heat loss from human body (the heat transfer coefficient) was highest when the fabric had pores and the air flow penetrated through the fabric.
10
PL
Przedstawiono wpływ parametru geometrycznego (średnicy rury cyrkulacyjnej) na wybrane parametry hybrydowego reaktora airlift. Przedstawiono także doświadczalną weryfikację wpływu tej średnicy oraz porównano otrzymane wyniki doświadczalne z zaproponowanym modelem hydrodynamiki reaktora. Analizowany reaktor jest połączeniem aparatu fluidyzacyjnego i aparatu airlift. Nie jest to jednak typowy trójfazowy reaktor fluidyzacyjny, gdyż nie ma w nim kontaktu fazy stałej i gazowej. Zaproponowany model oparto na globalnym bilansie pędu oraz bilansach masy cieczy i gazu. Weryfikacja doświadczalna modelu została przeprowadzona przez pomiar stopnia zatrzymania gazu w strefie barbotażu za pomocą metody manometrycznej, pomiar prędkości przepływu cieczy w rurze cyrkulacyjnej oraz pomiar dynamicznej wysokości złoża.
EN
Effect of circulation pipe diam. on the selected flow para- meters of the hybrid airlift reactor was computed from a developed math. hydrodynamic model and exptl. verified. The apparatus consisted of a fluidized bed reactor and an airlift reactor. It was not a typical 3-phase airlift reactor, because the contact between solid and gas phases did not occur. The developed model was based on the global momentum balance and mass balances of the gas and liq. Exptl. verification of the model was carried out by the measurements of gas hold-up in the bubbling zone (manometric method), liq. flow velocity in the downcomer and fluidized bed height.
11
Content available remote Performance Evaluation of Multipurpose Solar Heating System
EN
In order to increase the heat transfer and thermal performance of solar collectors, a multipurpose solar collector is designed and investigated experimentally by combining the solar water collector and solar air collector. In this design, the storage tank of the conventional solar water collector is modified as riser tubes and header and is fitted in the bottom of the solar air heater. This paper presents the study of fluid flow and heat transfer in a multipurpose solar air heater by using Computational Fluid Dynamics (CFD) which reduces time and cost. The result reveals that in the multipurpose solar air heater at load condition, for flow rate of 0.0176 m3/s m2, the maximum average thermal efficiency was 73.06% for summer and 67.15 % for winter season. In multipurpose solar air heating system, the simulated results are compared to experimental values and the deviation falls within ± 11.61% for summer season and ± 10.64% for winter season. It proves that the simulated (CFD) results falls within the acceptable limits.
EN
Cu–4.7 wt. % Sn alloy wire with Ø10 mm was prepared by two-phase zone continuous casting technology, and the temperature field, heat and fluid flow were investigated by the numerical simulated method. As the melting temperature, mold temperature, continuous casting speed and cooling water temperature is 1200°C, 1040°C, 20 mm/min and 18°C, respectively, the alloy temperature in the mold is in the range of 720°C–1081°C, and the solid/liquid interface is in the mold. In the center of the mold, the heat flow direction is vertically downward. At the upper wall of the mold, the heat flow direction is obliquely downward and deflects toward the mold, and at the lower wall of the mold, the heat flow deflects toward the alloy. There is a complex circular flow in the mold. Liquid alloy flows downward along the wall of the mold and flows upward in the center.
13
Content available remote Wizualizacja przepływu cieczy w kanale metodą PIV
EN
Fluid flows in test station can be investigated using methods of flow visualization witch computer – aided processing of flow images. Test station are presented of the investigation using the method of particle image velocimetry (PIV), of liquid flow in plexiglas channel. For the test example of flow around a cylinder in test station.
14
Content available remote Badania numeryczne przepływu płynu przez rotametr
EN
In this paper are presented fluid flows around the float in the rotameter. The author used the commercial computer software from CFD group. The calculation meshed was created for selected float shapes in two and three-dimensional graphics with use Ansys Fluent package. The author analyzed the behavior of the forces working on the float, the pressure distribution and velocity of fluids.
EN
Deformation bands and microfractures occurring in sandstones affect the petrophysical properties of the rock and determine fluid flow. Deformation bands are quasi-tabular structures, up to 5 mm thick that accommodate offsets on the order of a few centimeters (Fossen 2010). Such bands show different petrophysical properties in relation to the surrounding rocks and may function as either a path or a barrier to the migrating fluids (Antonellini et al. 1994, Fossen 2010). High porosity rocks show commonly low permeability due to the presence of deformation bands. Recognition of such relationships is important in petroleum geology, particularly for proper reservoir characterization (e.g. Fossen et al. 2007, Ballas et al. 2012, 2013). The aim of the study is to identify and to characterize deformation bands occurring in flysch sandstones of the Outer Carpathians using X-ray nanotomography and nuclear magnetic resonance (NMR). Moreover, the impact of sample size on obtained results was also studied. For this study, samples of medium-grained arenites showing catalclastic deformation bands have been collected from the lower Krosno Beds of the Silesian Nappe. Permeability of the studied samples measured along deformation bands and in perpendicular direction varies significantly, being 0.13 mD and <0.001 mD, respectively. Analyses were conducted using X-ray nanotomography Nanotom S General Electric. The recorded data were processed and analyzed using ImageJ and myVGL software. The NMR measurements were carried out on water-saturated samples using the 2MHz Magritek Rock Core Analyzer and 24MHz Tomography System. The pore size distribution (PSD) of the rock sample was determined precisely by T2CMPG experiments. The spatial estimation of the deformation bands achieved from T2 spatially resolved measurements. Complementary data regarding to band geometry was registered using three-dimensional Single Point Imaging (SPI) (comp. Zhang & Blümich 2014). Cylindrical plugs38 mm high and 25 mm in diameter were analysed. The same plugs were used for permeability measurements. The X-ray nanotomography measurements were carried out in three resolutions. The first measurement was carried out with a resolution of 4.2 microns, but the resultant images were difficult to interpret. Therefore, successive analyses were performed with a resolution of 20 microns covering the entire volume of the samples. After locating microstructures samples were X-rayed again with a resolution of 2.1 microns. In sections obtained at a resolution of 4.2 microns, fine structure attributable to deformation band reveals parallel grain orientation and higher density compared with the host sandstone. We observed a slight offset along deformation bands. Three-dimensional image of the sample obtained at a resolution of 20 microns determined the geometry of tectonic microstructures. In one of samples, two structures were recognized. One of them was oriented parallel to the axis of the core, the other was inclined at an angle of about 60 degrees. The thickness of deformation band visible in the cylindrical plug was much larger (2 mm) than the thickness of the surface obtained by visualization. This was due to the presence of microfractures, which formed along the deformation band. Measurement with a resolution of 2.1 microns took an upper base of the cylindrical plug. Two thin fractures and one relatively thick fracture (approx. 0.2 mm) were distinguished. This indicates that the deformation band visible on the surface of the core passes into the microfracture within the sample. It was also confirmed by the visualization with a resolution of 20 microns. Determination of porosity and permeability of the sandstone using the X-ray nanotomograph was impossible due to small pore size that the device is not able to register. However, visualization made with a resolution of 20 microns allowed to clarify the reasons for the different measurements of permeability. Increase of the permeability in the direction parallel to the axis of the core is caused by the presence of open microfractures. The NMR results confirmed possibility to visualize geometry of the bands and their influence for the spatial distribution of porosity. The results show that too large sample sizes make impossible to perform the analysis with high resolution. According to Rodrigues et al. (2015) sample dimensions of 15 × 10 × 10 mm are sufficient to determine the porosity of deformation bands. Published results on three-dimensional micro-tomography of deformation bands concern aeolian sandstones showing high mineralogical and textural maturity (Rodrigues et al. 2015). In contrast, studied flysch sandstones show large diversity of their mineral composition. Therefore, visualization of microtectonic deformation hosted in these sandstones is more difficult to interpret.
EN
Joining metals and alloys with different properties gives greater flexibility in design and production as compared to manufacturing with one type of material only. Thanks to this, expensive materials can be applied only at places where their use is indispensable. However, joining different combinations of metals become a challenge, due to the differences in physical and chemical properties. Laser welding, thanks to such advantages as good weldability and high quality of joints with narrow heat affected zone, allows for solving many problems appearing in traditional joining methods. The current paper concerns modelling of laser welding processes for materials with different physical and chemical properties. The model consists of a coupled set of incompressible fluid flow equations, heat equation and convection-diffusion equations for different material species. The formulation takes into account the dependence of material properties on temperature and chemical composition. Discontinuity of density and viscosity, together with the chemical composition of fluid in weld pool influences the velocity and temperature distribution in the weld pool and in consequence determines the shape and properties of a joint.
PL
Artykuł dotyczy modelowania spawania laserowego materiałów o różnych własnościach. Dominującą siłą wymuszającą ruch cieczy w takich układach jest gradient napięcia powierzchniowego oraz siła odrzutu powstała na powierzchni jeziorka spawalniczego. W literaturze można znaleźć wiele artykułów w których wykorzystano różne metody śledzenia powierzchni międzyfazowej, np. Level Set method (LS), Volume of Fluid method (VOF), lub bardziej skomplikowanej Coupled Level Set and Volume of Fluid method (CLSVOF). W wielu publikacjach wykorzystywana jest metoda VOF. Metoda ta jest wydajna, ponieważ nie wymaga iteracyjnego rozwiązywania dodatkowych równań i spełnia zasadę zachowania masy. Niestety metoda ta nie pozwala na wyznaczenie dokładnego położenia powierzchni międzyfazowej. Granica międzyfazowa jest rekonstruowana w każdej iteracji za pomocą pola udziału fazy, dyskretyzowanego na siatce eulerowskiej. Wartość tego pola wskazuje jaka faza znajduje się w danej komórce siatki. Granica międzyfazowa przemieszcza się przez adwekcję pola fazowego. Przyczyną trudności może być wymaganie dużej dokładności wyznaczenia położenia granicy w każdej iteracji rozwiązania. To z kolei powoduje nieciągłość własności takich jak gęstość i lepkość na granicy międzyfazowej, a przez to niestabilność numeryczną rozwiązania. Metoda VOF spełnia warunek zachowania masy. Pochodne pola udziału fazy VOF nie są jednak ciągłe w okolicy granicy międzyfazowej. Dlatego obliczone z funkcji fazy VOF krzywizna granicy i wektor normalny do granicy są niedokładne. Powoduje to tworzenie się w obszarze granicznym pozornych przepływów w wyniku niezrównoważenia siły napięcia powierzchniowego. Artykuł dotyczy wykorzystania powyższych metod do modelowania spawania laserowego materiałów o różnych własnościach fizycznych. Spawanie takich materiałów jest trudne, ze względu na tworzenie się asymetrii w przepływach ciepła i masy oraz zauważalną segregację pierwiastków powierzchniowo aktywnych. Tworząca się mikrostruktura zespawanych elementów przez to także jest asymetryczna względem płaszczyzny spawania. Modelowanie takich przepływów pozwoli na zrozumienie procesów zachodzących w jeziorku spawalniczym.
EN
This paper concerns the mathematical and numerical modelling of thermal phenomena and phase transformations in the solid state accompanying laser heating processes. Thermal phenomena with the motion of a liquid metal in the fusion zone are analyzed on the basis of numerical solution of equations for mass, momentum and energy conservation. Phase transformations in solid state are estimated using classic models of the kinetics of phase transformations as well as continuous heating transformations (CHT) and continuous cooling transformations (CCT) diagrams for S355 steel. Computer simulations are executed for the laser welding process in order to predict the influence of welding speed on the structural composition as well as thermal and structural strains in the joint.
EN
This paper presents the numerical results of a numerical analysis of drilling fluid flow through annular space in the borehole. The analysis used the Herschel–Bulkley rheological fluid model. The obtained results of the analysis for three cases with variable geometry. Variable geometry is associated with a larger diameter drill in the joints of drill pipes, and consequently, with reduced flow cross-section. A comparison of pressure values at the end of the analyzed examples showed that in the example of a simple drill pipe without joints, pressure values were 30% higher than in the case, which takes into account changes in the geometry of the joints.
19
Content available remote Metody wizualizacji przepływu płynów
EN
Research of phenomena occurring during the movement of the fluid in the pipes belong to the complex issues of fluid mechanics. There are methods for observing the fluid flow phenomena, for them to fluid flow visualization. The article described are methods for the visualization of fluid flow and types of tracer particles.
20
Content available Mathematical modeling of fluid flow in brain tumor
EN
We consider the problem of fluid flow in a brain tumor. We develop a mathematical model for the one-dimensional fluid flow in a spherical tumor where the spatial variations of the interstitial velocity, interstitial pressure and the drug concentration within the tumor are only with respect to the radial distance from the center of the tumor. The interstitial ve- locity in the radial direction and the interstitial pressure are determined analytically, while the radial variations of two investigated drug concentrations were determined numerically. We calculated these quantities in the tumor, in a corresponding normal tissue and for the concentrations also in the cavity that can exist after the tumor is removed. We determine, in particular, the way the interstitial pressure and velocity vary, which agrees with the expe- riments, as well as the way one drug concentration changes in the presence or absence of a second drug concentration within the tumor. We find that the amount of drug delivery in the tumor can be enhanced in the presence of another drug in the tumor, while the ratio of the amount of one drug in the tumor to its amount in the normal tissue can be reduced in the presence of the second drug in the tumor and the tissue.
first rewind previous Strona / 6 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.