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Wyniki wyszukiwania dla: TWO-DIMENSIONAL MODELING OF FLOWS, BI-HARMONIC HELMHOLTZ EQUATION, HYDRODYNAMICS OF WATER FLOW
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Measurements of Two-phase Flows in Pipelines Using Radioisotopes and Statistical Signal Processing
PublikacjaThis paper presents an application of radiotracers and gamma absorption method in two-phase flow measurements in pipelines. Two different methods were implemented to analysis of acquired signals. Investigated methods are based on the cross-correlation function and the phase of the cross-spectral density distribution. The examples presented in the article illustrate the application of the radioisotopes to evaluation of liquid-gas...
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Acoustic Hysteresis in Flows with Different Kinds of Relaxation and Attenuation
PublikacjaGraphs in the thermodynamic plane acoustic pressure versus excess acoustic density representing acoustic hysteresis, are considered as indicators of relaxation processes, equilibrium parameters of a flow, and kinds of wave exciters. Some flows with deviation from adiabaticity are examined: the Newtonian flow of a thermocon- ducting gas, the flow of a gas with vibrational relaxation, the flow of liquid electrolyte with a chemical...
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Modeling of unsaturated water flow in highly heterogeneous soils.
PublikacjaTematem pracy jest modelowanie przepływu wody w gruntach nienasyconych o podwójnej porowatości, które charakteryzują się obecnością dwóch podobszarów porowatych o skontrastowanych parametrach hydraulicznych. Jako punkt wyjścia przyjęto, że w skali lokalnej przepływ w obu podobszarach jest opisany równaniem Richardsa. Przedstawiono wyprowadzenie dwóch modeli przepływu w skali makroskopowej przy użyciu metody homogenizacji asymptotycznej....
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Two-dimensional vertical Reynolds-averaged naviers-stokes equations versus one-dimensional Saint-Venant model for rapidly varied open channel water flow modelling
PublikacjaPrzedstawiono dwa modele przepływu wody ze swobodną powierzchnią -płaski pionowy model Reynoldsa i model de Saint-Venanta.Do rozwiązania równań pierwszego modelu zastosowano schemat SIMPLE oraz wykorzystano metodę cząstek znaczonych MAC do wyznaczania swobodnej powierzchni wody. Równania Saint-Venanta rozwiązano metodą objętości skończonych. Obydwa modele zastosowano do symulacj zjawiska typu katastrofa zapory. Porównano wyniki...
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Selected aspects of two-phase flow studies using different visualization techniques in minichannels
PublikacjaThe subject of the study is to present the possibility of the use of visualization techniques in the researches on two-phase flows, carried out by the authors for many years. These works included as follows: heat transfer during the flow boiling, boiling crises and condensation in flow. The issue of the heat transfer intensification during the flow boiling through the channels of small diameters was analyzed. All this work focused...
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Two-dimensional gas chromatography – principles and application in fruits analysis
PublikacjaTwo-dimensional gas chromatography is a rapidly developing analytical technique. One of the major uses of this technique is its use for food analysis. The paper presents the principle of operation and history of this analytical technique. The specification of the two-dimensional gas chromatography technique has been discussed. The principles of separation of ingredients and application of the method, particularly in the analysis...
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Computationally Effcient Solution of a 2D Diffusive Wave Equation Used for Flood Inundation Problems
PublikacjaThis paper presents a study dealing with increasing the computational efficiency in modeling floodplain inundation using a two-dimensional diffusive wave equation. To this end, the domain decomposition technique was used. The resulting one-dimensional diffusion equations were approximated in space with the modified finite element scheme, whereas time integration was carried out using the implicit two-level scheme. The proposed...
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Improved model of isothermal and incompressible fluid flow in pipelines versus the Darcy–Weisbach equation and the issue of friction factor
PublikacjaIn this article, we consider the modelling of stationary incompressible and isothermal one-dimensional fluid flow through a long pipeline. The approximation of the average pressure in the developed model by the arithmetic mean of inlet and outlet pressures leads to the known empirical Darcy–Weisbach equation. Most importantly, we also present another improved approach that is more accurate because the average pressure is estimated...
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On exact two-dimensional kinematics for the branching shells
PublikacjaWe construct the two-dimensional (2D) kinematics which is work-conjugate to the exact 2D local equilibrium conditions of the non-linear theory of branching shells. It is shown that the compatible shell displacements consist of the translation vector and rotation tensor fields defined on the regular parts of the shell base surface as well as independently on the singular surface curve modelling the shell branching. Several characteristic...
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Magdalena Gajewska prof. dr hab. inż.
OsobyMagdalena Gajewska (ur. 1.06.1968 r. w Gdańsku) ukończyła studia w 1993 roku na Wydziale Hydrotechniki Politechniki Gdańskiej. Jest adiunktem w Katedrze Technologii Wody i Ścieków na Wydziale Inżynierii Lądowej i Środowiska Politechniki Gdańskiej. Doktorat (2001) i habilitacja (2013) w dyscyplinie inżynierii środowiska. W kadencji 2016–2020 pełni funkcję prodziekana ds. nauki. Specjalizuję się w technologiach związanych z ekoinżynierią:...
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On the correspondence between two- and three-dimensional Eshelby tensors
PublikacjaWe consider both three-dimensional (3D) and two-dimensional (2D) Eshelby tensors known also as energy–momentum tensors or chemical potential tensors, which are introduced within the nonlinear elasticity and the resultant nonlinear shell theory, respectively. We demonstrate that 2D Eshelby tensor is introduced earlier directly using 2D constitutive equations of nonlinear shells and can be derived also using the throughthe-thickness...
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Determination of dryout localization using a five-equation model of annular flow for boiling in minichannels
PublikacjaDetailed studies have suggested that the critical heat flux in the form of dryout in minichannels occurs when the combined effects of entrainment, deposition, and evaporation of the film make the film flow rate go gradually and smoothly to zero. Most approaches so far used the mass balance equation for the liquid film with appropriate formulations for the rate of deposition and entrainment respectively. It must be acknowledged...
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Application of ANN and PCA to two-phase flow evaluation using radioisotopes
PublikacjaIn the two-phase flow measurements a method involving the absorption of gamma radiation can be applied among others. Analysis of the signals from the scintillation probes can be used to determine the number of flow parameters and to recognize flow structure. Three types of flow regimes as plug, bubble, and transitional plug – bubble flows were considered in this work. The article shows how features of the signals in the time and...
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Electronic conduction in (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics
PublikacjaAmorficzny materiał (Bi,Pb)4Sr3Ca3Cu4Ox wygrzewany w odpowiednich warunkach staje się nieuporządkowanym metalem i nadprzewodnikiem. Przedstawiono model mechanizmu przewodnictwa elektrycznego tych materiałów. Przeprowadzono dyskusję istniejących teorii do opisu badanych materiałów.
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Electrical conductivity of disordered (Bi,Pb)-Sr-Ca-Cu-O materials
PublikacjaAmorficzny materiał (Bi,Pb)4Sr3Ca3Cu4Ox wygrzewany w odpowiednich warunkach staje się nieuporządkowanym metalem i nadprzewodnikiem. Ma duży opór i zazwyczaj ujemny współczynnik temperaturowej zależności oporu. W pracy dyskutowane są właściwości w stanie normalnym oraz przejście do stanu nadprzewodzącego.
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Considerations about the applicability of the Reynolds equation for analyzing high-speed near field levitation phenomena
Publikacjaequation for analyzing near field levitation (NFL) phenomena. Two separate approaches were developed, experimentally verified, and applied to meet the research objective. One was based on the Reynolds equation and the other was based on general conservation equations for fluid flow solved using computational fluid dynamic (CFD). Comparing the calculation results revealed that, for certain operating conditions, differences in the...
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Simulation of unsteady flow over floodplain using the diffusive wave equation and the modified finite element method
PublikacjaWe consider solution of 2D nonlinear diffusive wave equation in a domain temporarily covered by a layer of water. A modified finite element method with triangular elements and linear shape functions is used for spatial discretization. The proposed modification refers to the procedure of spatial integration and leads to a more general algorithm involving a weighting parameter. The standard finite element method and the finite difference...
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The modelling and enhancement of water hydrodynamics: general discussion
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Implementation of the Boundary Element Method to Two-Dimensional Heat Transfer with Thermal Bridge Effects
PublikacjaThe work presents an application of the boundary element method applied to a two-dimensional conductive heat transfer. The algorithm of the method is explained and its advantages are outlined. Green's function as a fundamental solution for Poisson's equation in two dimensions was used and the direct approach was applied. The presented results concern building construction elements as typical cases of thermal bridges. Some properties...
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Numerical modeling of hydrodynamics and sediment transport—an integrated approach
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Perspectives of Fluctuation-Enhanced Gas Sensing by Two-Dimensional Materials
PublikacjaWe present the results of gas sensing using the fluctuation-enhanced sensing method in selected two-dimensional materials (2DMs). We claim that gas sensing selectivity can be improved further by considering semiconducting two-dimensional materials doped by noble metal nanoparticles. The 2DMs' structures exhibit some imperfections defined by their structure, occurring repeatedly there. These imperfections are adsorption-desorption...
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Unstructured finite-volume meshes for two-dimensional flow in variably saturated porous media
PublikacjaW pracy opisano rozwiązanie równania przepływu nienasyconego w ośrodkach porowatych z wykorzystaniem metody objętości skończonych. Przedstawiono różne sposoby tworzenia siatki numerycznej. Przeprowadzono analizę wpływu sposobu uśredniania współczynnika filtracji między sąsiednimi objętościami skończonymi na dokładność wyników.
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Hydrodynamics and heat transfer in bubbly flow in the turbulent boundarylayer
PublikacjaW pracy przedstawiono oryginalne podejście do modelowania przepływu pęcherzykowego w warstwie przyściennej i w kanale. Podejście oparte jest na sumowaniu energii dyssypacji pochodzącej od przepływu ścinającego w kanale oraz dyssypacji pochodzącej od obecności pęcherzyków. W wyniku otrzymuje się naprężenia styczne ekwiwalentnego przepływu jednofazowego. Zaproponowano własne podejście do modelowania stopnia zapełnienia opisane równaniem...
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Impact of the Artificial Strait in the Vistula Spit on the Hydrodynamics of the Vistula Lagoon (Baltic Sea)
PublikacjaIn the Vistula Lagoon, storm surges are induced by variable sea levels in the Gulf of Gdańsk and wind action. The rising of the water level in the southern part of the basin, exceeding 1.0 m above mean sea level, can be dangerous for the lowland area of Żuławy Elbląskie, causing the inundation of the polders adjacent to the lagoon. One of the potential possibilities to limit the flood risk is to decrease the water level in the...
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Relativistic two-dimensional hydrogen-like atom in a weak magnetic field
PublikacjaA two-dimensional (2D) hydrogen-like atom with a relativistic Dirac electron, placed in a weak, static, uniform magnetic field perpendicular to the atomic plane, is considered. Closed forms of the first- and second-order Zeeman corrections to energy levels are calculated analytically, within the framework of the Rayleigh–Schrödinger perturbation theory, for an arbitrary electronic bound state. The second-order calculations are...
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Two-phase water-air flow measurement using gamma-ray absorption technique – plug flow
Dane BadawczeThe attached datasets contains the measurement results of the air-water flow in a horizontal pipeline. Flow type: plug flow. The data shows the pulse counts of the two radiometric sets. Each of these kits consisted of a QSA Global Am-241 gamma ray source and a Tesla SKG-1 type NaI(Tl) scintillation probe. The pulses were recorded using a dedicated EC...
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Two-phase water-air flow measurement using gamma-ray absorption technique – slug flow
Dane BadawczeThe attached datasets contains the measurement results of the air-water flow in a horizontal pipeline. Flow type: slug flow. The data shows the pulse counts of the two radiometric sets. Each of these kits consisted of a QSA Global Am-241 gamma ray source and a Tesla SKG-1 type NaI(Tl) scintillation probe. The pulses were recorded using a dedicated EC...
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Two-phase water-air flow measurement using gamma-ray absorption technique –bubble flow
Dane BadawczeThe attached datasets contains the measurement results of the air-water flow in a horizontal pipeline. Flow type: bubble flow. The data shows the pulse counts of the two radiometric sets. Each of these kits consisted of a QSA Global Am-241 gamma ray source and a Tesla SKG-1 type NaI(Tl) scintillation probe. The pulses were recorded using a dedicated...
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Thermal ablation modeling via the bioheat equation and its numerical treatment
PublikacjaThe phenomenon of thermal ablation is described by Pennes’ bioheat equation. This model is based on Newton’s law of cooling. Many approximate methods have been considered because of the importance of this issue. We propose an implicit numerical scheme which has better stability properties than other approaches.
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A two dimensional approach for modelling of pennate muscle behaviour
PublikacjaThe purpose of this study was to elaborate a two-dimensional approach for unipennate and bipennate striated skeletal muscle modelling. Behavior of chosen flat pennate muscle is modelled as a rheological system composed of serially linked passive and active fragments having different mechanical properties. Each fragment is composed of three elements: mass element, elastic element and viscous element. Each active fragment furthermore...
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Superconducting transition in granular Bi-Sr-Ca-Cu-O superconductors
PublikacjaW układzie(Bi,Pb)-Sr-Ca-Cu-O poprzez krystalizację w fazie stałej można wytworzyć materiały o bardzo różnych właściwościach elektrycznych i nadprzewodzących. W zależności od warunków krystalizacji, można wytworzyć nadprzewodnik o temperaturze krytycznej między 8 a 105 st. K lub materiał nie przechodzący do stanu nadprzewodzącego. Przejście do stanu nadprzewodzacego w materiałach granulastych ma charakter dwustopniowy. Zbadano wpływ...
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Flow Boiling in Minigap in the Reversed Two-Phase Thermosiphon Loop
PublikacjaThe paper presents the results of experimental investigations of a model of a heat exchanger featuring a minigap, which is perceived as an evaporator for an inverted thermosiphon. The system works with a single component test fluid. The tested evaporator generates pumping power in the test loop in a way similar to the mammoth pump. The tests regarded a module of the heat exchanger, consisting of a hot leg and a cold leg with the...
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KOLMOGOROV EQUATION SOLUTION: MULTIPLE SCATTERING EXPANSION AND PHOTON STATISTICS EVOLUTION MODELING
PublikacjaWe consider a formulation of the Cauchy problem for the Kolmogorov equation which corresponds to a localized source of particles to be scattered by a medium with a given scattering amplitude density. The multiple scattering amplitudes are introduced and the corresponding series solution of the equation is constructed. We investigate the integral representation for the first series terms, its estimations and values of the photon...
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Microwave absorption study on (Bi, Pb)-Sr-Ca-Cu-O granular superconductors
PublikacjaNadprzewodniki granulaste są bardzo ciekawymi materiałami dzięki temu, że zawierają dużą ilość złącz Josephsona. W pracy przedstawiono absorpcję mikrofalową w granulastych nadprzewodnikach (Bi, Pb)-Sr-Ca-Cu-O zawierających granule 2201, 2212 i 2223 umieszczone w matrycy dielektrycznej. Obserwowano dwustopniowe przejście do stanu nadprzewodzącego. Sygnał MMMA obserwowano poniżej temperatury T1.
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Modeling lubricant flow between thrust-bearing pads
PublikacjaInlet temperature is one of the main inputs in all models for the analysis of fluid film bearing performance. At the same time, inlettemperature distribution and also oil velocity distribution at the inlet are the result of flow phenomena in the gap between the bearingpads. These phenomena are complex and in many cases further affected by any special arrangements of forced oil supply to the gapbetween pads. The reason for such...
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Modeling of unsaturated water flow in double-porosity soils by the homogenization approach.
PublikacjaGrunty o podwójnej porowatości zbudowane są z dwóch materiałów o znacznie różniących się parametrach hydraulicznych. Ze względu na tą szczególną strukturę, podczas przepływu nieustalonego w tego typu gruntach wytwarzają się lokalne różnice ciśnienia kapilarnego. W artykule przedstawiono model przepływu w gruntach o podwójnej porowatości w skali makroskopowej z uwzględnieniem efektów lokalnych. Model otrzymano metodą homogenizacji....
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Journal of Applied Structural Equation Modeling
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Structural Equation Modeling: A Multidisciplinary Journal
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Interaction Between Storm Water Conduit Flow and Overland Flow for Numerical Modelling of Urban Area Inundation
PublikacjaNowadays we can observe increasing frequency of inundations in cities. This makes accurate predicting of inundations more important than ever. Numerical modeling of this issue requires complex approach with simultaneous calculations of pipe flow and surface flow. In this paper, after a short review of known methods used for solving pipe and surface flow, we will try to answer the question if presented methods would be sufficiently...
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Two-dimensional hydrogen-like atom in a weak magnetic field
PublikacjaWe consider a non-relativistic two-dimensional (2D) hydrogen-like atom in a weak, static, uniform magnetic field perpendicular to the atomic plane. Within the framework of the Rayleigh-Schr¨odinger perturbation theory, using the Sturmian expansion of the generalized radial Coulomb Green function, we derive explicit analytical expressions for corrections to an arbitrary planar hydrogenic bound-state energy level, up to the fourth...
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Grzegorz Boczkaj dr hab. inż.
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Modeling of entrained flow steam gasification of sewage sludge
PublikacjaProper management of sewage sludge becomes increasingly problematic due to legal requirements aiming at diminishing environmental impact, as well as rationalizing the utilization from the point of view of logistics. Steam gasification of sewage sludge can result in very good quality of the producer gas. So far, the works have been focused on the gasification in fixed bed gasifiers. However, this does not allow to take full advantage...
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Knowledge Flows in Cluster Organizations
PublikacjaThis paper aims to identify knowledge flows in cluster organizations (COs). On the basis of a literature analysis on knowledge flows and cluster organizations, the following research question was formulated: What kind of knowledge flows can be identified in cluster organizations and what is their main characteristics? The paper is based on a literature analysis and Grounded Theory methodology, examining four purposefully selected...
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Measurements of Dispersed Phase Velocity in Two-Phase Flows in Pipelines Using Gamma-Absorption Technique and Phase of the Cross-Spectral Density Function
PublikacjaThis paper concerns the application of the gamma radiation absorption method in the measurements of dispersed phase velocity in two-phase flows: liquid–gas flow in a horizontal pipe- line and liquid–solid particles in a vertical pipe. Radiometric sets containing two linear 241Am gamma radiation sources and two NaI(Tl) scintillation detectors were used in the research. Due to the stochastic nature of the signals obtained from the...
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Dariusz Mikielewicz prof. dr hab. inż.
OsobyDariusz Mikielewicz – urodził się 6 lutego 1967 roku w Gdańsku, w 1985r. zdał pomyślnie egzaminy wstępne na Wydział Budowy Maszyn Politechniki Gdańskiej, który ukończył z wynikiem bardzo dobrym w 1990 roku na specjalności Maszyny i Urządzenia Energetyczne. Zainteresowania pracą naukową skłoniły go do podjęcia badań na University of Manchester na wydziale mechanicznym i energetyki jądrowej (Mechanical and Nuclear Engineering Department)...
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Two-phase water-air flow measurement using gamma-ray absorption technique – transitional plug – bubble flow
Dane BadawczeThe attached datasets contains the measurement results of the air-water flow in a horizontal pipeline. Flow type: transitional plug – bubble flow. The data shows the pulse counts of the two radiometric sets. Each of these kits consisted of a QSA Global Am-241 gamma ray source and a Tesla SKG-1 type NaI(Tl) scintillation probe. The pulses were recorded...
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Identification of Parameters Influencing the Accuracy of the Solution of the Nonlinear Muskingum Equation
PublikacjaTwo nonlinear versions of the Muskingum equation are considered. The difference between both equations relates to the exponent parameter. In the first version, commonly used in hydrology, this parameter is considered as free, while in the second version, it takes a value resulting from the kinematic wave theory. Consequently, the first version of the equation is dimensionally inconsistent, whereas the proposed second one is consistent. It...
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Non-adiabatic Effects in Pressure Drop Calculations in Flow Boiling and Flow Condensation in Minichannels
PublikacjaConsiderations presented in the paper relate both to the case of flow boiling and flow condensation in conventional channels as well as small diameter ones. Authors devoted all the possible attention that the modeling presented is applicable to the whole range of quality variation in both cases of condensation and boiling. The form of two-phase flow multiplier, which is a major factor in modeling presented here, should be capable...
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Investigations On Water Circulation in Animal Sea-Water Basins – On the Example of Seals′ Breeding Pools
PublikacjaThis paper presents general comments concerning investigations on water circulation in animal breeding pools containing sea water. As an example are given results of computer simulation of water circulation in seals’ breeding pools situated in Marine Station at Hel, belonging to Oceanographic Institute, Gdansk University. A mathematical model of three main pools was prepared with taking into account their inflow and outflow water...
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Problems of Measuring Gas Content in Oil in a Two-Phase Flow: A Review
PublikacjaIn view of the necessity of measuring the air content in oil in two-phase flows in the context of general industry, a review of the most popular methods of measuring the air content in oil was carried out. This review includes an assessment of their advantages and disadvantages and of whether they meet criteria such as the degree of filling, the size and number of bubbles, verification, the absence of additional pressure drops,...