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EN
A bulbous bow is a typical ship structure. Due to the influence of the bulbous bow, complex flow separation and gas capture phenomena may appear during the water entry of ship-like sections. In this paper, experimental and numerical studies on the water entry of a ship-like section with an obvious bulbous bow are carried out. Two thin plates are installed at both ends of the test model to ensure that the flow field during the impact process is approximately twodimensional. The free-fall drop test is carried out in the test rig equipped with guide rails. By changing drop heights, impact pressure on the model surface with different initial impact velocities is measured. A numerical model for simulating the water entry of the ship-like section is established by using the Computational Fluid Dynamics (CFD) method, based on the Navier-Stokes equations. Reasonable time steps and mesh size are determined by convergence analysis. Four different flow models are used in the numerical analysis. It is found that the K-Epsilon turbulence model can present the most reasonable numerical prediction by comparing numerical results with the experimental data. Furthermore, the influence of the bulbous bow on the impact loads is numerically studied by using the validated numerical model. It suggests that the bulbous bow has little effect on the impact force acting on the bow-flared area but, in the position near the bulbous bow, the pressure will be affected by the second slamming and the air cushion.
2
Content available remote Modelling of heat transfer in a packed bed column
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EN
The CFD modelling of heat transfer in the packed bed column in the laminar and turbulent flow regimes has been presented. Three numerical grids with different densities were generated for the packed bed column. The modelling was performed with the use of the Porous Media Model for treating the flow inside a porous structure. The standard k-ε model along with the logarithmic wall functions for the turbulent flow range was used. The influence of the mesh size on the accuracy of the fluid flow was studied. Both radial and axial direction temperature distributions have been compared with the experimental data1 and the values calculated from a 2DADPF model. A good agreement between the experimental and the predicted values of the pressure drop, temperature distributions and heat transfer coefficient was obtained.
EN
The CFD modelling of heat transfer in a microtubular Solid Oxide Fuel Cell (mSOFC) stack has been presented. Stack performance predictions were based on a 16 anode-supported microtubular SOFCs sub-stack, which is a component of the overall stack containing 64 fuel cells. Both radiative and convective heat transfer were taken into account in the modelling. The heat flux value corresponded to the cell voltage of 0.7 [V]. Two different cases of the inlet air velocity of 2.0 and 8.5 [ms–1] were considered. It was found that radiation accounted for about 20–30 [%] of the total heat flux from the active tube surface, which means that the convective heat transfer predominated over the radiative one.
PL
W pracy przeprowadzono badania numeryczne streamingu akustycznego, wywołanego ścianą drgającą z częstotliwością 20 kHz oraz 40 kHz w kanale o przekroju prostokątnym. Częstotliwość oscylacji ściany dostosowano do długości kanału tak, aby wytworzyć sinusoidalną falę stojącą. Uśredniono przepływ w kanale i pokazano strukturę przepływu będącego streamingiem akustycznym. Dodatkowo wprowadzono różnicę temperatur między górną i dolną ścianą kanału. Pokazano, że streaming akustyczny intensyfikuje wymianę ciepła między ścianami kanału oraz że jego intensywność zwiększa się wraz z różnicą temperatury między ścianami. Wskazano również na potencjalne wykorzystanie badanego zjawiska do chłodzenia elektroniki w warunkach braku grawitacji (braku konwekcji naturalnej).
EN
The paper presents a modelling procedure of the M-28 Bryza wing with extended flaps and Computational Fluid Dynamics (CFD) simulations results preformed in order to assess the performance of the investigated wing for various flap extension rates. The M-28 Bryza is a two-engine high-wing aircraft used in the Polish Air Force for short distance airlift of people and equipment. The aim of this work was to determine the aerodynamic characteristics of the investigated wing. The CFD simulations were performed in order to investigate the influence of flap extension on lift and drag coefficients at various angles of attack. In order to validate the results of two different commercial CFD packages were used. The findings are presented in the form of flow visualization and aerodynamic characteristics. The typical and non-standard extension rates were investigated for low, moderate and high angles of attack. The results correlated with the limitations specified in the aircraft manual. The outcome of the presented work confirmed the feasibility of the presented methodology for its use as a supportive tool for providing additional information about airplane performance in standard and non-standard conditions of flight such as landing with one engine working. The results of work might prove useful for M-28 Bryza pilots and maintenance personnel as well as for educational purposes.
EN
The hydraulic performance of constructed wetlands is often compromised by hydraulic problems. Therefore, the development of an appropriate simulation model to reliably predict how various modifications of bed design and configurations might affect performance will facilitate the design of efficient systems. The aim of this research work is to determine distribution of residence time in a field-scale horizontal subsurface flow constructed wetland with Palm Kernel Shell as substrate. The governing equations of flow in porous media and transport of diluted species were solved using COMSOL Multiphysics 5.3a. The result was validated using experimental data and the model result showed good agreement with a correlation coefficient of 0.99. Alternative wetland designs were assessed for the same flow conditions. The results revealed that a two cell wetland improved short-circuiting flow paths.
EN
A novel three products hydrocyclone screen (TPHS) has been successfully developed; it consists of a cylindrical screen embedded in a conventional hydrocyclone (CH). In the new liquid cyclone, the combination of centrifugal classification and screening was employed for particle separation based on size. The aim of this study is to investigate the flow behaviour in TPHS using numerical simulation and experimental validation. A computational fluid dynamics simulation with a 4.35 million grid scheme and linear pressure–strain RSM generated the economic and grid-independence solution, which agreed well with the experiments of particle image velocimetry and water split. The velocity vector profile reveals that TPHS represented similar flow patterns to CH, wherein in addition to the outer downward swirl flow, inner upward swirl flow, central down-flow, second circulatory flow, and mantle, a particular fluid flow named screen underflow was created in TPHS owing to the presence of a cylindrical screen. The velocity distribution demonstrates that in TPHS, relative to CH, with the increase in radius, the lower tangential and higher radial velocity first increased to a peak and subsequently decreased, while the axial velocity primarily reduced to zero, increased in the opposite direction, and finally decreased rapidly to zero again. In addition, a disadvantageous flow, namely, screen backflow, was generated in TPHS, wherein the farther away the flow is from the feed inlet, the earlier this flow behaviour occurred. However, the rational scheme of aperture size and screen length can completely remove the screen backflow in TPHS.
EN
The article presents the results of a computational fluid dynamics (CFD) analysis of gas-liquid multiphase flow. The simulation was conducted using CFD code and the Euler–Euler approach. The presented study relates to the non–reactive, steady-state, turbulent flow of water and carbon dioxide mixture in a 3D pipe. Separation phenomenon between phases is observed. The solution was obtained using a mixture model. Different values of carbon dioxide volume fraction were taken into account in the analysis of the results. The analysed cases were compared thanks to the obtained calculations results. The main purpose of the simulations was to show streamlines, velocity, pressure, and volume fraction distribution that could be useful in developing pipeline systems in many industrial applications, especially for CO2 separators.
11
Content available remote Cfd Analysis of Heat Transfer in a Microtubular Solid Oxide Fuel Cell Stack
88%
EN
The aim of this work was to achieve a deeper understanding of the heat transfer in a microtubular Solid Oxide Fuel Cell (mSOFC) stack based on the results obtained by means of a Computational Fluid Dynamics tool. Stack performance predictions were based on simulations for a 16 anodesupported mSOFCs sub-stack, which was a component of the overall stack containing 64 fuel cells. The emphasis of the paper was put on steady-state modelling, which enabled identification of heat transfer between the fuel cells and air flow cooling the stack and estimation of the influence of stack heat losses. Analysis of processes for different heat losses and the impact of the mSOFC reaction heat flux profile on the temperature distribution in the mSOFC stack were carried out. Both radiative and convective heat transfer were taken into account in the analysis. Two different levels of the inlet air velocity and three different values of the heat losses were considered. Good agreement of the CFD model results with experimental data allowed to predict the operation trends, which will be a reliable tool for optimisation of the working setup and ensure sufficient cooling of the mSOFC stack.
EN
The present study deals with modelling and validation of a planar Solid Oxide Fuel Cell (SOFC) design fuelled by gas mixture of partially pre-reformed methane. A 3D model was developed using the ANSYS Fluent Computational Fluid Dynamics (CFD) tool that was supported by an additional Fuel Cell Tools module. The governing equations for momentum, heat, gas species, ion and electron transport were implemented and coupled to kinetics describing the electrochemical and reforming reactions. In the model, the Water Gas Shift reaction in a porous anode layer was included. Electrochemical oxidation of hydrogen and carbon monoxide fuels were both considered. The developed model enabled to predict the distributions of temperature, current density and gas flow in the fuel cell.
EN
The aim of this paper was to demonstrate the feasibility of using a Computational Fluid Dynamics tool for the design of a novel Proton Exchange Membrane Fuel Cell and to investigate the performance of serpentine micro-channel flow fields. A three-dimensional steady state model consisting of momentum, heat, species and charge conservation equations in combination with electrochemical equations has been developed. The design of the PEMFC involved electrolyte membrane, anode and cathode catalyst layers, anode and cathode gas diffusion layers, two collectors and serpentine micro-channels of air and fuel. The distributions of mass fraction, temperature, pressure drop and gas flows through the PEMFC were studied. The current density was predicted in a wide scope of voltage. The current density – voltage curve and power characteristic of the analysed PEMFC design were obtained. A validation study showed that the developed model was able to assess the PEMFC performance.
EN
With the constant growth of computer simulation significance in science and engineering, many new fields are gaining access to these powerful tools. One of these new disciplines is medicine. Human body provides many fascinating areas that could be researched from completely different angle and could gain all the benefits that computer simulation offers. For example blood flow in human arteries can be studied using Computational Fluid Dynamics. Researchers of cerebrovascular disorders can get an insight view on physical phenomena of blood flow and study risk factors of embolism or cerebral aneurysm. Main issue in using computer simulation in medical research is the complexity and uniqueness of geometry that needs to be handled. After all, human body is one of the most sophisticated engineering systems created by nature. In this paper, a workflow for creating a numerical mesh for CFD simulation purposes is shown. Application shown in the example focus on cerebral arteries blood flow simulation. Numerical mesh is generated based on CT scan of patient’s head, using freeware tools Slicer3D and AutoIt3 as well as commercial software ANSYS Fluent Meshing 15.0.
EN
This paper presents modelling of a three way flow control valve by the use of CFD tool. FSI unit in simulation of interaction between flowing fluid and movable valve components has been used. Selected results (velocity and pressure distribution as well as flow rate on inlet and receiver port) for step increase of pressure at valve inlet and on pressure changes at receiver port have been presented.
PL
Przedstawiono modelowanie trójdrogowego regulatora przepływu i wykorzystanie narzędzi numerycznej analizy zjawisk przepływowych CFD (Computational Fluid Dynamics). Zaprezentowano wybrane wyniki analizy CFD-FSI dla przykładowych warunków pracy podczas skokowego przyrostu ciśnienia w linii zasilania regulatora i przy zmianie ciśnienia w przyłączu odbiornika.
EN
Every change in the bottle geometry as well as every change of physical and rheological properties posesa risk of excessive gas entrainment during a filling process. To maintain satisfactory filling efficiencythere is a need to optimise this process with respect to all adverse phenomena which affect the fluidflow, such as spluttering on the bottom, air caverns formation and air entrainment with incoming liquid.This paper comprises numerical simulations of two filling methods. The first method involves dosingwith a pipe placed over the free liquid surface of a fully filled bottle. The second method covers fillingwith a pipe located near the bottom. Moreover, the influence of rheological properties and surfacetension values is considered. The comprehensive analysis of amount of entrained air represented byair volume fraction in dispensed liquid let the authors define the influence of filling speed on themechanism and amount of entrapped air.
PL
W artykule przedstawiono wyniki symulacji modelu składającego się odcinka rurociągu, w którym płynie gaz ziemny pod ciśnieniem, a ruch płynu zakłócony jest elementem pomiarowym typu annubar. Celem jest wykazanie czy przepływ gazu ziemnego pod wysokim ciśnieniem może uszkodzić element wykonawczy przepływomierza. Dzięki zastosowaniu komputerowej mechaniki płynów (ang. Computational Fluid Dynamics) zasymulowany został realny przepływ gazu ziemnego przez rurę z elementem pomiarowym. Uzyskane wyniki pozwalają wnioskować, że przepływ gazu może powodować uszkodzenie elementu pomiarowego wskutek powstania zmiennej w czasie reakcji aerodynamicznej. Dzięki wynikom symulacji zaproponowane zostało wstępne rozwiązanie problemu. Rozwiązanie rozważanego problemu jest istotne, ponieważ może przyczynić się do osiągnięcia większej niezawodności elementów pomiarowych.
EN
The article presents the results of a model simulation comprising a pipeline section with natural gas flowing under pressure, and the fluid movement is disrupted with a measurement element of annubar type. The goal is to determine whether the flow of gas under high pressure can damage the operating element of a flowmeter. Thanks to the use of CFD (Computational Fluid Dynamics), the real flow of natural gas through a pipeline with a measurement element was simulated. The results obtained make it possible to claim that the flow of gas can damage the operating element due to an aerodynamic reaction variable in time. As a result of the simulation, a preliminary solution has been suggested. The solution of the problem is important, since it can lead to obtaining greater reliability of measurement elements.
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