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EN
Reducing friction with specialised hull coatings or air lubrication technologies has a potential reducing energy consumption and emissions in shipping. The EU project AIRCOAT combines both by developing a passive air lubrication technology inspired by nature that is implemented on a self-adhesive foil system. Besides validating the friction reduction it is of high interest to understand the underlying mechanism that causes the reduction. Therefore, a flow channel was designed, that creates a stationary turbulent flow within a square duct allowing for non-invasive measurements by laser doppler velocimetry. The high spatial resolution of the laser device makes recording velocity profiles within the boundary layer down to the viscous sublayer possible. Determination of the wall shear stress τ enables direct comparison of different friction reduction experiments. In this paper we validate the methodology by determining the velocity profile of the flat channel wall (without coatings). We further use the results to validate a CFD model in created in OpenFOAM. We find that velocities along the longitudinal axis are generally in good agreement between numerical and experimental investigations.
EN
Energy efficiency has become more important in every industry and daily life. Designing and building a more efficient marine vehicle can lead to lower fuel consumption and a longer lifetime for the components of the vehicle. Erosion caused by cavitation reduces the service life of the propeller and the related components in the propulsion and maneuvering system. Reducing cavitation leads to a longer life for these components. This paper aims to explain and investigate propeller blade cup as a cavitation reduction method for marine propellers. A cavitating no-cup propeller is created and analyzed then the cupped version of this propeller is generated and analyzed to compare with the no-cup propeller. Cavitation results of these propellers are investigated. In addition, the thrust, torque, and efficiency of the propellers are compared.
3
Content available remote Modelowanie wpływu warunków środowiska pożarowego na dostępny czas ewakuacji
PL
W artykule przedstawiono analizę numeryczną wpływu czynników towarzyszących występowaniu pożaru na dostępny czas ewakuacji, na podstawie przyjętego scenariusza pożarowego w wybranym pomieszczeniu. Środowisko pożaru modelowano za pomocą zaawansowanych metod numerycznych CFD w programie FDS. Na podstawie wartości krytycznej zasięgu widzialności określony został czas, po którym użytkownicy nie byli w stanie ewakuować się z analizowanego pomieszczenia objętego pożarem w sposób bezpieczny dla ich zdrowia i życia. Dokonano oceny potencjału aplikacyjnego oprogramowania FDS do przeprowadzenia analiz związanych z wpływem warunków pożaru na dostępny czas ewakuacji w obiekcie.
EN
In the article a numerical analysis of the influence of factors accompanying the occurrence of fire for the available evacuation time was presented, based on the adopted fire scenario in a selected room. The fire environment modeling was performed using advanced numerical methods CFD in the FDS software. On the basis of the critical value of the visibility range, the time after which the users were not able to evacuate from the analyzed room under fire in a safe manner for their health and life was determined. The application potential of the FDS software was assessed for carrying out analyzes related to the impact of fire conditions on the available evacuation time in the facility.
EN
Wind towers are passive architectural elements traditionally used to ventilate buildings in the Middle East’s hot and arid regions. Some recent design initiatives in Jordan are particularly interested in using passive systems for natural ventilation. This paper focuses on an innovative wind tower design as a passive ventilation system, which will be integrated into a train station design in Aqaba, Jordan to improve the air quality in indoor spaces and reduce the cooling loads. The design uses wind-induced effects as the motivating forces to improve natural ventilation. The study optimized the wind tower and evaluated its performance using Autodesk Computational Fluid Dynamics (CFD) simulations and Grasshopper Rhino plug-ins. Airflow and distribution through the tower were analyzed using the CFD model. Grasshopper definitions were used to examine the tower efficiency in lowering the indoor air temperature. Simulations indicated the potential of the proposed wind tower to reduce the temperature by 6.164°C and supply the interior space with the required fresh air rates. This article outlines how wind towers can be used in contemporary architecture and incorporate the simulation methods to pave the way for architects to effectively validate the performance of their design proposals at the early design stage.
EN
Cell manipulation using external magnetic fields has been proposed to accelerate the neck reendothelization of saccular unruptured stented intracranial aneurysms. This work presents a computational fluid dynamics (CFD) model of a Saccular Brain Aneurysm that incorporates a helicoidal stent. An Eulerian-Lagrangian model implemented in ANSYS-Fluent is used to simulate the hemodynamics in the aneurysm. In silico studies have been conducted to describe the incidence of the magnetic field direction, frequency and amplitude on the blood hemodynamics and particle capture efficiency, when an external magnetic field is used to trap magnetically labeled particles traveling through the aneurysm. It is found that the magnetic field direction affects the particle concentration in the target region. Simulation results show that the highest particle capture efficiency is obtained with a 1T magnetic field amplitude in an open bore MRI scanner, when a permanent magnet is used.
EN
Along with the increase in computing power, new possibilities for the use of parametriccoupled analysis of fluid flow machines and metamodeling for many branches of industryand medicine have appeared. In this paper, the use of a new methodology for multi-objective optimization of a butterfly valve with the application of the fluid-structure interaction metamodel is presented. The optimization objective functions were to increasethe value of the KV valve’s flow coefficient while reducing the disk mass. Moreover, theequivalent von Mises stress was accepted as an additional constraint. The centred composite designs were used to plan the measuring point. Full second-order polynomials, non-parametric regression, Kriging metamodeling techniques were implemented. The optimization process was carried out using the multi-objectives genetic algorithm. For eachmetamodel, one of the optimization candidates was selected to verify its results. The besteffect was obtained using the Kriging method. Optimization allowed to improve the KVvalue by 37.6%. The metamodeling process allows for the coupled analysis of the fluidflow machines in a shorter time, although its main application is geometry optimization.
7
Content available remote Computational fluid dynamics and experimental hydrodynamic analysis of a solar AUV
EN
In the present study, the effect of free surface on the hydrodynamic forces acting on themotion of an autonomous underwater vehicle (AUV) has been investigated. The AUVis powered by solar energy. Using computational fluid dynamics, the Reynolds averaged Navier Stokes (RANS) equations for the flow around the AUV are solved, and the freesurface effect is simulated using the volume of fluid (VOF) two-phase flow model. Forthis purpose, the commercial code ANSYS FLUENT 18 was used [1]. The results ofthe numerical solution are compared with experimental results of the AUV model in thesurface motion in the towing tank of the Persian Gulf National Laboratory with a scaleof 1:1. The experiment was performed in a fixed draft and the velocity was ranging from 0.2 m/s to 1.4 m/s (according to Reynolds number 2.4 x 105 to 1.7 x 106).
EN
Tortuosity in coronary artery has been found to be greatly related to the potential sites of stenosis in these last years. Many investigations have been carried out based on the tool of Computational Fluid Dynamics (CFD) mainly focusing on the influences of curved artery in blood flow. Within the limited investigations of coupling between stenosis and tortuosity, the stenosis has been considered to be located at the tortuous segment. However, with recent clinical studies, the case of stenosis occurred at non-tortuous segment before tortuosities has been confirmed which has not been paid enough attention yet. Therefore, the present study aims to investigate the disturbed streamlines and hemodynamics in curved and spiral artery considering symmetrical and asymmetrical stenosis upstream these tortuosities. Different stenosis severities, pulse rates and distances between stenosis and tortuosity as controlling parameters have been studied. The distribution of time averaged wall shear stress (TAWSS) and streamlines through tortuous segment have been displayed in order to determine the potential disease sites. Artery surface of TAWSS below critical value has been quantified as well to evaluate the risks of atherosclerosis. The results reveal that larger artery surface of TAWSS below critical value generally goes with smaller pulse rate, larger stenosis severity and distance between stenosis and tortuosity both for curved and spiral artery. However, exceptions were found in the cases of distance of 6 mm in curved artery with symmetrical stenosis and stenosis severity of 50% in spiral artery. Moreover, the spiral tortuosity tends to suppress the potential risks of atherosclerosis compared to curved tortuosity.
EN
Computational fluid dynamics (CFD) has progressed rapidly in the past fifty years and is now used in many industrial fields, such as air, space, and marine engineering. CFD has an irreplaceable role in marine design and scientific research, and its applications within this field continue to grow with the development of computers. CFD is used to quickly and inexpensively simulate fluid behaviour using the Reynolds Averaged Navier–Stokes (RANS) equations to calculate hydrodynamic coefficients, which are needed in manoeuvrability studies of underwater vehicles (UWV). Here, these computations are performed for six geometrical shapes that represent typical autonomous underwater vehicles (AUVs) currently in use. Resistance test simulations at up to 20o drift angles were conducted for AUVs with different length-to-diameter ratios. The results were compared with the experimental data and current quasi-experimental relationships, which suggested that the CFD predictions were adequately precise and accurate. These predictions indicated that there was a non-linear relationship between forces and moments and the lateral speed. Moreover, both linear and non-linear hydrodynamic coefficients were calculated.
10
Content available remote Numerical studies of internal flow in different types of filters
EN
The quality of ambient air attracts considerable, widespread interest. Over the last decades, air purification has become an integral part of HVAC systems, process engineering, automotive and respiratory protection. Efficient separation of micro- and nano- particles is solidly linked with the development of new, sophisticated filtrating materials, as well as generating and validating mathematical models of such porous structures. The paper regards the numerical modeling of various filters. The presented work aims to validate four virtual filtrating materials – the fiberglass HEPA filter, the paper filter used in the automotive industry, knitted wire mesh and polyurethane foam. The pressure drop obtained for the filters under investigation was examined. The CFD results were validated against the data available in the literature. The agreement of the results of numerical and experimental studies proves the suitability of the proposed methods. At the same time, the simplifications employed in the simulations leave room for further improvement in future works.
PL
Zjawiska lewitacji stanowią potencjalnie interesującą alternatywę dla wielu rozwiązań tradycyjnych i są przedmiotem szerokich badań. Istota lewitacji polega na równoważeniu siły grawitacji innym oddziaływaniem, np. magnetycznym. Jako przykład praktycznego wykorzystania tego fenomenu można wymienić chociażby łożyska wykorzystujące zjawisko lewitacji magnetycznej. Inną metodą uzyskania efektu lewitacji jest oddziaływanie falą akustyczną. Powstająca w tym przypadku siła nośna wywołana jest niezerową wypadkową sumarycznego ciśnienia wywołanego oddziaływaniem fali akustycznej na powierzchni lewitującego ciała. W pracy omówiono podstawy fizyczne zjawiska lewitacji akustycznej oraz potencjalny obszar jego zastosowań w energetyce. Przedstawiono również wstępne wyniki badań modelowych, obejmujących wyznaczenie wpływu podstawowych parametrów środowiskowych, w tym względnego położenia lewitującego ciała, częstotliwości fali akustycznej oraz wilgotności gazu roboczego, na wartości charakterystycznych parametrów zjawiska, w tym maksymalnej siły nośnej. Otrzymane wyniki wskazują na możliwość wykorzystania zjawiska przy zmiennych właściwościach fizycznych gazu roboczego, pod warunkiem ograniczenia masy lewitującej drobiny. Rezultaty wykazują jednocześnie graniczne wartości parametrów środowiskowych, które można uznać za akceptowalne w przypadku wykorzystania omawianego fenomenu. Zebrane dane uwidaczniają fundamentalną zależność siły nośnej od położenia lewitującej drobiny w kanale akustycznym oraz częstotliwości fali akustycznej. Wyniki badań prezentują także ograniczony wpływ wilgotności gazu na parametry zjawiska.
EN
Since the levitation phenomena are potentially interesting alternative to many traditional solutions, they state currently a subject of extensive research. The principle of the levitation consists in balancing the force of gravity with another interaction, e.g. magnetic. As an example of the use of this phenomenon, the bearings using the phenomenon of magnetic levitation might be mentioned. Another method of obtaining the effect of levitation is acoustic wave interaction. The lift force generated in this case is caused by a non-zero resultant vector of the total pressure caused by the impact of the acoustic wave on the surface of the levitating body. The paper discusses the physical foundations of the phenomenon of acoustic levitation and the potential area of its applications in energy. Preliminary results of model tests, including determination of the impact of basic environmental parameters, including the relative position of the levitating body, frequency of the wave and humidity of the gas, on the values of the characteristic parameters of the phenomenon, including the maximum lift are presented. The obtained results indicate the possibility of using the phenomenon with variable physical properties of the working gas, provided limited the mass of levitat-ing particles. Simultaneously, the results show the limit values of environmental parameters that can be considered acceptable when the phenomenon in question is used. The collected data show the fundamental dependence of the lift force on the position of levitating particles in the acoustic channel and the frequency of the acoustic wave. The test results also present a limited effect of gas humidity.
EN
Nuclear power plants play an important role in power systems of many countries. Ability to reasonable increase installed capacity of nuclear power units allow to reduce the cost for building of new power plants. When increasing NPP capacity to 104% there is a need to estimate the residual life of plant’s typical elements and continue their operation. The mathematical model of estimation of service life indicators of steam turbine K-1000-60/3000 is developed. The effect of increasing the capacity of a nuclear reactor on the heat transfer coefficients of a steam in the nozzle segments of high-pressure cylinder was established by using CFD modeling. The thermal and stress-strain state of the high-pressure rotor for the most typical operating modes are calculated. Using the correlation dependences of low-cycle fatigue, the rate of accumulation of cyclic damage of the base metal is established. The resistance of the metal to the exhaustion of long-term strength is also determined. On the example of the high pressure rotor of the 3rd power unit of Rivne NPP the service life indicators are calculated. The validity of increasing the installed capacity of the power unit was also confirmed.
EN
The cyclonic-static micro-bubble flotation column (FCSMC) performs well in fine mineral flotation. Compared to traditional flotation columns, its design innovatively introduces a cyclonic structure. The separation of middling and tailing occurs in the cyclonic flow field induced by a cyclonic reversal cone. In this study, the particle size distribution analysis and computational fluid dynamics (CFD) simulations were conducted to reveal the particle distribution law and the classification mechanism in cyclonic flow fields under different circulation pressures. The results showed that particle size showed the same distribution tendency as tangential velocity in the radial direction: both increase from the center and decrease around the wall. As circulation flux increased, the tangential velocity increased, and the particle size differences in the radial direction also increased. The position of the largest particles will move to outside as the largest value of tangential velocity migrates the outward in the radial direction. According to the particle size distribution of the feed, it can be adjusted to the flow field to change the particle distribution, thereby improving the efficiency of separation. This study has an important guiding significance for column design and adjustment of the operating parameters of the flotation process.
PL
W artykule przeprowadzono analizę wpływu potencjalnych źródeł ciepła występujących w pomieszczeniu, zabezpieczanym stałym urządzeniem gaśniczym gazowym, na rozkład stężenia gazu gaśniczego, a tym samym na skuteczność gaśniczą systemu. W badaniach wykorzystano komorę badawczą wyposażoną w stałe urządzenie gaśnicze na dwutlenek węgla oraz aparaturę umożliwiającą dokonywanie pomiarów zmian stężenia gazu gaśniczego w czasie. Badania zostały wykonane w trzech wariantach: przy braku obecności źródeł ciepła; z uwzględnieniem pożaru oraz z uwzględnieniem pożaru i stałego źródła ciepła, w postaci elektrycznej płyty grzewczej, umieszczonego w komorze badawczej. Na podstawie przeprowadzonych analiz stwierdzono znikomy wpływ źródeł ciepła na rozkład stężenia gazu gaśniczego w zaproponowanym układzie przestrzeni chronionej.
EN
This article undertakes to conduct an experimental analysis of the impact of potential heat sources occurring in the room protected by FES-gaseous on the distribution of extinguishing gas concentrations, and thus on the extinguishing efficiency of the system. The research used a test chamber equipped with a fixed gaseous extinguishing system on carbon dioxide and apparatus enabling measurements of changes of extinguishing gasconcentration over time. The tests were carried out in three variants: in the absence of heat sources, with the presence of fire and taking into account the fire and a constant heat source in the form of an electric hobin the test chamber. Based on the analyzes carried out, a slight impact of the heat sources on the distribution of extinguishing gas concentrations in the proposed arrangement of protected space was found.
PL
W artykule zaprezentowano ocenę nowego podejścia do przewidywania zmian ciśnienia podczas wyładowania gazu gaśniczego do pomieszczenia chronionego stałymi urządzeniami gaśniczymi gazowymi za pomocą symulacji numerycznych CFD (ang. Computational Fluid Dynamics). Program badawczy składał się z dwóch etapów: pierwszy poświęcony był eksperymentalnym pomiarom zmiany ciśnienia podczas uwolnienia gazu gaśniczego do komory badawczej w skali rzeczywistej (70 m3) z zastosowaniem otworu odciążającego. Drugim etapem było wykonanie symulacji CFD pozwalających wyznaczyć zmiany ciśnienia podczas wyładowania gazu do reprezentowanej numerycznie komory testowej. Oszacowanie poprawności i użyteczności modelu CFD polegało na porównaniu wyników CFD ze standardowymi obliczeniami i pomiarami eksperymentalnymi.
EN
The aim of the article is to investigate and evaluate a new approach for prediction of changes of pressure during gas discharge inside the room protected by fixed gaseous extinguishing system by means of CFD simulations (ang. Computational Fluid Dynamics).The research program consisted of two stages. The first stage was dedicated to the experimental measurements of pressure changes during extinguishing gas discharge into the test chamber in a real scale (70 m3) with use of relief opening. The next step was about performing CFD simulations allowing to determine pressure changes during gas discharge into the numerically represented test chamber. Estimation of the correctness and usefulness of the CFD model was based on a comparison of the CFD results with standard calculations and experimental measurements.
16
Content available remote Analysis and optimization of radiant cooling panel with wave-type embedded pipes
EN
In this study, the radiant cooling panel with wave-type pattern pipes is analyzed and optimized through Taguchi’s design of experiments methods and grey relation method for better performance. Radiant cooling panel’s bottom surface temperature and temperature non-uniformity index are considered as the quality objective functions. Control parameters such as pipe length, the spacing between the pipes, radiant panel thickness, pipe bent radius, pipe diameter, insulation layer thickness, pipe material, panel material, insulation material, and mass flow rate of water entering the pipe are included as the control parameters of the optimization study. The performance of radiant cooling panels is analyzed through numerical simulation technique- computation fluid dynamic (CFD) method. The numerical simulation is carried out in the Fluent software, and the CFD code is checked for grid independence and validation. Through single and multi-objective optimization, the best design of the radiant cooling panel is identified, and a confirmation test is also conducted. Finally, an analysis of variance (ANOVA) calculation is made and it is found that the mass flow rate of water entering the pipe is the most influencing parameter on the performance of the radiant cooling panel.
EN
In this work a multilevel CFD analysis have been applied for the design of an engine exhaust system include manifold and muffler with improved characteristics of noise reduction and fluid dynamic response. The approaches developed and applied for the optimization process range from the 1D to fully 3D CFD simulation, exploring hybrid approaches based on the integration of a 1D model and 3D tools. Once the best configuration has been defined, the 1D-3D approach has been adopted to confirm the prediction carried out by means of the simplified approach, studying also the impact of the new configuration on the engine performances.
EN
FEM (finite element method) is an essential and powerful numerical method that can explicitly optimize the design process of electrical devices. In this paper, the employment of FEM tools such as SolidWorks, COMSOL and ANSYS is proposed in order to aid electrical apparatuses engineering and modeling – those are arc chambers of modular circuit breakers. Procured models of arc chambers have been undergoing simulations concerning heating, electric potential distribution, electric charge velocity and traverse paths. The data acquired has been juxta-positioned against experimental data procured in the Short-Circuit Laboratory, Warsaw University of Technology. The reflection of the theoretical approach was clearly noted in the experimental results. Mutual areas of the modeled element expressed the same physical properties and robustness errors when tested under specific conditions – faithfully reflecting those which were experimented with. Moreover, the physical phenomena essential for electrical engineering could be determined already at the model stage. This procedure proved highly valuable during designing/engineering work in terms of material economy.
19
Content available remote Impact of coronary tortuosity on the artery hemodynamics
EN
The presence of tortuosity in coronary artery (CA) affects the local wall shear stress (WSS) which is an influencing hemodynamic descriptor (HD) for the development of atherosclerotic sites. To conduct a morphological parametric study in coronary arteries (CAs), several idealized tortuous artery models were obtained by varying three morphological indices namely, curvature radius (CR), distance between two bends (DBB) and the angle of bend (AoB). Computational fluid dynamics methodology with multiphase mixture theory is used to explore the effect of coronary tortuosity on various WSS based hemodynamic descriptors (HDs) namely, time-averaged WSS, oscillatory shear index, time-averaged WSS gradient, endothelial cell activation potential and the relative residence time that are used to determine the vulnerable locations for the onset of thrombosis and atherosclerosis. Our findings suggest that all the tortuosity morphological indices, CR, DBB and AoB have significant influence on the distributions of various HDs and hemodynamics. It is also observed that atherosclerosis prone sites were witnessed at the inner artery wall at downstream regions of the bend section 1 and bend section 2 in all the tortuous artery models studied and found to increase as the CR and DBB were reduced however, found to increase as the AoB is increased. Hence, severe coronary tortuosity in CAs with small CR, small DBB and higher AoB may have lower WSS zones at inner bend sections which promote atherosclerosis plaque progression. The analysis obtained from this multiphase blood flow study can be employed potentially in the clinical assessment on the severity of atherosclerosis lesions as well as in understanding the underlying mechanisms of localization and formation of atherosclerotic plaques.
PL
Artykuł przedstawia wyniki prac nad doborem optymalnych modeli turbulencji, opisujących przepływ powietrza kopalnianego w chodnikach wykonanych w obudowie łukowej. Poszukiwany jest opis, który zapewni zadowalającą dokładność symulacji przy możliwie niskim zapotrzebowaniu na moc obliczeniową. W ramach badań ukierunkowanych na dobór modeli turbulencji kontynuowano przegląd literatury oraz badania in-situ. Opracowano rodzinę modeli numerycznych przepływu powietrza w chodniku KD Barbara, w którym zespół IMG-PAN prowadził pomiary prędkości przepływu przy pomocy termoanemometrów i metanoanemometrów. Modele te wykorzystują metodę objętości skończonej i modele turbulencji k-e, k-ωSST, SAS i GEKO. Wykonano szereg obliczeń z zastosowaniem wybranych modeli turbulencji. Przeprowadzono analizę warunków przepływowych w miejscu pomiarów. Porównano wyniki pomiarów i symulacji. Na podstawie uzyskanych wyników sformułowano plany dalszych eksperymentów in-situ.
EN
The article presents the results of work on the selection of optimal turbulence models describing the flow of mine air in airways with arched roof support. A description is sought that will ensure satisfactory simulation accuracy with the lowest possible computing power demand. As part of research aimed at selecting turbulence models, literature review and in-situ research were continued. A family of numerical models of air flow in the KD Barbara gallery, in which the IMG-PAN team carried out measurements of flow velocity using thermoanemometers and metanoanemometers was developed. These models use the finite volume method and k-e, k-wSST, SAS and GEKO turbulence models. A number of calculations were made using the selected turbulence models. An analysis of the flow conditions at the measurement site was carried out. Measurement and simulation results were compared. Based on the results obtained, plans for further in-situ experiments could be formulated.
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