1. Pressurized Water Nuclear Reactor Downcomer Flow Simulation : diplomsko deloAljaž Kekec, 2021, diplomsko delo Opis: In the diploma thesis the flow pattern and conditions in the downcomer of a pressurized water nuclear reactor were simulated, to study coolant mixing inside the primary circuit. This was done using computational dynamics software Ansys CFX. The nuclear reactor in Krško (Slovenia) was used as a basis for the model. The downcomer geometry was simplied for a more feasible study. Three separate simulations were done: one with normal conditions, one with loss of coolant accident conditions and one with a modified geometry. The flow was then studied at different condition at the same levels using velocity contours. The results showed that the axial velocity profiles at the downcomer outlet are not completely uniform.
Ključne besede: Nuclear Power Plant, Pressurized Water Reactor, Downcomer, Flow simulation, Ansys CFX
Objavljeno v DKUM: 13.10.2021; Ogledov: 508; Prenosov: 47
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3. Synergies between an observed port and a logistic company : application of the discounted cash-flow model and the Monte Carlo simulationDejan Dragan, Bojan Rosi, Toni Avžner, 2017, izvirni znanstveni članek Opis: The paper addresses an analysis of potential synergies in collaboration between an observed Port in the Mediterranean Sea and Central-European logistic railway-services based company. Both companies have established a strategic partnership. The main motive was cooperation in rail transport, with a particular emphasis on potential synergies that would a rail traffic have brought to a port's business. For the purpose of synergies valuation under uncertain conditions, a Monte Carlo simulation-based framework with integrated discounted cash flow (DCF) model is applied. The possible values of future synergies are calculated via the DCF model by simultaneously changing values of different uncertain financial parameters at each repetition of a Monte Carlo scenario-playing mechanism. In this process, predicted forecasts of future synergetic throughputs are also used for various types of observed cargo. As it turned out, the generated synergies' values follow the approximate normal distribution. Based on statistical inference and analysis of probability intervals it was discovered that there might indeed exist certain important synergies in the collaboration between both companies. This fact has convinced us into a belief in the correctness of companies' decision to enter into such kind of strategic cooperation.
Ključne besede: port economics, financial management, valuation, discounted cash-flow model, Monte Carlo simulation, logistics
Objavljeno v DKUM: 06.07.2017; Ogledov: 1244; Prenosov: 225
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4. Roundabout arm capacity determined by microsimulation and discrete functions techniqueTomaž Tollazzi, Matjaž Šraml, Tone Lerher, 2008, izvirni znanstveni članek Opis: The paper demonstrates the influence of the multi-channel pedestrian flow on the actual capacity of a one-lane roundabout, using micro-simulation and discrete functions. The proposed model is based on the theory of the expected time gap between the units of pedestrian traffic flow, which have the priority when crossing the arm of the roundabout. The proposed model represents an upgrade of the previous research in the field of modelling traffic flows in the one-lane roundabout.Apart from the multi-channel pedestrian flow the disturbances caused by the circular traffic flow of motorised vehicles at the roundabout are also considered. In this way the model can better illustrate the real conditions in traffic. A simulation analysis has been performed on the roundabout arm at Koroška Street in Maribor. The results of the analysis have indicated a relatively high reserve of the actual throughput capacity for the main motorized traffic flow in the analysed roundabout arm. The presented model represents a practicable and adaptable tool for planning the roundabout capacity in practice and for the sensitivity analysis of individual variables on the throughput capacity of the roundabout.
Ključne besede: roundabouts, traffic flow analysis, micro-simulation modelling, capacity analysis
Objavljeno v DKUM: 05.06.2017; Ogledov: 1202; Prenosov: 137
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5. Določitev tokovnih karakteristik ejektorja za medicinske namene s pomočjo numerične simulacijeAleš Jakoša, 2016, diplomsko delo Opis: V diplomskem delu je predstavljena uporaba programskega paketa Solidworks Flow Simulation pri analizi in določitvi tokovnih karakteristik ejektorja za medicinske namene, naprave, ki ustvari sesanje po Venturijevem principu, ter določitev vpliva gostote mreže na rezultate numerične simulacije. Na obravnavanem ejektorju so bile najprej narejene meritve pretoka in podtlaka, ki so služile primerjavi rezultatov z numerično simulacijo. Numerična simulacija je bila narejena za dva različna režima z drugačnim robnim pogojem, s prvim je bil izračunan pretok, z drugim pa podtlak. Za vsak režim so bile zmodelirane tri različno goste mreže. Z Richardsonovo ekstrapolacijo je bila izračunana numerična negotovost in s tem določen vpliv gostote mreže na rezultate simulacije. Uporabljeno računalniško orodje se je izkazalo za učinkovito pri reševanju inženirskih problemov s področja toka tekočin.
Ključne besede: ejektor, računalniška dinamika tekočin, konstruiranje, SolidWorks Flow Simulation, Richardsonova ekstrapolacija
Objavljeno v DKUM: 13.09.2016; Ogledov: 1123; Prenosov: 145
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7. Computer-aided analysis of the forging processMatjaž Šraml, Janez Stupan, Iztok Potrč, Janez Kramberger, 2004, izvirni znanstveni članek Opis: This paper presents computer simulation of the forging process using the finite volume method (FVM). The process of forging is highly non-linear, where both large deformations and continuously changing boundary conditions occur. In most practical cases, the initial billet shape is relatively simple, but the final shape of the end product is often geometrically complex, to the extent that it is commonly obtained using multiple forming stages. Examples of the numerical simulation of the forged pieces provided were created using Msc/SuperForge computer code. The main results of the analysis are deformed shape, temperature, pressure, effective plastic strain, effective stress and forces acting on the die.
Ključne besede: forging, computer simulation, finite volume method, deformation, stresses, material flow, industrial applications
Objavljeno v DKUM: 01.06.2012; Ogledov: 1702; Prenosov: 103
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8. The use of micro-simulation in determining the capacity of a roundabout with a multi-channel pedestrian flowTomaž Tollazzi, Tone Lerher, Matjaž Šraml, 2008, izvirni znanstveni članek Opis: The main purpose of this paper is to analyse the influence of the multi-channel pedestrian flow on the capacity of the one-lane roundabout, using discrete simulation methods. The proposed model is based on the theory of the expected time void between the units of pedestrian traffic flow, which have the priority when crossing the arm of the roundabout. The proposed model represents an upgrade of the previous research in the field of modelling traffic flows in the one-lane roundabout. While the previous model of the pedestrian crossing is handled as the single-channel system in which the pedestrians arrive randomly from one side of the pedestrian crossing only, the proposed model deals with the multi-channel system in which the pedestrians arrive randomly from both sides of the pedestrian crossing. In thi sway the mathematical model can better illustrate the real conditions. The previous model considers only the disturbances of entry traffic flow of motorised vehicles caused by the pedestrian flow crossing the roundabout arm. The proposed model considers the disturbances caused by the circular traffic flow of motorised vehicles as well. A simulation analysis has been conducted on the roundabout at Koroška Street in Maribor, in which the counting of the motorised traffic flow and the pedestrian flow has been performed in the morning peek hour. The results of the analysis have indicated a high reserve of the capacity for pedestrians who arrive from the left and right sides of the roundabout with regard to motorised vehicles in the analysed arm of the roundabout. The real reserve of the capacity would otherwise be smaller in case of enlargement of the motorised vehicle flow in the future. Nevertheless it would be high enough for an undisturbed traffic flow of motorised vehicles through the roundabout to be possible. The presented methodology represents a practicable and adaptable tool for planning the roundabout capacity in practice and for the sensitivity analysis of individual variables on the throughput capacity of the roundabout.
Ključne besede: roundabout, pedestrian flow, traffic flow modeling, simulation models
Objavljeno v DKUM: 31.05.2012; Ogledov: 1777; Prenosov: 51
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9. Boundary element method for thermal flows using k-[epsilon] turbulence modelsMatjaž Ramšak, Leopold Škerget, 2008, objavljeni znanstveni prispevek na konferenci Opis: Purpose - This paper aims to develop a multidomain boundary element method (BEM) for modeling 2D complex turbulent thermal flow using low Reynolds two-equation turbulence models. Design/methodology/approach - The integral boundary domain equations are discretised using mixed boundary elements and a multidomain method also known as a subdomain technique. The resulting system matrix is an overdetermined, sparse block banded and solved using a fast iterative linear least squares solver. Findings - The simulation of a turbulent flow over a backward step is in excellent agreement with the finite volume method using the same turbulent model. A grid consisting of over 100,000 elements could be solved in the order of a few minutes using a 3.0 GhzP4 and 1 GB memory indicating good efficiency. Originality/value - The paper shows, for the first time, that the BEM is applicable to thermal flows using k-▫$epsilon$▫.
Ključne besede: thermal flow, heat exchange, turbulence, boundary element method, simulation
Objavljeno v DKUM: 31.05.2012; Ogledov: 1414; Prenosov: 42
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10. Velocity vorticity-based large eddy simulation with the bounadr element methodJure Ravnik, Leopold Škerget, Matjaž Hriberšek, 2006, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje) Opis: A large eddy simulation using the velocity-vorticity formulation of the incompressible Navier-Stokes equations in combination with the turbulent heat transfer equation is proposed for the solution of the turbulent natural convection drive flow in a 1:4 enclosure. The system of equations is closed by an enthropy-based subgrid scale model.The Prandtl turbulent number is used to estimate turbulent diffusion in the heat transfer equation. The boundary element method is used to solve the kinematics equation and estimate the boundary vorticity values. The vorticity transport equation is solved by FEM. The numerical example studied in this paper is the onset of a turbulent flow regime occuring at high Rayleigh number values ▫$(Ra=10^7-10^10)$▫. The formation of vortices in the boundary layer is observed, along with buoyancy driven diffusive convective transport. Quantitative comparison with the laminar flow model and the worh of other authors is also presented in terms of Nusselt number value oscillations.
Ključne besede: fluid mechanics, incompressible viscous fluid, turbulent flow, velocity vorticity formulation, finite element method, large eddy simulation
Objavljeno v DKUM: 31.05.2012; Ogledov: 1858; Prenosov: 35
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