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1.
Numerical analysis of a wind turbine blade with different software
Gorazd Hren, 2019, izvirni znanstveni članek

Opis: The development of wind power generation technology recognises the wind turbine blade design and manufacturing as crucial for its performance. The laboratory size wind turbine blade was analysed, considering the 3D printing plastic material for blades. Applying the structural dynamic equations of blades, the aero-elastic model of the rotating rotor and the numerical simulation method of the deflections are presented under the aerodynamic loads and centrifugal forces. Based on the parameters of aerofoil and the geometrical parameters of blade, 3D model of the blade was established with the modelling software. Then the model was introduced into computational flow dynamics software to carry out the loads on the blade and further into numerical structural analysis. The analysis was performed in two different software packages. Design of wind turbine blades depends on high precision, reliable and robust numerical predictions of performance where the plug-in software is found to be inadequate for nontrivial problems.
Ključne besede: computational fluid dynamics, numerical analysis, structural analysis, wind turbine blade
Objavljeno v DKUM: 22.02.2024; Ogledov: 142; Prenosov: 10
.pdf Celotno besedilo (1,68 MB)
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2.
Cavitation erosion modelling : comparison of different driving pressure approaches
Luka Kevorkijan, Marko Pezdevšek, Ignacijo Biluš, Gorazd Hren, 2023, izvirni znanstveni članek

Opis: In this paper we compared different driving pressure approaches to calculate the cavitation potential energy from a source, which is transferred to a surface. The first approach used the reference pressure, the second approach used the pressure calculated at each timestep with no averaging, the third approach used the averaged pressure values from all timesteps included in one shedding cycle, and the last approach used pressure values from the steady state simulations results. The results show that for all formulations the averaged pressure values and steady state pressure values give similar results in terms of mean potential power distribution on the hydrofoil surface as in absolute values. The reference pressure approach gave similar results for the derivative and divergence formulation while for the source term the mean potential power distribution on the hydrofoil surface differs and the maximums were near the leading edge. The approach where we used no pressure averaging gave adequate results in terms of mean potential power distribution but differs from other approaches in absolute values which were considerably lower for all potential power formulations.
Ključne besede: cavitation, erosion potentional, driving pressure, numerical simulations
Objavljeno v DKUM: 21.02.2024; Ogledov: 144; Prenosov: 3
.pdf Celotno besedilo (796,29 KB)
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3.
Primerjava sistemov CAD (Solidworks in Onshape) pri 3D modeliranju : diplomsko delo
Jan Gabrijel, 2023, diplomsko delo

Opis: Programska oprema za računalniško podprto konstruiranje je stalnica pri razvoju izdelkov in ima velik vpliv na različne tehnologije in sisteme proizvodnje v raznovrstnih panogah. Razvoj in uporaba teh sistemov je ključno spremenila tradicionalne metode razvoja izdelkov vse od prototipa do končne proizvodnje. Čeprav se teoretske metode modeliranja ne spreminjajo veliko, je njihov razvoj v zadnjem času predvsem usmerjen na prilagajanje vedno močnejši strojni opremi, kakovosti prikazovanja in predvsem soočanja s številnimi izzivi kot so dostopnost do skupnih podatkovnih baz, komunikacija preko računalniških mrež, težave z verzijami ter stroški strojne opreme in licenciranja. Novejša programska oprema CAD v oblaku, uporabnikom ponuja novo in drugačno storitev, ki ne zahteva namestitve programske opreme in licenciranje, in je enostavno dosegljiva iz internetnega prikazovalnika. Programska oprema v oblaku na splošno sicer še ne odgovarja na vsa vprašanja, ki se ob pojavljajo ob uporabi, vendar že prinaša nove pristope, ki nakazujejo smernice drugačne uporabe sistemov CAD. V diplomski nalogi smo na primeru geometrije sklopa parnega stroja primerjali sistema CAD: Solidwoks kot tradicionalni sistem CAD in Onshape kot primer sistema CAD v oblaku. Namen diplomske naloge je uporabniška izkušnja dveh programskih sistemov CAD na enakem izdelku katere rezultat so številni dejavniki, ki jih je potrebno upoštevati. Ugotovimo lahko, da je uporabniška izkušnja zelo podobna, a je prednost, ob zagotovljeni varnosti podatkov na strani oblačnih storitev.
Ključne besede: sistemi CAD, modeliranje, računalništvo v oblaku
Objavljeno v DKUM: 16.01.2024; Ogledov: 188; Prenosov: 13
.pdf Celotno besedilo (2,95 MB)

4.
Vizualizacija temperaturne porazdelitve na podlagi meritev : diplomsko delo
Katja Zapušek, 2023, diplomsko delo

Opis: Pri postavitvah novih in obnovi starejših prostorov je temperatura zelo pomemben dejavnik. S pomočjo senzorjev lahko temperaturo izmerimo in jo vizualno predstavimo v realnem 3D-prostoru. Prostor, ki ga predstavimo v končnem programu, razdelimo na enakomerno razporejene enote. Vsak senzor zavzema svojo enoto, ostale enote predstavljajo izračunane temperature skozi interpolacijo. V enotah so določene in izračunane temperature predstavljene z določeno barvo. Vsako posamezno enoto lahko tudi zmanjšamo. Z zmanjšanjem ene enote pridobimo gostejšo mrežo in natančnejšo sliko barv ter temperatur.
Ključne besede: prostorska računalniška vizualizacija, temperaturno polje, X3D
Objavljeno v DKUM: 16.01.2024; Ogledov: 108; Prenosov: 11
.pdf Celotno besedilo (2,27 MB)

5.
Influence of Numerical Mesh Type on Airfoil Aerodynamic Characteristics
Marko Pezdevšek, Matej Fike, Andrej Predin, Gorazd Hren, 2019, objavljeni znanstveni prispevek na konferenci

Opis: In this paper, we will examine how different mesh types affect the aerodynamic characteristic of an airfoil. The airfoil used for this paper was the NREL S809. Three different mesh types were created, a blocked structured mesh, an unstructured mesh and a hybrid mesh containing a blocked structured mesh near the surface of the airfoil and an unstructured mesh on the outside perimeter. Steady state simulations were performed for angles of attack between 0°and 22°. Lift and drag coefficient for all created meshes were compared to experimental results from literature. From angles of attack between 2° and 8° all three meshes predict similar lift and drag coefficients. We encountered problems with convergence for the unstructured mesh at angles of attack higher than 8°. Structured and hybrid mesh had similar lift and drag coefficients across all angles of attack.
Ključne besede: computational fluid dynamics, NREL S809, structured mesh, unstructured mesh, hybrid mesh
Objavljeno v DKUM: 04.12.2023; Ogledov: 216; Prenosov: 9
.pdf Celotno besedilo (18,06 MB)
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6.
Experimental and Numerical Research of Micro Wind Turbine for Low Wind Speeds
Matej Fike, Marko Pezdevšek, Andrej Predin, Gorazd Hren, 2019, objavljeni znanstveni prispevek na konferenci

Opis: In this paper, experimental and numerical study of micro wind turbine for low wind speeds is presented. Numerical simulations were performed for two turbines with different blades at various wind speeds. The first geometry was NTNU turbine and the second was modified NTNU turbine with shorter blades. Results from the numerical study showed that more efficient with higher power coefficient is turbine with modified blades.
Ključne besede: wind turbine, NREL S826, CFD, power coefficient, structured mesh
Objavljeno v DKUM: 04.12.2023; Ogledov: 181; Prenosov: 8
.pdf Celotno besedilo (18,06 MB)
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7.
Methodology of immersive video application : the case study of a virtual tour
Jure Jazbinšek, Gorazd Hren, 2021, izvirni znanstveni članek

Opis: A Virtual Tour is an interactive presentation of real places accessible directly with an Internet browser with no additional installations of apps of plugins. Once, 360° photos are recorded and processed (stitched into spherical panoramas), editing of a Virtual Tour (walk) enables connection of spherical panoramic photos (or videos) into interactive presentations. For an enhanced experience and stand-alone presenting ability, features are added, like natural-sounding voice for text-to-speech descriptions and embedded videos. During multiple virtual tour presentations, users, viewers and presenters reported exceptional usability and an immersive experience. Virtual Tours have great potential to reshape the future education process and establish a new benchmark for presentation. The Virtual Tours application is expected to be used in education, tourism and future building sites or industry, as a key component for workforce briefings, and “as build” documenting of various stages of build, with the possibilities to integrate into Building Information Modelling (BIM) models.
Ključne besede: virtual tour, 360 camera, RICOH THETA Z1, 3dVista, Text to Speech
Objavljeno v DKUM: 13.11.2023; Ogledov: 270; Prenosov: 3
.pdf Celotno besedilo (2,21 MB)
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8.
Static model of temperature distribution in a photovoltaic module
Klemen Sredenšek, Sebastijan Seme, Gorazd Hren, 2021, izvirni znanstveni članek

Opis: The primary objective of this paper is to present a static model for calculating the temperature distribution in a photovoltaic module using the finite element method. The paper presents in more detail the theoretical background of solar radiation, heat transfer, and the finite element method. The results of the static model are evaluated using temperature measurements of a photovoltaic model, which were performed at the Institute of Energy Technology, Faculty of Energy Technology, University of Maribor. The results of the regression analysis show a good concurrence between the measured and modelled values of the temperature of the photovoltaic module, especially on days with a higher share of the direct component of solar radiation.
Ključne besede: photovoltaic module, temperature distribution, heat transfer, finite element method
Objavljeno v DKUM: 13.11.2023; Ogledov: 148; Prenosov: 5
.pdf Celotno besedilo (2,01 MB)
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9.
Lost Energy of Water Spilled over Hydropower Dams
Andrej Predin, Matej Fike, Marko Pezdevšek, Gorazd Hren, 2021, izvirni znanstveni članek

Opis: The present paper presents a view of water spilled over hydropower plants as an energy loss. In the current climate conditions, flood events are becoming more frequent due to human impact on the environment; water spills are also more frequent, which means more and more energy is lost. How much water is spilled and, consequently, how much energy is lost is shown in the present article on the chain of power plants on the Sava River in the five years from 2015 to 2019. An analytical assessment of the current situation in the lock was carried out, which showed that the available water through the locks could be used efficiently. The paper presents a case study of one overflow event lasting 48 h. The calculated theoretical losses of energy (of spilled water) and possible technical implementation for capturing losses are given. The proposed technical implementation is based on established technology, so we could expect that the approach is feasible. The results show that the estimated spilled water energy potential reaches about 40% of the actual spilled water or energy lost.
Ključne besede: energy loss, spilled water energy, hydropower
Objavljeno v DKUM: 13.11.2023; Ogledov: 139; Prenosov: 10
.pdf Celotno besedilo (9,63 MB)
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10.
Comparison of cavitation models for the prediction of cavitation around a hydrofoil
Marko Pezdevšek, Ignacijo Biluš, Gorazd Hren, 2021, izvirni znanstveni članek

Opis: In this paper, four different cavitation models were compared for predicting cavitation around a hydrofoil. A blocked structured mesh was created in ICEM CFD. Steady-state 2D simulations were performed in Ansys CFX. For all cases, the SST turbulence model with Reboud's correction was used. For Zwart and Schnerr cavitation models, the recommended values were used for the empirical coefficients. For the full cavitation model and Kunz cavitation model, values for the empirical coefficients were determined as the recommended values did not provide satisfactory results. For the full cavitation model, the effect of non-condensable gases was neglected. For all the above-mentioned cavitation models, the pressure coefficient distribution was compared to experimental results from the literature.
Ključne besede: hydrofoil, cavitation, Ansys CFX
Objavljeno v DKUM: 10.11.2023; Ogledov: 262; Prenosov: 6
.pdf Celotno besedilo (1,90 MB)
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