Iskanje po katalogu digitalne knjižnice

Opis: Cavitation is the phenomenon of fluid evaporation in hydraulic systems, which occurs due to a pressure drop below the value of the vapor pressure. For numerical modelling of this generally undesirable phenomenon, which is often associated with material damage (erosion), there are various mathematical vapor transfer models that have been validated in the past. There are different approaches to predicting cavitation erosion, which have mostly been experimental in the past. Recently various numerical models have been developed with the development of numerical simulations. They describe the phenomenon of cavitation erosion based on different theoretical considerations, such as Pressure wave hypothesis, Microjet hypothesis, or a combination of both. In the present paper, an analysis of the Schnerr-Sauer transport cavitation model was used, upgraded with an erosive potential energy model based on pressure wave hypothesis for cavitation erosion prediction. The extended numerical model has been applied to the case of a radial divergent test section in three different mathematical formulations. The results of simulation were compared and validated to experimental work performed by other authors. The study shows that the distribution of surface accumulated energy agrees with the experimental results, although certain differences exist between formulations. The applied method appears to be appropriate for further use, and to be extended to materials response modelling in the future.
Ključne besede: kavitacija, erozija, erozivna potencialna energija, numerične simulacije, cavitation, erosion, erosive potential energy, numerical simulation
Objavljeno v DKUM: 26.03.2025; Ogledov: 0; Prenosov: 7
Povezava na celotno besedilo
Gradivo ima več datotek! Več...

Opis: In the past years various methods have been developed to estimate high-resolution solar potential in urban areas, by simulating solar irradiance over surface models that originate from remote sensing data. In general, this requires discretisation of solar irradiance models that estimate direct, reflective, and diffuse irradiances. The latter is most accurately estimated by an anisotropic model, where the hemispherical sky dome from arbitrary surface’s viewpoint consists of the horizon, the circumsolar and sky regions. Such model can be modified to incorporate the effects of shadowing from obstruction with a view factor for each sky region. However, state-of-the-art using such models for estimating solar potential in urban areas, only considers the sky view factor, and not circumsolar view factor, due to high computational load. In this paper, a novel parallelisation of solar potential estimation is proposed by using General Purpose computing on Graphics Processing Units (GPGPU). Modified anisotropic Perez model is used by considering diffuse shadowing with all three sky view factors. Moreover, we provide validation based on sensitivity analysis of the method’s accuracy with independent meteorological measurements, by changing circumsolar sky region’s half-angle and resolution of the hemispherical sky dome. Finally, the presented method using GPPGU was compared to multithreaded Central Processing Unit (CPU) approach, where on average a 70x computational speedup was achieved. Finally, the proposed method was applied over a urban area, obtained from Light Detection And Ranging (LiDAR) data, where the computation of solar potential was performed in a reasonable time.
Ključne besede: solar energy, solar potential, anisotropic diffuse irradiance, LiDAR, GPGPU
Objavljeno v DKUM: 17.12.2024; Ogledov: 0; Prenosov: 10
Celotno besedilo (8,06 MB)

Ključne besede: deep learning, fully convolutional neural network, LiDAR data, digital elevation model, solar energy, solar potential
Objavljeno v DKUM: 26.01.2024; Ogledov: 244; Prenosov: 118
Celotno besedilo (6,42 MB)
Gradivo ima več datotek! Več...

Opis: In this thesis we introduce the problem of the ideal homogeneous hanging cable called the catenary. We observe the behaviour of the shape of the curve. Firstly, we solve the problem of the classical catenary on a flfat Earth, where the gravitational fifield is constant and perpendicular to the ground. Secondly, we focus on the true symmetric catenary in the central gravitational fifield, which comes from the -1/r potential. In both cases we use the method of calculus of variations for isoperimetric problems and in particular the Euler-Lagrange difffferential equation. Lastly, we explain the problem of the asymmetric case.
Ključne besede: Catenary, calculus of variations, Euler-Lagrange equation, curvature, potential energy, difffferential equation.
Objavljeno v DKUM: 25.09.2013; Ogledov: 2336; Prenosov: 188
Celotno besedilo (571,58 KB)