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V diplomski nalogi je opisan primer matematičnega modeliranja turbulentnega toka v ribji stezi s programom PCFLOW2D. V zadnjem času se v Sloveniji posveča vedno večja pozornost raziskavam za izboljšanje vzdolžne povezljivosti vodotokov za doseganje dobrega ekološkega stanja, ki ga zahteva Vodna direktiva za vse stare in nove ribje steze do leta 2027. Pri tem lahko uporabimo tudi izračune s hidravličnimi modeli, ki pomagajo pri določevanju tokovne slike, s katero bomo ocenili primernost ribjih stez za ribje migracije. V prvem delu naloge se najprej predstavi glavne lastnosti najpogostejših tipov ribjih stez v svetu in našteje njihove dobre in slabe lastnosti, vključno z vprašanjem postavitve na pregradi. Razložen je pomen uspešnosti ribje steze in možnosti izboljšav našega razumevanja dogajanja na osnovi zbirke standardiziranih meritev migracij. V drugem delu naloge je obravnavana steza z vertikalno režo na HE Arto Blanca. Ker je tok izrazito dvodimenzionalen smo za simulacijo toka uporabili globinsko povprečni model PCFLOW2D z vgrajenim k-ε modelom turbulence. Izračun petih različnih primerov pretokov in štirih vzdolžnih padcev je pokazal, da je stopnja turbulence v stezi v največji meri odvisna od spremembe padca. Pri ugotavljanju primernost toka v stezi za ribe se izkaže, da imajo dovolj nizke vrednosti disipacije turbulentne kinetične energije le primeri z najmanjšim vzdolžnim padcem 10 cm na prekat ribje steze. This thesis discussses the use of mathematical modeling of a turbulent flow using PCFLOW2D in a fishway. Recently in Slovenia they gained increased attention for the research of the improval of the longitudinal connectivity of watercourses to achieve good ecological status required by Water Framework Directive for all existing and new fishways by the year of 2027. We can therefore use hydraulic models to calculate different flow conditions of various fishway examples to assess their suitability for fish migration. In the first part of the thesis we present the main features of the most common types of fishways currently used in the world and list their strengths and weaknesses. We then explain the importance of efficient fishways and how it could improve our understanding by collecting large data of standardized measurements of migrations on existing fishways. In the second part of the thesis we use the example of the vertical slot fishway used on HPP Arto Blanca. Its flow can be described as an example of a two dimensional flow. where the vertical component of the velocity is negligible, therefore we use depth-averged model of flow for the existing two planar velocity components. We perform our calculations with the k-ε turbulence model on four different examples of longitudinal slopes in five different flow conditions, which shows that the degree of turbulence is only slope dependent. When checking the suitability for target fish species it turns out that only the lowest level of longitudinal slope of 10 cm per pool gets sufficient enough low levels of dissipation of the turbulent kinetic energy. |
