FULLY COUPLED COMPUTER SIMULATIONS OF A FLOW DRIVEN DARRIEUS TURBINE

Za pridobivanje energije iz vodotokov se v zadnjem času uporabljajo tudi turbine, ki so postavljene prosto v tok in predstavljajo bistveno manjši poseg v prostor kot običajne elektrarne. Postopki za preračun zmogljivosti tovrstnih turbin temeljijo na različnih aerodinamičnih modelih, medtem ko so se metode računalniške dinamike tekočin na tem področju pričele uporabljati šele pred kratkim. Tudi slednje se izvajajo z vnaprej predpisanimi parametri, ki predstavljajo predvideno ustaljeno obratovanje turbine. Za določanje obratovalne karakteristike je tako potrebno več simulacij pri različnih obratovalnih parametrih. Za poglobljeno razumevanje delovanja teh turbin so bili razviti novi pristopi računalniških simulacij, ki zajemajo pristop s tokom gnane turbine, kar predstavlja bistveno bolj realne pogoje v simulaciji. S tem pristopom je mogoče z eno simulacijo napovedati celotno obratovalno karakteristiko za določeno hitrost toka. S takšnim pristopom so bile izvedene parametrične simulacije geometrijskih parametrov turbine. Lopatice tovrstnih turbin, posebej pri namestitvi z vodoravno osjo vrtenja, predstavljajo dolge in vitke strukture, ki so med obratovanjem izpostavljene vodnemu toku. Ta vpliva na njihovo deformacijo, slednja pa na obtekanje lopatice. Posledica tega so spremembe v zmogljivostih turbine. Z uporabo kombinacije pristopa s tokom gnane turbine in močno vezanih simulacij medsebojnega vpliva tekočine in strukture je mogoče ovrednotiti vpliv deformacije lopatic na zmogljivosti turbine. Zato je bila razvita programska rutina, ki omogoča hkratno uporabo pristopa s tokom gnane turbine in močno vezanih simulacij. Za validacijo na novo razvitih postopkov simulacije je bil izveden eksperiment s pomanjšanim modelom turbine na naravnem vodotoku, pri katerem so bili izmerjeni povesi lopatice med obratovanjem turbine. Rezultati eksperimenta in simulacij so pokazali dobro ujemanje. Primerjava rezultatov simulacij izvedenih z uveljavljenimi postopki in na novo razvitimi pristopi je pokazala na znatne razlike v delovanju turbine, zato je smiseln nadaljnji razvoj in uporaba na novo razvitih pristopov.Among conventional systems for river energy extraction the new types of turbines are considered in the recent time that can be deployed in a free stream without impounding of a waterway and represent a minor impact on an environment when compared to conventional power stations. Procedures for analysis of these turbines are based on different aerodynamic models, while modern methods based on computational fluid dynamics have been applied only recently. Even those are performed using prescribed operational parameters, such as constant rotational velocity. To acquire the whole operational characteristics more simulations have to be performed. For a deeper understanding of operating principles the new simulation procedure has been developed, which employ flow driven approach, which enables more realistic condition in a simulation. Using such approach it is possible to acquire the whole operational characteristics of a turbine for a certain flow velocity within a single simulation. The blades of such turbines, especially in horizontal axis position, represent long and slender structures that are exposed to hydrodynamic loading during operation. This causes blade deformation, which instantly changes flow conditions around it. The consequence is altered performance of a turbine. Using a combination of flow driven approach and fully coupled fluid structure interaction in a simulation it is possible to assess the influence of blade deformation to the turbine performance. Therefore the routine has been developed to enable simultaneous use of fluid structure interaction and a flow driven approach. To validate the newly developed simulation procedures the experiment with a scaled model of a turbine was performed on a natural waterway. The results of experiment and simulation showed a good agreement. Comparison of simulations based on conventional and newly developed approaches pointed considerable differences in turbine operation. Therefore it is reasonable to use developed simulation procedure as well as its further development

Comparison of CFD simulation of Darrieus water turbine using the rigid body solver and the MFR method

Med tehnologijami za izkoriščanje vodne energije se vse pogosteje uporabljajo tudi prilagojene tehnologije za izkoriščanje energije vetra. K njihovemu razvoju pripomorejo sodobne računalniške simulacije. Predstavljena je primerjava dveh metod numerične simulacije Darrieusove turbine s poudarkom na ustreznosti delovanja nove metode z uporabo modela gibanja togega telesa (modul 6DOF). Ta omogoča simulacijo turbine, pri kateri je le-ta gnana s tokom tekočine, se pravi, da bolje opiše realne obratovalne razmere kot uveljavljen postopek MFR.Among technologies for stream energy extraction there are new emerging technologies using adapted wind energy extraction technologies. Their development is enhanced by using modern computer simulations. This document presents a comparison between two methods for numerical simulation of Darrieus turbine with emphasis on the suitability of the new rigid body solver. It enables the simulation of a turbine that is flowdriven, which better describes the real operating conditions than the MFR method