o:1813 Nestacionarna strujanja u sistemima za transport tečnosti i njihova zaštita Unsteady flow in hydraulic transport systems and their protection: doctoral dissertation : doctoral dissertation sr The subject matter of this dissertation is a general analysis of unsteady flowsin hydraulic transport pipelines with a special focus on small hydropower pipelinesand the determination of dynamic properties of control valves and the stator. Thedetermined dynamic properties of governors and system behavior are verifiedthrough comparison with the measured results.The research subject and aims are defined based on the analysis of previousrelevant literature. Mathematical modelling of unsteady fluid flow in pipelines isconducted. The speed of pressure disturbance during water hammer is determinedand some basic cases of this phenomenon are presented. Based on the review ofavailable methods that significantly contributed to the study of this phenomenon,the method of characteristics is deductively selected to solve the relevantdifferential equations with boundary and initial conditions, after which differentrepresentations of the friction factor are given. Based on market availability ofdifferent valve types, three of them are selected; calculations and analyses of thethree valves yielded results that were then used to propose the best valve typewater hammer mitigation. Afterward, the basic parameters of water turbines aredescribed and a classification is provided for the turbines, for which linear anduniversal characteristics are then determined according to the main universalcharacteristic and the use of universal characteristics to obtain Suter curves isdemonstrated. Water hammer is modelled for systems containing a Pelton and aFrancis turbine and the results for specific small hydropower plants are thenverified against the modelling results. The dissertation also discusses potentialstatic and hydrodynamic methods of leakage detection in hydraulic transportsystems, with special focus on the method of pressure gradient analysis, which isthen supplemented with unsteady analyses for intentionally created pressuredisturbances in the system.Based on the developed models for establishing the dynamic properties oftransients, a procedure is proposed for identifying leakage and leakage locations ina hydraulic system. The obtained results will be used to formulaterecommendations for improved reliability and system protection. Biografija autora: str. 201-202,Bibliografija: str. 190-199. Datum odbrane: 22.02.2022. Unsteady Fluid Flow 91552100 62865161 91552101 8545 2022-11-29T11:17:06.053Z 45 no 46 Milica, Nikodijević 52850441 2021 63 mentor Jasmina, 1975- Bogdanović-Jovanović 1359207 2021 63 član komisije Darko, 1969- Mihajlov 14237287 2021 63 član komisije Uroš, 1974- Karadžić 62622473 2021 63 član komisije Živan Spasić 17096295 2021 [9], 201 str. 5194869 http://phaidrani.ni.ac.rs/o:1813 no yes 12 2022-11-29T11:17:06.320Z 70 Nestacionarno strujanje fluida, hidraulički udar, hidraulički zatvarači, zakonizatvaranja zatvarača, modeliranje hidrauličkog udara, Pelton–ova turbina, Francis–ova turbina, curenje tečnosti, lokacija curenja unsteady fluid flow, water hammer, hydraulic valves, valve closing laws, waterhammer modelling, Pelton turbine, Francis turbine, leakage flow, leakage location 621.643(043.3) T 210 1738 18A04 18A0404 2021